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diff --git a/gcc-4.9/gcc/doc/gcj.info b/gcc-4.9/gcc/doc/gcj.info deleted file mode 100644 index cd5c9b161..000000000 --- a/gcc-4.9/gcc/doc/gcj.info +++ /dev/null @@ -1,3653 +0,0 @@ -This is gcj.info, produced by makeinfo version 5.1 from gcj.texi. - -Copyright (C) 2001-2014 Free Software Foundation, Inc. - - Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, the Front-Cover Texts being (a) (see below), and -with the Back-Cover Texts being (b) (see below). A copy of the license -is included in the section entitled "GNU Free Documentation License". - - (a) The FSF's Front-Cover Text is: - - A GNU Manual - - (b) The FSF's Back-Cover Text is: - - You have freedom to copy and modify this GNU Manual, like GNU -software. Copies published by the Free Software Foundation raise funds -for GNU development. -INFO-DIR-SECTION Software development -START-INFO-DIR-ENTRY -* Gcj: (gcj). Ahead-of-time compiler for the Java language -END-INFO-DIR-ENTRY - -INFO-DIR-SECTION Individual utilities -START-INFO-DIR-ENTRY -* jcf-dump: (gcj)Invoking jcf-dump. - Print information about Java class files -* gij: (gcj)Invoking gij. GNU interpreter for Java bytecode -* gcj-dbtool: (gcj)Invoking gcj-dbtool. - Tool for manipulating class file databases. -* jv-convert: (gcj)Invoking jv-convert. - Convert file from one encoding to another -* grmic: (gcj)Invoking grmic. - Generate stubs for Remote Method Invocation. -* gc-analyze: (gcj)Invoking gc-analyze. - Analyze Garbage Collector (GC) memory dumps. -* aot-compile: (gcj)Invoking aot-compile. - Compile bytecode to native and generate databases. -* rebuild-gcj-db: (gcj)Invoking rebuild-gcj-db. - Merge the per-solib databases made by aot-compile - into one system-wide database. -END-INFO-DIR-ENTRY - - - Copyright (C) 2001-2014 Free Software Foundation, Inc. - - Permission is granted to copy, distribute and/or modify this document -under the terms of the GNU Free Documentation License, Version 1.3 or -any later version published by the Free Software Foundation; with no -Invariant Sections, the Front-Cover Texts being (a) (see below), and -with the Back-Cover Texts being (b) (see below). A copy of the license -is included in the section entitled "GNU Free Documentation License". - - (a) The FSF's Front-Cover Text is: - - A GNU Manual - - (b) The FSF's Back-Cover Text is: - - You have freedom to copy and modify this GNU Manual, like GNU -software. Copies published by the Free Software Foundation raise funds -for GNU development. - - -File: gcj.info, Node: Top, Next: Copying, Up: (dir) - -Introduction -************ - -This manual describes how to use 'gcj', the GNU compiler for the Java -programming language. 'gcj' can generate both '.class' files and object -files, and it can read both Java source code and '.class' files. - -* Menu: - -* Copying:: The GNU General Public License -* GNU Free Documentation License:: - How you can share and copy this manual -* Invoking gcj:: Compiler options supported by 'gcj' -* Compatibility:: Compatibility between gcj and other tools for Java -* Invoking jcf-dump:: Print information about class files -* Invoking gij:: Interpreting Java bytecodes -* Invoking gcj-dbtool:: Tool for manipulating class file databases. -* Invoking jv-convert:: Converting from one encoding to another -* Invoking grmic:: Generate stubs for Remote Method Invocation. -* Invoking gc-analyze:: Analyze Garbage Collector (GC) memory dumps. -* Invoking aot-compile:: Compile bytecode to native and generate databases. -* Invoking rebuild-gcj-db:: Merge the per-solib databases made by aot-compile - into one system-wide database. -* About CNI:: Description of the Compiled Native Interface -* System properties:: Modifying runtime behavior of the libgcj library -* Resources:: Where to look for more information -* Index:: Index. - - -File: gcj.info, Node: Copying, Next: GNU Free Documentation License, Prev: Top, Up: Top - -GNU General Public License -************************** - - Version 3, 29 June 2007 - - Copyright (C) 2007 Free Software Foundation, Inc. <http://fsf.org/> - - Everyone is permitted to copy and distribute verbatim copies of this - license document, but changing it is not allowed. - -Preamble -======== - -The GNU General Public License is a free, copyleft license for software -and other kinds of works. - - The licenses for most software and other practical works are designed -to take away your freedom to share and change the works. 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Interpretation of Sections 15 and 16. - - If the disclaimer of warranty and limitation of liability provided - above cannot be given local legal effect according to their terms, - reviewing courts shall apply local law that most closely - approximates an absolute waiver of all civil liability in - connection with the Program, unless a warranty or assumption of - liability accompanies a copy of the Program in return for a fee. - -END OF TERMS AND CONDITIONS -=========================== - -How to Apply These Terms to Your New Programs -============================================= - -If you develop a new program, and you want it to be of the greatest -possible use to the public, the best way to achieve this is to make it -free software which everyone can redistribute and change under these -terms. - - To do so, attach the following notices to the program. It is safest -to attach them to the start of each source file to most effectively -state the exclusion of warranty; and each file should have at least the -"copyright" line and a pointer to where the full notice is found. - - ONE LINE TO GIVE THE PROGRAM'S NAME AND A BRIEF IDEA OF WHAT IT DOES. - Copyright (C) YEAR NAME OF AUTHOR - - This program is free software: you can redistribute it and/or modify - it under the terms of the GNU General Public License as published by - the Free Software Foundation, either version 3 of the License, or (at - your option) any later version. - - This program is distributed in the hope that it will be useful, but - WITHOUT ANY WARRANTY; without even the implied warranty of - MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - General Public License for more details. - - You should have received a copy of the GNU General Public License - along with this program. If not, see <http://www.gnu.org/licenses/>. - - Also add information on how to contact you by electronic and paper -mail. - - If the program does terminal interaction, make it output a short -notice like this when it starts in an interactive mode: - - PROGRAM Copyright (C) YEAR NAME OF AUTHOR - This program comes with ABSOLUTELY NO WARRANTY; for details type 'show w'. - This is free software, and you are welcome to redistribute it - under certain conditions; type 'show c' for details. - - The hypothetical commands 'show w' and 'show c' should show the -appropriate parts of the General Public License. Of course, your -program's commands might be different; for a GUI interface, you would -use an "about box". - - You should also get your employer (if you work as a programmer) or -school, if any, to sign a "copyright disclaimer" for the program, if -necessary. For more information on this, and how to apply and follow -the GNU GPL, see <http://www.gnu.org/licenses/>. - - The GNU General Public License does not permit incorporating your -program into proprietary programs. If your program is a subroutine -library, you may consider it more useful to permit linking proprietary -applications with the library. If this is what you want to do, use the -GNU Lesser General Public License instead of this License. But first, -please read <http://www.gnu.org/philosophy/why-not-lgpl.html>. - - -File: gcj.info, Node: GNU Free Documentation License, Next: Invoking gcj, Prev: Copying, Up: Top - -GNU Free Documentation License -****************************** - - Version 1.3, 3 November 2008 - - Copyright (C) 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc. - <http://fsf.org/> - - Everyone is permitted to copy and distribute verbatim copies - of this license document, but changing it is not allowed. - - 0. PREAMBLE - - The purpose of this License is to make a manual, textbook, or other - functional and useful document "free" in the sense of freedom: to - assure everyone the effective freedom to copy and redistribute it, - with or without modifying it, either commercially or - noncommercially. Secondarily, this License preserves for the - author and publisher a way to get credit for their work, while not - being considered responsible for modifications made by others. - - This License is a kind of "copyleft", which means that derivative - works of the document must themselves be free in the same sense. - It complements the GNU General Public License, which is a copyleft - license designed for free software. - - We have designed this License in order to use it for manuals for - free software, because free software needs free documentation: a - free program should come with manuals providing the same freedoms - that the software does. But this License is not limited to - software manuals; it can be used for any textual work, regardless - of subject matter or whether it is published as a printed book. We - recommend this License principally for works whose purpose is - instruction or reference. - - 1. APPLICABILITY AND DEFINITIONS - - This License applies to any manual or other work, in any medium, - that contains a notice placed by the copyright holder saying it can - be distributed under the terms of this License. Such a notice - grants a world-wide, royalty-free license, unlimited in duration, - to use that work under the conditions stated herein. The - "Document", below, refers to any such manual or work. Any member - of the public is a licensee, and is addressed as "you". You accept - the license if you copy, modify or distribute the work in a way - requiring permission under copyright law. - - A "Modified Version" of the Document means any work containing the - Document or a portion of it, either copied verbatim, or with - modifications and/or translated into another language. - - A "Secondary Section" is a named appendix or a front-matter section - of the Document that deals exclusively with the relationship of the - publishers or authors of the Document to the Document's overall - subject (or to related matters) and contains nothing that could - fall directly within that overall subject. (Thus, if the Document - is in part a textbook of mathematics, a Secondary Section may not - explain any mathematics.) The relationship could be a matter of - historical connection with the subject or with related matters, or - of legal, commercial, philosophical, ethical or political position - regarding them. - - The "Invariant Sections" are certain Secondary Sections whose - titles are designated, as being those of Invariant Sections, in the - notice that says that the Document is released under this License. - If a section does not fit the above definition of Secondary then it - is not allowed to be designated as Invariant. The Document may - contain zero Invariant Sections. If the Document does not identify - any Invariant Sections then there are none. - - The "Cover Texts" are certain short passages of text that are - listed, as Front-Cover Texts or Back-Cover Texts, in the notice - that says that the Document is released under this License. A - Front-Cover Text may be at most 5 words, and a Back-Cover Text may - be at most 25 words. - - A "Transparent" copy of the Document means a machine-readable copy, - represented in a format whose specification is available to the - general public, that is suitable for revising the document - straightforwardly with generic text editors or (for images composed - of pixels) generic paint programs or (for drawings) some widely - available drawing editor, and that is suitable for input to text - formatters or for automatic translation to a variety of formats - suitable for input to text formatters. A copy made in an otherwise - Transparent file format whose markup, or absence of markup, has - been arranged to thwart or discourage subsequent modification by - readers is not Transparent. An image format is not Transparent if - used for any substantial amount of text. A copy that is not - "Transparent" is called "Opaque". - - Examples of suitable formats for Transparent copies include plain - ASCII without markup, Texinfo input format, LaTeX input format, - SGML or XML using a publicly available DTD, and standard-conforming - simple HTML, PostScript or PDF designed for human modification. - Examples of transparent image formats include PNG, XCF and JPG. - Opaque formats include proprietary formats that can be read and - edited only by proprietary word processors, SGML or XML for which - the DTD and/or processing tools are not generally available, and - the machine-generated HTML, PostScript or PDF produced by some word - processors for output purposes only. - - The "Title Page" means, for a printed book, the title page itself, - plus such following pages as are needed to hold, legibly, the - material this License requires to appear in the title page. For - works in formats which do not have any title page as such, "Title - Page" means the text near the most prominent appearance of the - work's title, preceding the beginning of the body of the text. - - The "publisher" means any person or entity that distributes copies - of the Document to the public. - - A section "Entitled XYZ" means a named subunit of the Document - whose title either is precisely XYZ or contains XYZ in parentheses - following text that translates XYZ in another language. (Here XYZ - stands for a specific section name mentioned below, such as - "Acknowledgements", "Dedications", "Endorsements", or "History".) - To "Preserve the Title" of such a section when you modify the - Document means that it remains a section "Entitled XYZ" according - to this definition. - - The Document may include Warranty Disclaimers next to the notice - which states that this License applies to the Document. These - Warranty Disclaimers are considered to be included by reference in - this License, but only as regards disclaiming warranties: any other - implication that these Warranty Disclaimers may have is void and - has no effect on the meaning of this License. - - 2. VERBATIM COPYING - - You may copy and distribute the Document in any medium, either - commercially or noncommercially, provided that this License, the - copyright notices, and the license notice saying this License - applies to the Document are reproduced in all copies, and that you - add no other conditions whatsoever to those of this License. You - may not use technical measures to obstruct or control the reading - or further copying of the copies you make or distribute. However, - you may accept compensation in exchange for copies. If you - distribute a large enough number of copies you must also follow the - conditions in section 3. - - You may also lend copies, under the same conditions stated above, - and you may publicly display copies. - - 3. COPYING IN QUANTITY - - If you publish printed copies (or copies in media that commonly - have printed covers) of the Document, numbering more than 100, and - the Document's license notice requires Cover Texts, you must - enclose the copies in covers that carry, clearly and legibly, all - these Cover Texts: Front-Cover Texts on the front cover, and - Back-Cover Texts on the back cover. Both covers must also clearly - and legibly identify you as the publisher of these copies. The - front cover must present the full title with all words of the title - equally prominent and visible. You may add other material on the - covers in addition. Copying with changes limited to the covers, as - long as they preserve the title of the Document and satisfy these - conditions, can be treated as verbatim copying in other respects. - - If the required texts for either cover are too voluminous to fit - legibly, you should put the first ones listed (as many as fit - reasonably) on the actual cover, and continue the rest onto - adjacent pages. - - If you publish or distribute Opaque copies of the Document - numbering more than 100, you must either include a machine-readable - Transparent copy along with each Opaque copy, or state in or with - each Opaque copy a computer-network location from which the general - network-using public has access to download using public-standard - network protocols a complete Transparent copy of the Document, free - of added material. If you use the latter option, you must take - reasonably prudent steps, when you begin distribution of Opaque - copies in quantity, to ensure that this Transparent copy will - remain thus accessible at the stated location until at least one - year after the last time you distribute an Opaque copy (directly or - through your agents or retailers) of that edition to the public. - - It is requested, but not required, that you contact the authors of - the Document well before redistributing any large number of copies, - to give them a chance to provide you with an updated version of the - Document. - - 4. MODIFICATIONS - - You may copy and distribute a Modified Version of the Document - under the conditions of sections 2 and 3 above, provided that you - release the Modified Version under precisely this License, with the - Modified Version filling the role of the Document, thus licensing - distribution and modification of the Modified Version to whoever - possesses a copy of it. In addition, you must do these things in - the Modified Version: - - A. Use in the Title Page (and on the covers, if any) a title - distinct from that of the Document, and from those of previous - versions (which should, if there were any, be listed in the - History section of the Document). You may use the same title - as a previous version if the original publisher of that - version gives permission. - - B. List on the Title Page, as authors, one or more persons or - entities responsible for authorship of the modifications in - the Modified Version, together with at least five of the - principal authors of the Document (all of its principal - authors, if it has fewer than five), unless they release you - from this requirement. - - C. State on the Title page the name of the publisher of the - Modified Version, as the publisher. - - D. Preserve all the copyright notices of the Document. - - E. Add an appropriate copyright notice for your modifications - adjacent to the other copyright notices. - - F. Include, immediately after the copyright notices, a license - notice giving the public permission to use the Modified - Version under the terms of this License, in the form shown in - the Addendum below. - - G. Preserve in that license notice the full lists of Invariant - Sections and required Cover Texts given in the Document's - license notice. - - H. Include an unaltered copy of this License. - - I. Preserve the section Entitled "History", Preserve its Title, - and add to it an item stating at least the title, year, new - authors, and publisher of the Modified Version as given on the - Title Page. If there is no section Entitled "History" in the - Document, create one stating the title, year, authors, and - publisher of the Document as given on its Title Page, then add - an item describing the Modified Version as stated in the - previous sentence. - - J. Preserve the network location, if any, given in the Document - for public access to a Transparent copy of the Document, and - likewise the network locations given in the Document for - previous versions it was based on. These may be placed in the - "History" section. You may omit a network location for a work - that was published at least four years before the Document - itself, or if the original publisher of the version it refers - to gives permission. - - K. For any section Entitled "Acknowledgements" or "Dedications", - Preserve the Title of the section, and preserve in the section - all the substance and tone of each of the contributor - acknowledgements and/or dedications given therein. - - L. Preserve all the Invariant Sections of the Document, unaltered - in their text and in their titles. Section numbers or the - equivalent are not considered part of the section titles. - - M. Delete any section Entitled "Endorsements". Such a section - may not be included in the Modified Version. - - N. Do not retitle any existing section to be Entitled - "Endorsements" or to conflict in title with any Invariant - Section. - - O. Preserve any Warranty Disclaimers. - - If the Modified Version includes new front-matter sections or - appendices that qualify as Secondary Sections and contain no - material copied from the Document, you may at your option designate - some or all of these sections as invariant. To do this, add their - titles to the list of Invariant Sections in the Modified Version's - license notice. These titles must be distinct from any other - section titles. - - You may add a section Entitled "Endorsements", provided it contains - nothing but endorsements of your Modified Version by various - parties--for example, statements of peer review or that the text - has been approved by an organization as the authoritative - definition of a standard. - - You may add a passage of up to five words as a Front-Cover Text, - and a passage of up to 25 words as a Back-Cover Text, to the end of - the list of Cover Texts in the Modified Version. Only one passage - of Front-Cover Text and one of Back-Cover Text may be added by (or - through arrangements made by) any one entity. If the Document - already includes a cover text for the same cover, previously added - by you or by arrangement made by the same entity you are acting on - behalf of, you may not add another; but you may replace the old - one, on explicit permission from the previous publisher that added - the old one. - - The author(s) and publisher(s) of the Document do not by this - License give permission to use their names for publicity for or to - assert or imply endorsement of any Modified Version. - - 5. COMBINING DOCUMENTS - - You may combine the Document with other documents released under - this License, under the terms defined in section 4 above for - modified versions, provided that you include in the combination all - of the Invariant Sections of all of the original documents, - unmodified, and list them all as Invariant Sections of your - combined work in its license notice, and that you preserve all - their Warranty Disclaimers. - - The combined work need only contain one copy of this License, and - multiple identical Invariant Sections may be replaced with a single - copy. If there are multiple Invariant Sections with the same name - but different contents, make the title of each such section unique - by adding at the end of it, in parentheses, the name of the - original author or publisher of that section if known, or else a - unique number. Make the same adjustment to the section titles in - the list of Invariant Sections in the license notice of the - combined work. - - In the combination, you must combine any sections Entitled - "History" in the various original documents, forming one section - Entitled "History"; likewise combine any sections Entitled - "Acknowledgements", and any sections Entitled "Dedications". You - must delete all sections Entitled "Endorsements." - - 6. COLLECTIONS OF DOCUMENTS - - You may make a collection consisting of the Document and other - documents released under this License, and replace the individual - copies of this License in the various documents with a single copy - that is included in the collection, provided that you follow the - rules of this License for verbatim copying of each of the documents - in all other respects. - - You may extract a single document from such a collection, and - distribute it individually under this License, provided you insert - a copy of this License into the extracted document, and follow this - License in all other respects regarding verbatim copying of that - document. - - 7. AGGREGATION WITH INDEPENDENT WORKS - - A compilation of the Document or its derivatives with other - separate and independent documents or works, in or on a volume of a - storage or distribution medium, is called an "aggregate" if the - copyright resulting from the compilation is not used to limit the - legal rights of the compilation's users beyond what the individual - works permit. When the Document is included in an aggregate, this - License does not apply to the other works in the aggregate which - are not themselves derivative works of the Document. - - If the Cover Text requirement of section 3 is applicable to these - copies of the Document, then if the Document is less than one half - of the entire aggregate, the Document's Cover Texts may be placed - on covers that bracket the Document within the aggregate, or the - electronic equivalent of covers if the Document is in electronic - form. Otherwise they must appear on printed covers that bracket - the whole aggregate. - - 8. TRANSLATION - - Translation is considered a kind of modification, so you may - distribute translations of the Document under the terms of section - 4. Replacing Invariant Sections with translations requires special - permission from their copyright holders, but you may include - translations of some or all Invariant Sections in addition to the - original versions of these Invariant Sections. You may include a - translation of this License, and all the license notices in the - Document, and any Warranty Disclaimers, provided that you also - include the original English version of this License and the - original versions of those notices and disclaimers. In case of a - disagreement between the translation and the original version of - this License or a notice or disclaimer, the original version will - prevail. - - If a section in the Document is Entitled "Acknowledgements", - "Dedications", or "History", the requirement (section 4) to - Preserve its Title (section 1) will typically require changing the - actual title. - - 9. TERMINATION - - You may not copy, modify, sublicense, or distribute the Document - except as expressly provided under this License. Any attempt - otherwise to copy, modify, sublicense, or distribute it is void, - and will automatically terminate your rights under this License. - - However, if you cease all violation of this License, then your - license from a particular copyright holder is reinstated (a) - provisionally, unless and until the copyright holder explicitly and - finally terminates your license, and (b) permanently, if the - copyright holder fails to notify you of the violation by some - reasonable means prior to 60 days after the cessation. - - Moreover, your license from a particular copyright holder is - reinstated permanently if the copyright holder notifies you of the - violation by some reasonable means, this is the first time you have - received notice of violation of this License (for any work) from - that copyright holder, and you cure the violation prior to 30 days - after your receipt of the notice. - - Termination of your rights under this section does not terminate - the licenses of parties who have received copies or rights from you - under this License. If your rights have been terminated and not - permanently reinstated, receipt of a copy of some or all of the - same material does not give you any rights to use it. - - 10. FUTURE REVISIONS OF THIS LICENSE - - The Free Software Foundation may publish new, revised versions of - the GNU Free Documentation License from time to time. Such new - versions will be similar in spirit to the present version, but may - differ in detail to address new problems or concerns. See - <http://www.gnu.org/copyleft/>. - - Each version of the License is given a distinguishing version - number. If the Document specifies that a particular numbered - version of this License "or any later version" applies to it, you - have the option of following the terms and conditions either of - that specified version or of any later version that has been - published (not as a draft) by the Free Software Foundation. If the - Document does not specify a version number of this License, you may - choose any version ever published (not as a draft) by the Free - Software Foundation. If the Document specifies that a proxy can - decide which future versions of this License can be used, that - proxy's public statement of acceptance of a version permanently - authorizes you to choose that version for the Document. - - 11. RELICENSING - - "Massive Multiauthor Collaboration Site" (or "MMC Site") means any - World Wide Web server that publishes copyrightable works and also - provides prominent facilities for anybody to edit those works. A - public wiki that anybody can edit is an example of such a server. - A "Massive Multiauthor Collaboration" (or "MMC") contained in the - site means any set of copyrightable works thus published on the MMC - site. - - "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0 - license published by Creative Commons Corporation, a not-for-profit - corporation with a principal place of business in San Francisco, - California, as well as future copyleft versions of that license - published by that same organization. - - "Incorporate" means to publish or republish a Document, in whole or - in part, as part of another Document. - - An MMC is "eligible for relicensing" if it is licensed under this - License, and if all works that were first published under this - License somewhere other than this MMC, and subsequently - incorporated in whole or in part into the MMC, (1) had no cover - texts or invariant sections, and (2) were thus incorporated prior - to November 1, 2008. - - The operator of an MMC Site may republish an MMC contained in the - site under CC-BY-SA on the same site at any time before August 1, - 2009, provided the MMC is eligible for relicensing. - -ADDENDUM: How to use this License for your documents -==================================================== - -To use this License in a document you have written, include a copy of -the License in the document and put the following copyright and license -notices just after the title page: - - Copyright (C) YEAR YOUR NAME. - Permission is granted to copy, distribute and/or modify this document - under the terms of the GNU Free Documentation License, Version 1.3 - or any later version published by the Free Software Foundation; - with no Invariant Sections, no Front-Cover Texts, and no Back-Cover - Texts. A copy of the license is included in the section entitled ``GNU - Free Documentation License''. - - If you have Invariant Sections, Front-Cover Texts and Back-Cover -Texts, replace the "with...Texts." line with this: - - with the Invariant Sections being LIST THEIR TITLES, with - the Front-Cover Texts being LIST, and with the Back-Cover Texts - being LIST. - - If you have Invariant Sections without Cover Texts, or some other -combination of the three, merge those two alternatives to suit the -situation. - - If your document contains nontrivial examples of program code, we -recommend releasing these examples in parallel under your choice of free -software license, such as the GNU General Public License, to permit -their use in free software. - - -File: gcj.info, Node: Invoking gcj, Next: Compatibility, Prev: GNU Free Documentation License, Up: Top - -1 Invoking gcj -************** - -As 'gcj' is just another front end to 'gcc', it supports many of the -same options as gcc. *Note Option Summary: (gcc)Option Summary. This -manual only documents the options specific to 'gcj'. - -* Menu: - -* Input and output files:: -* Input Options:: How gcj finds files -* Encodings:: Options controlling source file encoding -* Warnings:: Options controlling warnings specific to gcj -* Linking:: Options for making an executable -* Code Generation:: Options controlling the output of gcj -* Configure-time Options:: Options you won't use - - -File: gcj.info, Node: Input and output files, Next: Input Options, Up: Invoking gcj - -1.1 Input and output files -========================== - -A 'gcj' command is like a 'gcc' command, in that it consists of a number -of options and file names. The following kinds of input file names are -supported: - -'FILE.java' - Java source files. -'FILE.class' - Java bytecode files. -'FILE.zip' -'FILE.jar' - An archive containing one or more '.class' files, all of which are - compiled. The archive may be compressed. Files in an archive - which don't end with '.class' are treated as resource files; they - are compiled into the resulting object file as 'core:' URLs. -'@FILE' - A file containing a whitespace-separated list of input file names. - (Currently, these must all be '.java' source files, but that may - change.) Each named file is compiled, just as if it had been on - the command line. -'LIBRARY.a' -'LIBRARY.so' -'-lLIBNAME' - Libraries to use when linking. See the 'gcc' manual. - - You can specify more than one input file on the 'gcj' command line, -in which case they will all be compiled. If you specify a '-o FILENAME' -option, all the input files will be compiled together, producing a -single output file, named FILENAME. This is allowed even when using -'-S' or '-c', but not when using '-C' or '--resource'. (This is an -extension beyond the what plain 'gcc' allows.) (If more than one input -file is specified, all must currently be '.java' files, though we hope -to fix this.) - - -File: gcj.info, Node: Input Options, Next: Encodings, Prev: Input and output files, Up: Invoking gcj - -1.2 Input Options -================= - -'gcj' has options to control where it looks to find files it needs. For -instance, 'gcj' might need to load a class that is referenced by the -file it has been asked to compile. Like other compilers for the Java -language, 'gcj' has a notion of a "class path". There are several -options and environment variables which can be used to manipulate the -class path. When 'gcj' looks for a given class, it searches the class -path looking for matching '.class' or '.java' file. 'gcj' comes with a -built-in class path which points at the installed 'libgcj.jar', a file -which contains all the standard classes. - - In the text below, a directory or path component can refer either to -an actual directory on the filesystem, or to a '.zip' or '.jar' file, -which 'gcj' will search as if it is a directory. - -'-IDIR' - All directories specified by '-I' are kept in order and prepended - to the class path constructed from all the other options. Unless - compatibility with tools like 'javac' is important, we recommend - always using '-I' instead of the other options for manipulating the - class path. - -'--classpath=PATH' - This sets the class path to PATH, a colon-separated list of paths - (on Windows-based systems, a semicolon-separate list of paths). - This does not override the builtin ("boot") search path. - -'--CLASSPATH=PATH' - Deprecated synonym for '--classpath'. - -'--bootclasspath=PATH' - Where to find the standard builtin classes, such as - 'java.lang.String'. - -'--extdirs=PATH' - For each directory in the PATH, place the contents of that - directory at the end of the class path. - -'CLASSPATH' - This is an environment variable which holds a list of paths. - - The final class path is constructed like so: - - * First come all directories specified via '-I'. - - * If '--classpath' is specified, its value is appended. Otherwise, - if the 'CLASSPATH' environment variable is specified, then its - value is appended. Otherwise, the current directory ('"."') is - appended. - - * If '--bootclasspath' was specified, append its value. Otherwise, - append the built-in system directory, 'libgcj.jar'. - - * Finally, if '--extdirs' was specified, append the contents of the - specified directories at the end of the class path. Otherwise, - append the contents of the built-in extdirs at - '$(prefix)/share/java/ext'. - - The classfile built by 'gcj' for the class 'java.lang.Object' (and -placed in 'libgcj.jar') contains a special zero length attribute -'gnu.gcj.gcj-compiled'. The compiler looks for this attribute when -loading 'java.lang.Object' and will report an error if it isn't found, -unless it compiles to bytecode (the option -'-fforce-classes-archive-check' can be used to override this behavior in -this particular case.) - -'-fforce-classes-archive-check' - This forces the compiler to always check for the special zero - length attribute 'gnu.gcj.gcj-compiled' in 'java.lang.Object' and - issue an error if it isn't found. - -'-fsource=VERSION' - This option is used to choose the source version accepted by 'gcj'. - The default is '1.5'. - - -File: gcj.info, Node: Encodings, Next: Warnings, Prev: Input Options, Up: Invoking gcj - -1.3 Encodings -============= - -The Java programming language uses Unicode throughout. In an effort to -integrate well with other locales, 'gcj' allows '.java' files to be -written using almost any encoding. 'gcj' knows how to convert these -encodings into its internal encoding at compile time. - - You can use the '--encoding=NAME' option to specify an encoding (of a -particular character set) to use for source files. If this is not -specified, the default encoding comes from your current locale. If your -host system has insufficient locale support, then 'gcj' assumes the -default encoding to be the 'UTF-8' encoding of Unicode. - - To implement '--encoding', 'gcj' simply uses the host platform's -'iconv' conversion routine. This means that in practice 'gcj' is -limited by the capabilities of the host platform. - - The names allowed for the argument '--encoding' vary from platform to -platform (since they are not standardized anywhere). However, 'gcj' -implements the encoding named 'UTF-8' internally, so if you choose to -use this for your source files you can be assured that it will work on -every host. - - -File: gcj.info, Node: Warnings, Next: Linking, Prev: Encodings, Up: Invoking gcj - -1.4 Warnings -============ - -'gcj' implements several warnings. As with other generic 'gcc' -warnings, if an option of the form '-Wfoo' enables a warning, then -'-Wno-foo' will disable it. Here we've chosen to document the form of -the warning which will have an effect - the default being the opposite -of what is listed. - -'-Wredundant-modifiers' - With this flag, 'gcj' will warn about redundant modifiers. For - instance, it will warn if an interface method is declared 'public'. - -'-Wextraneous-semicolon' - This causes 'gcj' to warn about empty statements. Empty statements - have been deprecated. - -'-Wno-out-of-date' - This option will cause 'gcj' not to warn when a source file is - newer than its matching class file. By default 'gcj' will warn - about this. - -'-Wno-deprecated' - Warn if a deprecated class, method, or field is referred to. - -'-Wunused' - This is the same as 'gcc''s '-Wunused'. - -'-Wall' - This is the same as '-Wredundant-modifiers -Wextraneous-semicolon - -Wunused'. - - -File: gcj.info, Node: Linking, Next: Code Generation, Prev: Warnings, Up: Invoking gcj - -1.5 Linking -=========== - -To turn a Java application into an executable program, you need to link -it with the needed libraries, just as for C or C++. The linker by -default looks for a global function named 'main'. Since Java does not -have global functions, and a collection of Java classes may have more -than one class with a 'main' method, you need to let the linker know -which of those 'main' methods it should invoke when starting the -application. You can do that in any of these ways: - - * Specify the class containing the desired 'main' method when you - link the application, using the '--main' flag, described below. - * Link the Java package(s) into a shared library (dll) rather than an - executable. Then invoke the application using the 'gij' program, - making sure that 'gij' can find the libraries it needs. - * Link the Java packages(s) with the flag '-lgij', which links in the - 'main' routine from the 'gij' command. This allows you to select - the class whose 'main' method you want to run when you run the - application. You can also use other 'gij' flags, such as '-D' - flags to set properties. Using the '-lgij' library (rather than - the 'gij' program of the previous mechanism) has some advantages: - it is compatible with static linking, and does not require - configuring or installing libraries. - - These 'gij' options relate to linking an executable: - -'--main=CLASSNAME' - This option is used when linking to specify the name of the class - whose 'main' method should be invoked when the resulting executable - is run. - -'-DNAME[=VALUE]' - This option can only be used with '--main'. It defines a system - property named NAME with value VALUE. If VALUE is not specified - then it defaults to the empty string. These system properties are - initialized at the program's startup and can be retrieved at - runtime using the 'java.lang.System.getProperty' method. - -'-lgij' - Create an application whose command-line processing is that of the - 'gij' command. - - This option is an alternative to using '--main'; you cannot use - both. - -'-static-libgcj' - This option causes linking to be done against a static version of - the libgcj runtime library. This option is only available if - corresponding linker support exists. - - *Caution:* Static linking of libgcj may cause essential parts of - libgcj to be omitted. Some parts of libgcj use reflection to load - classes at runtime. Since the linker does not see these references - at link time, it can omit the referred to classes. The result is - usually (but not always) a 'ClassNotFoundException' being thrown at - runtime. Caution must be used when using this option. For more - details see: <http://gcc.gnu.org/wiki/Statically%20linking%20libgcj> - - -File: gcj.info, Node: Code Generation, Next: Configure-time Options, Prev: Linking, Up: Invoking gcj - -1.6 Code Generation -=================== - -In addition to the many 'gcc' options controlling code generation, 'gcj' -has several options specific to itself. - -'-C' - This option is used to tell 'gcj' to generate bytecode ('.class' - files) rather than object code. - -'--resource RESOURCE-NAME' - This option is used to tell 'gcj' to compile the contents of a - given file to object code so it may be accessed at runtime with the - core protocol handler as 'core:/RESOURCE-NAME'. Note that - RESOURCE-NAME is the name of the resource as found at runtime; for - instance, it could be used in a call to 'ResourceBundle.getBundle'. - The actual file name to be compiled this way must be specified - separately. - -'-ftarget=VERSION' - This can be used with '-C' to choose the version of bytecode - emitted by 'gcj'. The default is '1.5'. When not generating - bytecode, this option has no effect. - -'-d DIRECTORY' - When used with '-C', this causes all generated '.class' files to be - put in the appropriate subdirectory of DIRECTORY. By default they - will be put in subdirectories of the current working directory. - -'-fno-bounds-check' - By default, 'gcj' generates code which checks the bounds of all - array indexing operations. With this option, these checks are - omitted, which can improve performance for code that uses arrays - extensively. Note that this can result in unpredictable behavior - if the code in question actually does violate array bounds - constraints. It is safe to use this option if you are sure that - your code will never throw an 'ArrayIndexOutOfBoundsException'. - -'-fno-store-check' - Don't generate array store checks. When storing objects into - arrays, a runtime check is normally generated in order to ensure - that the object is assignment compatible with the component type of - the array (which may not be known at compile-time). With this - option, these checks are omitted. This can improve performance for - code which stores objects into arrays frequently. It is safe to - use this option if you are sure your code will never throw an - 'ArrayStoreException'. - -'-fjni' - With 'gcj' there are two options for writing native methods: CNI - and JNI. By default 'gcj' assumes you are using CNI. If you are - compiling a class with native methods, and these methods are - implemented using JNI, then you must use '-fjni'. This option - causes 'gcj' to generate stubs which will invoke the underlying JNI - methods. - -'-fno-assert' - Don't recognize the 'assert' keyword. This is for compatibility - with older versions of the language specification. - -'-fno-optimize-static-class-initialization' - When the optimization level is greater or equal to '-O2', 'gcj' - will try to optimize the way calls into the runtime are made to - initialize static classes upon their first use (this optimization - isn't carried out if '-C' was specified.) When compiling to native - code, '-fno-optimize-static-class-initialization' will turn this - optimization off, regardless of the optimization level in use. - -'--disable-assertions[=CLASS-OR-PACKAGE]' - Don't include code for checking assertions in the compiled code. - If '=CLASS-OR-PACKAGE' is missing disables assertion code - generation for all classes, unless overridden by a more specific - '--enable-assertions' flag. If CLASS-OR-PACKAGE is a class name, - only disables generating assertion checks within the named class or - its inner classes. If CLASS-OR-PACKAGE is a package name, disables - generating assertion checks within the named package or a - subpackage. - - By default, assertions are enabled when generating class files or - when not optimizing, and disabled when generating optimized - binaries. - -'--enable-assertions[=CLASS-OR-PACKAGE]' - Generates code to check assertions. The option is perhaps - misnamed, as you still need to turn on assertion checking at - run-time, and we don't support any easy way to do that. So this - flag isn't very useful yet, except to partially override - '--disable-assertions'. - -'-findirect-dispatch' - 'gcj' has a special binary compatibility ABI, which is enabled by - the '-findirect-dispatch' option. In this mode, the code generated - by 'gcj' honors the binary compatibility guarantees in the Java - Language Specification, and the resulting object files do not need - to be directly linked against their dependencies. Instead, all - dependencies are looked up at runtime. This allows free mixing of - interpreted and compiled code. - - Note that, at present, '-findirect-dispatch' can only be used when - compiling '.class' files. It will not work when compiling from - source. CNI also does not yet work with the binary compatibility - ABI. These restrictions will be lifted in some future release. - - However, if you compile CNI code with the standard ABI, you can - call it from code built with the binary compatibility ABI. - -'-fbootstrap-classes' - This option can be use to tell 'libgcj' that the compiled classes - should be loaded by the bootstrap loader, not the system class - loader. By default, if you compile a class and link it into an - executable, it will be treated as if it was loaded using the system - class loader. This is convenient, as it means that things like - 'Class.forName()' will search 'CLASSPATH' to find the desired - class. - -'-freduced-reflection' - This option causes the code generated by 'gcj' to contain a reduced - amount of the class meta-data used to support runtime reflection. - The cost of this savings is the loss of the ability to use certain - reflection capabilities of the standard Java runtime environment. - When set all meta-data except for that which is needed to obtain - correct runtime semantics is eliminated. - - For code that does not use reflection (i.e. serialization, RMI, - CORBA or call methods in the 'java.lang.reflect' package), - '-freduced-reflection' will result in proper operation with a - savings in executable code size. - - JNI ('-fjni') and the binary compatibility ABI - ('-findirect-dispatch') do not work properly without full - reflection meta-data. Because of this, it is an error to use these - options with '-freduced-reflection'. - - *Caution:* If there is no reflection meta-data, code that uses a - 'SecurityManager' may not work properly. Also calling - 'Class.forName()' may fail if the calling method has no reflection - meta-data. - - -File: gcj.info, Node: Configure-time Options, Prev: Code Generation, Up: Invoking gcj - -1.7 Configure-time Options -========================== - -Some 'gcj' code generations options affect the resulting ABI, and so can -only be meaningfully given when 'libgcj', the runtime package, is -configured. 'libgcj' puts the appropriate options from this group into -a 'spec' file which is read by 'gcj'. These options are listed here for -completeness; if you are using 'libgcj' then you won't want to touch -these options. - -'-fuse-boehm-gc' - This enables the use of the Boehm GC bitmap marking code. In - particular this causes 'gcj' to put an object marking descriptor - into each vtable. - -'-fhash-synchronization' - By default, synchronization data (the data used for 'synchronize', - 'wait', and 'notify') is pointed to by a word in each object. With - this option 'gcj' assumes that this information is stored in a hash - table and not in the object itself. - -'-fuse-divide-subroutine' - On some systems, a library routine is called to perform integer - division. This is required to get exception handling correct when - dividing by zero. - -'-fcheck-references' - On some systems it's necessary to insert inline checks whenever - accessing an object via a reference. On other systems you won't - need this because null pointer accesses are caught automatically by - the processor. - -'-fuse-atomic-builtins' - On some systems, GCC can generate code for built-in atomic - operations. Use this option to force gcj to use these builtins - when compiling Java code. Where this capability is present it - should be automatically detected, so you won't usually need to use - this option. - - -File: gcj.info, Node: Compatibility, Next: Invoking jcf-dump, Prev: Invoking gcj, Up: Top - -2 Compatibility with the Java Platform -************************************** - -As we believe it is important that the Java platform not be fragmented, -'gcj' and 'libgcj' try to conform to the relevant Java specifications. -However, limited manpower and incomplete and unclear documentation work -against us. So, there are caveats to using 'gcj'. - -* Menu: - -* Limitations:: -* Extensions:: - - -File: gcj.info, Node: Limitations, Next: Extensions, Up: Compatibility - -2.1 Standard features not yet supported -======================================= - -This list of compatibility issues is by no means complete. - - * 'gcj' implements the JDK 1.2 language. It supports inner classes - and the new 1.4 'assert' keyword. It does not yet support the Java - 2 'strictfp' keyword (it recognizes the keyword but ignores it). - - * 'libgcj' is largely compatible with the JDK 1.2 libraries. - However, 'libgcj' is missing many packages, most notably - 'java.awt'. There are also individual missing classes and methods. - We currently do not have a list showing differences between - 'libgcj' and the Java 2 platform. - - * Sometimes the 'libgcj' implementation of a method or class differs - from the JDK implementation. This is not always a bug. Still, if - it affects you, it probably makes sense to report it so that we can - discuss the appropriate response. - - * 'gcj' does not currently allow for piecemeal replacement of - components within 'libgcj'. Unfortunately, programmers often want - to use newer versions of certain packages, such as those provided - by the Apache Software Foundation's Jakarta project. This has - forced us to place the 'org.w3c.dom' and 'org.xml.sax' packages - into their own libraries, separate from 'libgcj'. If you intend to - use these classes, you must link them explicitly with - '-l-org-w3c-dom' and '-l-org-xml-sax'. Future versions of 'gcj' - may not have this restriction. - - -File: gcj.info, Node: Extensions, Prev: Limitations, Up: Compatibility - -2.2 Extra features unique to gcj -================================ - -The main feature of 'gcj' is that it can compile programs written in the -Java programming language to native code. Most extensions that have -been added are to facilitate this functionality. - - * 'gcj' makes it easy and efficient to mix code written in Java and - C++. *Note About CNI::, for more info on how to use this in your - programs. - - * When you compile your classes into a shared library using - '-findirect-dispatch' then add them to the system-wide classmap.db - file using 'gcj-dbtool', they will be automatically loaded by the - 'libgcj' system classloader. This is the new, preferred - classname-to-library resolution mechanism. *Note Invoking - gcj-dbtool::, for more information on using the classmap database. - - * The old classname-to-library lookup mechanism is still supported - through the 'gnu.gcj.runtime.VMClassLoader.library_control' - property, but it is deprecated and will likely be removed in some - future release. When trying to load a class 'gnu.pkg.SomeClass' - the system classloader will first try to load the shared library - 'lib-gnu-pkg-SomeClass.so', if that fails to load the class then it - will try to load 'lib-gnu-pkg.so' and finally when the class is - still not loaded it will try to load 'lib-gnu.so'. Note that all - '.'s will be transformed into '-'s and that searching for inner - classes starts with their outermost outer class. If the class - cannot be found this way the system classloader tries to use the - 'libgcj' bytecode interpreter to load the class from the standard - classpath. This process can be controlled to some degree via the - 'gnu.gcj.runtime.VMClassLoader.library_control' property; *Note - libgcj Runtime Properties::. - - * 'libgcj' includes a special 'gcjlib' URL type. A URL of this form - is like a 'jar' URL, and looks like - 'gcjlib:/path/to/shared/library.so!/path/to/resource'. An access - to one of these URLs causes the shared library to be 'dlopen()'d, - and then the resource is looked for in that library. These URLs - are most useful when used in conjunction with - 'java.net.URLClassLoader'. Note that, due to implementation - limitations, currently any such URL can be accessed by only one - class loader, and libraries are never unloaded. This means some - care must be exercised to make sure that a 'gcjlib' URL is not - accessed by more than one class loader at once. In a future - release this limitation will be lifted, and such libraries will be - mapped privately. - - * A program compiled by 'gcj' will examine the 'GCJ_PROPERTIES' - environment variable and change its behavior in some ways. In - particular 'GCJ_PROPERTIES' holds a list of assignments to global - properties, such as would be set with the '-D' option to 'java'. - For instance, 'java.compiler=gcj' is a valid (but currently - meaningless) setting. - - -File: gcj.info, Node: Invoking jcf-dump, Next: Invoking gij, Prev: Compatibility, Up: Top - -3 Invoking jcf-dump -******************* - -This is a class file examiner, similar to 'javap'. It will print -information about a number of classes, which are specified by class name -or file name. - -'-c' - Disassemble method bodies. By default method bodies are not - printed. - -'--print-constants' - Print the constant pool. When printing a reference to a constant - also print its index in the constant pool. - -'--javap' - Generate output in 'javap' format. The implementation of this - feature is very incomplete. - -'--classpath=PATH' -'--CLASSPATH=PATH' -'-IDIRECTORY' -'-o FILE' - These options as the same as the corresponding 'gcj' options. - -'--help' - Print help, then exit. - -'--version' - Print version number, then exit. - -'-v, --verbose' - Print extra information while running. Implies - '--print-constants'. - - -File: gcj.info, Node: Invoking gij, Next: Invoking gcj-dbtool, Prev: Invoking jcf-dump, Up: Top - -4 Invoking gij -************** - -'gij' is a Java bytecode interpreter included with 'libgcj'. 'gij' is -not available on every platform; porting it requires a small amount of -assembly programming which has not been done for all the targets -supported by 'gcj'. - - The primary argument to 'gij' is the name of a class or, with '-jar', -a jar file. Options before this argument are interpreted by 'gij'; -remaining options are passed to the interpreted program. - - If a class name is specified and this class does not have a 'main' -method with the appropriate signature (a 'static void' method with a -'String[]' as its sole argument), then 'gij' will print an error and -exit. - - If a jar file is specified then 'gij' will use information in it to -determine which class' 'main' method will be invoked. - - 'gij' will invoke the 'main' method with all the remaining -command-line options. - - Note that 'gij' is not limited to interpreting code. Because -'libgcj' includes a class loader which can dynamically load shared -objects, it is possible to give 'gij' the name of a class which has been -compiled and put into a shared library on the class path. - -'-cp PATH' -'-classpath PATH' - Set the initial class path. The class path is used for finding - class and resource files. If specified, this option overrides the - 'CLASSPATH' environment variable. Note that this option is ignored - if '-jar' is used. - -'-DNAME[=VALUE]' - This defines a system property named NAME with value VALUE. If - VALUE is not specified then it defaults to the empty string. These - system properties are initialized at the program's startup and can - be retrieved at runtime using the 'java.lang.System.getProperty' - method. - -'-ms=NUMBER' - Equivalent to '-Xms'. - -'-mx=NUMBER' - Equivalent to '-Xmx'. - -'-noverify' - Do not verify compliance of bytecode with the VM specification. In - addition, this option disables type verification which is otherwise - performed on BC-ABI compiled code. - -'-X' -'-XARGUMENT' - Supplying '-X' by itself will cause 'gij' to list all the supported - '-X' options. Currently these options are supported: - - '-XmsSIZE' - Set the initial heap size. - - '-XmxSIZE' - Set the maximum heap size. - - '-XssSIZE' - Set the thread stack size. - - Unrecognized '-X' options are ignored, for compatibility with other - runtimes. - -'-jar' - This indicates that the name passed to 'gij' should be interpreted - as the name of a jar file, not a class. - -'--help' -'-?' - Print help, then exit. - -'--showversion' - Print version number and continue. - -'--fullversion' - Print detailed version information, then exit. - -'--version' - Print version number, then exit. - -'-verbose' -'-verbose:class' - Each time a class is initialized, print a short message on standard - error. - - 'gij' also recognizes and ignores the following options, for -compatibility with existing application launch scripts: '-client', -'-server', '-hotspot', '-jrockit', '-agentlib', '-agentpath', '-debug', -'-d32', '-d64', '-javaagent', '-noclassgc', '-verify', and -'-verifyremote'. - - -File: gcj.info, Node: Invoking gcj-dbtool, Next: Invoking jv-convert, Prev: Invoking gij, Up: Top - -5 Invoking gcj-dbtool. -********************** - -'gcj-dbtool' is a tool for creating and manipulating class file mapping -databases. 'libgcj' can use these databases to find a shared library -corresponding to the bytecode representation of a class. This -functionality is useful for ahead-of-time compilation of a program that -has no knowledge of 'gcj'. - - 'gcj-dbtool' works best if all the jar files added to it are compiled -using '-findirect-dispatch'. - - Note that 'gcj-dbtool' is currently available as "preview -technology". We believe it is a reasonable way to allow -application-transparent ahead-of-time compilation, but this is an -unexplored area. We welcome your comments. - -'-n DBFILE [SIZE]' - This creates a new database. Currently, databases cannot be - resized; you can choose a larger initial size if desired. The - default size is 32,749. - -'-a DBFILE JARFILE LIB' -'-f DBFILE JARFILE LIB' - This adds a jar file to the database. For each class file in the - jar, a cryptographic signature of the bytecode representation of - the class is recorded in the database. At runtime, a class is - looked up by its signature and the compiled form of the class is - looked for in the corresponding shared library. The '-a' option - will verify that LIB exists before adding it to the database; '-f' - skips this check. - -'[-][-0] -m DBFILE DBFILE,[DBFILE]' - Merge a number of databases. The output database overwrites any - existing database. To add databases into an existing database, - include the destination in the list of sources. - - If '-' or '-0' are used, the list of files to read is taken from - standard input instead of the command line. For '-0', Input - filenames are terminated by a null character instead of by - whitespace. Useful when arguments might contain white space. The - GNU find -print0 option produces input suitable for this mode. - -'-t DBFILE' - Test a database. - -'-l DBFILE' - List the contents of a database. - -'-p' - Print the name of the default database. If there is no default - database, this prints a blank line. If LIBDIR is specified, use it - instead of the default library directory component of the database - name. - -'--help' - Print a help message, then exit. - -'--version' -'-v' - Print version information, then exit. - - -File: gcj.info, Node: Invoking jv-convert, Next: Invoking grmic, Prev: Invoking gcj-dbtool, Up: Top - -6 Invoking jv-convert -********************* - -'jv-convert' ['OPTION'] ... [INPUTFILE [OUTPUTFILE]] - - 'jv-convert' is a utility included with 'libgcj' which converts a -file from one encoding to another. It is similar to the Unix 'iconv' -utility. - - The encodings supported by 'jv-convert' are platform-dependent. -Currently there is no way to get a list of all supported encodings. - -'--encoding NAME' -'--from NAME' - Use NAME as the input encoding. The default is the current - locale's encoding. - -'--to NAME' - Use NAME as the output encoding. The default is the 'JavaSrc' - encoding; this is ASCII with '\u' escapes for non-ASCII characters. - -'-i FILE' - Read from FILE. The default is to read from standard input. - -'-o FILE' - Write to FILE. The default is to write to standard output. - -'--reverse' - Swap the input and output encodings. - -'--help' - Print a help message, then exit. - -'--version' - Print version information, then exit. - - -File: gcj.info, Node: Invoking grmic, Next: Invoking gc-analyze, Prev: Invoking jv-convert, Up: Top - -7 Invoking grmic -**************** - -'grmic' ['OPTION'] ... CLASS ... - - 'grmic' is a utility included with 'libgcj' which generates stubs for -remote objects. - - Note that this program isn't yet fully compatible with the JDK -'grmic'. Some options, such as '-classpath', are recognized but -currently ignored. We have left these options undocumented for now. - - Long options can also be given with a GNU-style leading '--'. For -instance, '--help' is accepted. - -'-keep' -'-keepgenerated' - By default, 'grmic' deletes intermediate files. Either of these - options causes it not to delete such files. - -'-v1.1' - Cause 'grmic' to create stubs and skeletons for the 1.1 protocol - version. - -'-vcompat' - Cause 'grmic' to create stubs and skeletons compatible with both - the 1.1 and 1.2 protocol versions. This is the default. - -'-v1.2' - Cause 'grmic' to create stubs and skeletons for the 1.2 protocol - version. - -'-nocompile' - Don't compile the generated files. - -'-verbose' - Print information about what 'grmic' is doing. - -'-d DIRECTORY' - Put output files in DIRECTORY. By default the files are put in the - current working directory. - -'-help' - Print a help message, then exit. - -'-version' - Print version information, then exit. - - -File: gcj.info, Node: Invoking gc-analyze, Next: Invoking aot-compile, Prev: Invoking grmic, Up: Top - -8 Invoking gc-analyze -********************* - -'gc-analyze' ['OPTION'] ... [FILE] - - 'gc-analyze' prints an analysis of a GC memory dump to standard out. - - The memory dumps may be created by calling -'gnu.gcj.util.GCInfo.enumerate(String namePrefix)' from java code. A -memory dump will be created on an out of memory condition if -'gnu.gcj.util.GCInfo.setOOMDump(String namePrefix)' is called before the -out of memory occurs. - - Running this program will create two files: 'TestDump001' and -'TestDump001.bytes'. - - import gnu.gcj.util.*; - import java.util.*; - - public class GCDumpTest - { - static public void main(String args[]) - { - ArrayList<String> l = new ArrayList<String>(1000); - - for (int i = 1; i < 1500; i++) { - l.add("This is string #" + i); - } - GCInfo.enumerate("TestDump"); - } - } - - The memory dump may then be displayed by running: - - gc-analyze -v TestDump001 - -'--verbose' -'-v' - Verbose output. - -'-p TOOL-PREFIX' - Prefix added to the names of the 'nm' and 'readelf' commands. - -'-d DIRECTORY' - Directory that contains the executable and shared libraries used - when the dump was generated. - -'--help' - Print a help message, then exit. - -'--version' - Print version information, then exit. - - -File: gcj.info, Node: Invoking aot-compile, Next: Invoking rebuild-gcj-db, Prev: Invoking gc-analyze, Up: Top - -9 Invoking aot-compile -********************** - -'aot-compile' is a script that searches a directory for Java bytecode -(as class files, or in jars) and uses 'gcj' to compile it to native code -and generate the databases from it. - -'-M, --make=PATH' - Specify the path to the 'make' executable to use. - -'-C, --gcj=PATH' - Specify the path to the 'gcj' executable to use. - -'-D, --dbtool=PATH' - Specify the path to the 'gcj-dbtool' executable to use. - -'-m, --makeflags=FLAGS' - Specify flags to pass to 'make' during the build. - -'-c, --gcjflags=FLAGS' - Specify flags to pass to 'gcj' during compilation, in addition to - '-fPIC -findirect-dispatch -fjni'. - -'-l, --ldflags=FLAGS' - Specify flags to pass to 'gcj' during linking, in addition to - '-Wl,-Bsymbolic'. - -'-e, --exclude=PATH' - Do not compile PATH. - - -File: gcj.info, Node: Invoking rebuild-gcj-db, Next: About CNI, Prev: Invoking aot-compile, Up: Top - -10 Invoking rebuild-gcj-db -************************** - -'rebuild-gcj-db' is a script that merges the per-solib databases made by -'aot-compile' into one system-wide database so 'gij' can find the -solibs. - - -File: gcj.info, Node: About CNI, Next: System properties, Prev: Invoking rebuild-gcj-db, Up: Top - -11 About CNI -************ - -This documents CNI, the Compiled Native Interface, which is is a -convenient way to write Java native methods using C++. This is a more -efficient, more convenient, but less portable alternative to the -standard JNI (Java Native Interface). - -* Menu: - -* Basic concepts:: Introduction to using CNI. -* Packages:: How packages are mapped to C++. -* Primitive types:: Handling primitive Java types in C++. -* Reference types:: Handling Java reference types in C++. -* Interfaces:: How Java interfaces map to C++. -* Objects and Classes:: C++ and Java classes. -* Class Initialization:: How objects are initialized. -* Object allocation:: How to create Java objects in C++. -* Memory allocation:: How to allocate and free memory. -* Arrays:: Dealing with Java arrays in C++. -* Methods:: Java methods in C++. -* Strings:: Information about Java Strings. -* Mixing with C++:: How CNI can interoperate with C++. -* Exception Handling:: How exceptions are handled. -* Synchronization:: Synchronizing between Java and C++. -* Invocation:: Starting the Java runtime from C++. -* Reflection:: Using reflection from C++. - - -File: gcj.info, Node: Basic concepts, Next: Packages, Up: About CNI - -11.1 Basic concepts -=================== - -In terms of languages features, Java is mostly a subset of C++. Java -has a few important extensions, plus a powerful standard class library, -but on the whole that does not change the basic similarity. Java is a -hybrid object-oriented language, with a few native types, in addition to -class types. It is class-based, where a class may have static as well -as per-object fields, and static as well as instance methods. -Non-static methods may be virtual, and may be overloaded. Overloading -is resolved at compile time by matching the actual argument types -against the parameter types. Virtual methods are implemented using -indirect calls through a dispatch table (virtual function table). -Objects are allocated on the heap, and initialized using a constructor -method. Classes are organized in a package hierarchy. - - All of the listed attributes are also true of C++, though C++ has -extra features (for example in C++ objects may be allocated not just on -the heap, but also statically or in a local stack frame). Because 'gcj' -uses the same compiler technology as G++ (the GNU C++ compiler), it is -possible to make the intersection of the two languages use the same ABI -(object representation and calling conventions). The key idea in CNI is -that Java objects are C++ objects, and all Java classes are C++ classes -(but not the other way around). So the most important task in -integrating Java and C++ is to remove gratuitous incompatibilities. - - You write CNI code as a regular C++ source file. (You do have to use -a Java/CNI-aware C++ compiler, specifically a recent version of G++.) - -A CNI C++ source file must have: - - #include <gcj/cni.h> - -and then must include one header file for each Java class it uses, e.g.: - - #include <java/lang/Character.h> - #include <java/util/Date.h> - #include <java/lang/IndexOutOfBoundsException.h> - -These header files are automatically generated by 'gcjh'. - - CNI provides some functions and macros to make using Java objects and -primitive types from C++ easier. In general, these CNI functions and -macros start with the 'Jv' prefix, for example the function -'JvNewObjectArray'. This convention is used to avoid conflicts with -other libraries. Internal functions in CNI start with the prefix -'_Jv_'. You should not call these; if you find a need to, let us know -and we will try to come up with an alternate solution. - -11.1.1 Limitations ------------------- - -Whilst a Java class is just a C++ class that doesn't mean that you are -freed from the shackles of Java, a CNI C++ class must adhere to the -rules of the Java programming language. - - For example: it is not possible to declare a method in a CNI class -that will take a C string ('char*') as an argument, or to declare a -member variable of some non-Java datatype. - - -File: gcj.info, Node: Packages, Next: Primitive types, Prev: Basic concepts, Up: About CNI - -11.2 Packages -============= - -The only global names in Java are class names, and packages. A -"package" can contain zero or more classes, and also zero or more -sub-packages. Every class belongs to either an unnamed package or a -package that has a hierarchical and globally unique name. - - A Java package is mapped to a C++ "namespace". The Java class -'java.lang.String' is in the package 'java.lang', which is a sub-package -of 'java'. The C++ equivalent is the class 'java::lang::String', which -is in the namespace 'java::lang' which is in the namespace 'java'. - -Here is how you could express this: - - (// Declare the class(es), possibly in a header file: - namespace java { - namespace lang { - class Object; - class String; - ... - } - } - - class java::lang::String : public java::lang::Object - { - ... - }; - -The 'gcjh' tool automatically generates the necessary namespace -declarations. - -11.2.1 Leaving out package names --------------------------------- - -Always using the fully-qualified name of a java class can be tiresomely -verbose. Using the full qualified name also ties the code to a single -package making code changes necessary should the class move from one -package to another. The Java 'package' declaration specifies that the -following class declarations are in the named package, without having to -explicitly name the full package qualifiers. The 'package' declaration -can be followed by zero or more 'import' declarations, which allows -either a single class or all the classes in a package to be named by a -simple identifier. C++ provides something similar with the 'using' -declaration and directive. - -In Java: - - import PACKAGE-NAME.CLASS-NAME; - -allows the program text to refer to CLASS-NAME as a shorthand for the -fully qualified name: 'PACKAGE-NAME.CLASS-NAME'. - -To achieve the same effect C++, you have to do this: - - using PACKAGE-NAME::CLASS-NAME; - -Java can also cause imports on demand, like this: - - import PACKAGE-NAME.*; - -Doing this allows any class from the package PACKAGE-NAME to be referred -to only by its class-name within the program text. - -The same effect can be achieved in C++ like this: - - using namespace PACKAGE-NAME; - - -File: gcj.info, Node: Primitive types, Next: Reference types, Prev: Packages, Up: About CNI - -11.3 Primitive types -==================== - -Java provides 8 "primitives" types which represent integers, floats, -characters and booleans (and also the void type). C++ has its own very -similar concrete types. Such types in C++ however are not always -implemented in the same way (an int might be 16, 32 or 64 bits for -example) so CNI provides a special C++ type for each primitive Java -type: - -*Java type* *C/C++ typename* *Description* -'char' 'jchar' 16 bit Unicode character -'boolean' 'jboolean' logical (true or false) values -'byte' 'jbyte' 8-bit signed integer -'short' 'jshort' 16 bit signed integer -'int' 'jint' 32 bit signed integer -'long' 'jlong' 64 bit signed integer -'float' 'jfloat' 32 bit IEEE floating point number -'double' 'jdouble' 64 bit IEEE floating point number -'void' 'void' no value - - When referring to a Java type You should always use these C++ -typenames (e.g.: 'jint') to avoid disappointment. - -11.3.1 Reference types associated with primitive types ------------------------------------------------------- - -In Java each primitive type has an associated reference type, e.g.: -'boolean' has an associated 'java.lang.Boolean.TYPE' class. In order to -make working with such classes easier GCJ provides the macro -'JvPrimClass': - - -- macro: JvPrimClass type - Return a pointer to the 'Class' object corresponding to the type - supplied. - - JvPrimClass(void) => java.lang.Void.TYPE - - -File: gcj.info, Node: Reference types, Next: Interfaces, Prev: Primitive types, Up: About CNI - -11.4 Reference types -==================== - -A Java reference type is treated as a class in C++. Classes and -interfaces are handled this way. A Java reference is translated to a -C++ pointer, so for instance a Java 'java.lang.String' becomes, in C++, -'java::lang::String *'. - - CNI provides a few built-in typedefs for the most common classes: -*Java type* *C++ typename* *Description* -'java.lang.Object' 'jobject' Object type -'java.lang.String' 'jstring' String type -'java.lang.Class' 'jclass' Class type - - Every Java class or interface has a corresponding 'Class' instance. -These can be accessed in CNI via the static 'class$' field of a class. -The 'class$' field is of type 'Class' (and not 'Class *'), so you will -typically take the address of it. - - Here is how you can refer to the class of 'String', which in Java -would be written 'String.class': - - using namespace java::lang; - doSomething (&String::class$); - - -File: gcj.info, Node: Interfaces, Next: Objects and Classes, Prev: Reference types, Up: About CNI - -11.5 Interfaces -=============== - -A Java class can "implement" zero or more "interfaces", in addition to -inheriting from a single base class. - - CNI allows CNI code to implement methods of interfaces. You can also -call methods through interface references, with some limitations. - - CNI doesn't understand interface inheritance at all yet. So, you can -only call an interface method when the declared type of the field being -called matches the interface which declares that method. The workaround -is to cast the interface reference to the right superinterface. - - For example if you have: - - interface A - { - void a(); - } - - interface B extends A - { - void b(); - } - - and declare a variable of type 'B' in C++, you can't call 'a()' -unless you cast it to an 'A' first. - - -File: gcj.info, Node: Objects and Classes, Next: Class Initialization, Prev: Interfaces, Up: About CNI - -11.6 Objects and Classes -======================== - -11.6.1 Classes --------------- - -All Java classes are derived from 'java.lang.Object'. C++ does not have -a unique root class, but we use the C++ class 'java::lang::Object' as -the C++ version of the 'java.lang.Object' Java class. All other Java -classes are mapped into corresponding C++ classes derived from -'java::lang::Object'. - - Interface inheritance (the 'implements' keyword) is currently not -reflected in the C++ mapping. - -11.6.2 Object fields --------------------- - -Each object contains an object header, followed by the instance fields -of the class, in order. The object header consists of a single pointer -to a dispatch or virtual function table. (There may be extra fields _in -front of_ the object, for example for memory management, but this is -invisible to the application, and the reference to the object points to -the dispatch table pointer.) - - The fields are laid out in the same order, alignment, and size as in -C++. Specifically, 8-bit and 16-bit native types ('byte', 'short', -'char', and 'boolean') are _not_ widened to 32 bits. Note that the Java -VM does extend 8-bit and 16-bit types to 32 bits when on the VM stack or -temporary registers. - - If you include the 'gcjh'-generated header for a class, you can -access fields of Java classes in the _natural_ way. For example, given -the following Java class: - - public class Int - { - public int i; - public Int (int i) { this.i = i; } - public static Int zero = new Int(0); - } - - you can write: - - #include <gcj/cni.h>; - #include <Int>; - - Int* - mult (Int *p, jint k) - { - if (k == 0) - return Int::zero; // Static member access. - return new Int(p->i * k); - } - -11.6.3 Access specifiers ------------------------- - -CNI does not strictly enforce the Java access specifiers, because Java -permissions cannot be directly mapped into C++ permission. Private Java -fields and methods are mapped to private C++ fields and methods, but -other fields and methods are mapped to public fields and methods. - - -File: gcj.info, Node: Class Initialization, Next: Object allocation, Prev: Objects and Classes, Up: About CNI - -11.7 Class Initialization -========================= - -Java requires that each class be automatically initialized at the time -of the first active use. Initializing a class involves initializing the -static fields, running code in class initializer methods, and -initializing base classes. There may also be some implementation -specific actions, such as allocating 'String' objects corresponding to -string literals in the code. - - The GCJ compiler inserts calls to 'JvInitClass' at appropriate places -to ensure that a class is initialized when required. The C++ compiler -does not insert these calls automatically--it is the programmer's -responsibility to make sure classes are initialized. However, this is -fairly painless because of the conventions assumed by the Java system. - - First, 'libgcj' will make sure a class is initialized before an -instance of that object is created. This is one of the responsibilities -of the 'new' operation. This is taken care of both in Java code, and in -C++ code. When G++ sees a 'new' of a Java class, it will call a routine -in 'libgcj' to allocate the object, and that routine will take care of -initializing the class. Note however that this does not happen for Java -arrays; you must allocate those using the appropriate CNI function. It -follows that you can access an instance field, or call an instance -(non-static) method and be safe in the knowledge that the class and all -of its base classes have been initialized. - - Invoking a static method is also safe. This is because the Java -compiler adds code to the start of a static method to make sure the -class is initialized. However, the C++ compiler does not add this extra -code. Hence, if you write a native static method using CNI, you are -responsible for calling 'JvInitClass' before doing anything else in the -method (unless you are sure it is safe to leave it out). - - Accessing a static field also requires the class of the field to be -initialized. The Java compiler will generate code to call 'JvInitClass' -before getting or setting the field. However, the C++ compiler will not -generate this extra code, so it is your responsibility to make sure the -class is initialized before you access a static field from C++. - - -File: gcj.info, Node: Object allocation, Next: Memory allocation, Prev: Class Initialization, Up: About CNI - -11.8 Object allocation -====================== - -New Java objects are allocated using a "class instance creation -expression", e.g.: - - new TYPE ( ... ) - - The same syntax is used in C++. The main difference is that C++ -objects have to be explicitly deleted; in Java they are automatically -deleted by the garbage collector. Using CNI, you can allocate a new -Java object using standard C++ syntax and the C++ compiler will allocate -memory from the garbage collector. If you have overloaded constructors, -the compiler will choose the correct one using standard C++ overload -resolution rules. - -For example: - - java::util::Hashtable *ht = new java::util::Hashtable(120); - - -File: gcj.info, Node: Memory allocation, Next: Arrays, Prev: Object allocation, Up: About CNI - -11.9 Memory allocation -====================== - -When allocating memory in CNI methods it is best to handle out-of-memory -conditions by throwing a Java exception. These functions are provided -for that purpose: - - -- Function: void* JvMalloc (jsize SIZE) - Calls malloc. Throws 'java.lang.OutOfMemoryError' if allocation - fails. - - -- Function: void* JvRealloc (void* PTR, jsize SIZE) - Calls realloc. Throws 'java.lang.OutOfMemoryError' if reallocation - fails. - - -- Function: void JvFree (void* PTR) - Calls free. - - -File: gcj.info, Node: Arrays, Next: Methods, Prev: Memory allocation, Up: About CNI - -11.10 Arrays -============ - -While in many ways Java is similar to C and C++, it is quite different -in its treatment of arrays. C arrays are based on the idea of pointer -arithmetic, which would be incompatible with Java's security -requirements. Java arrays are true objects (array types inherit from -'java.lang.Object'). An array-valued variable is one that contains a -reference (pointer) to an array object. - - Referencing a Java array in C++ code is done using the 'JArray' -template, which as defined as follows: - - class __JArray : public java::lang::Object - { - public: - int length; - }; - - template<class T> - class JArray : public __JArray - { - T data[0]; - public: - T& operator[](jint i) { return data[i]; } - }; - - There are a number of 'typedef's which correspond to 'typedef's from -the JNI. Each is the type of an array holding objects of the relevant -type: - - typedef __JArray *jarray; - typedef JArray<jobject> *jobjectArray; - typedef JArray<jboolean> *jbooleanArray; - typedef JArray<jbyte> *jbyteArray; - typedef JArray<jchar> *jcharArray; - typedef JArray<jshort> *jshortArray; - typedef JArray<jint> *jintArray; - typedef JArray<jlong> *jlongArray; - typedef JArray<jfloat> *jfloatArray; - typedef JArray<jdouble> *jdoubleArray; - - -- Method on template<class T>: T* elements (JArray<T> ARRAY) - This template function can be used to get a pointer to the elements - of the 'array'. For instance, you can fetch a pointer to the - integers that make up an 'int[]' like so: - - extern jintArray foo; - jint *intp = elements (foo); - - The name of this function may change in the future. - - -- Function: jobjectArray JvNewObjectArray (jsize LENGTH, jclass KLASS, - jobject INIT) - This creates a new array whose elements have reference type. - 'klass' is the type of elements of the array and 'init' is the - initial value put into every slot in the array. - - using namespace java::lang; - JArray<String *> *array - = (JArray<String *> *) JvNewObjectArray(length, &String::class$, NULL); - -11.10.1 Creating arrays ------------------------ - -For each primitive type there is a function which can be used to create -a new array of that type. The name of the function is of the form: - - JvNewTYPEArray - -For example: - - JvNewBooleanArray - -can be used to create an array of Java primitive boolean types. - -The following function definition is the template for all such -functions: - - -- Function: jbooleanArray JvNewBooleanArray (jint LENGTH) - Creates an array LENGTH indices long. - - -- Function: jsize JvGetArrayLength (jarray ARRAY) - Returns the length of the ARRAY. - - -File: gcj.info, Node: Methods, Next: Strings, Prev: Arrays, Up: About CNI - -11.11 Methods -============= - -Java methods are mapped directly into C++ methods. The header files -generated by 'gcjh' include the appropriate method definitions. -Basically, the generated methods have the same names and _corresponding_ -types as the Java methods, and are called in the natural manner. - -11.11.1 Overloading -------------------- - -Both Java and C++ provide method overloading, where multiple methods in -a class have the same name, and the correct one is chosen (at compile -time) depending on the argument types. The rules for choosing the -correct method are (as expected) more complicated in C++ than in Java, -but given a set of overloaded methods generated by 'gcjh' the C++ -compiler will choose the expected one. - - Common assemblers and linkers are not aware of C++ overloading, so -the standard implementation strategy is to encode the parameter types of -a method into its assembly-level name. This encoding is called -"mangling", and the encoded name is the "mangled name". The same -mechanism is used to implement Java overloading. For C++/Java -interoperability, it is important that both the Java and C++ compilers -use the _same_ encoding scheme. - -11.11.2 Static methods ----------------------- - -Static Java methods are invoked in CNI using the standard C++ syntax, -using the '::' operator rather than the '.' operator. - -For example: - - jint i = java::lang::Math::round((jfloat) 2.3); - -C++ method definition syntax is used to define a static native method. -For example: - - #include <java/lang/Integer> - java::lang::Integer* - java::lang::Integer::getInteger(jstring str) - { - ... - } - -11.11.3 Object Constructors ---------------------------- - -Constructors are called implicitly as part of object allocation using -the 'new' operator. - -For example: - - java::lang::Integer *x = new java::lang::Integer(234); - - Java does not allow a constructor to be a native method. This -limitation can be coded round however because a constructor can _call_ a -native method. - -11.11.4 Instance methods ------------------------- - -Calling a Java instance method from a C++ CNI method is done using the -standard C++ syntax, e.g.: - - // First create the Java object. - java::lang::Integer *x = new java::lang::Integer(234); - // Now call a method. - jint prim_value = x->intValue(); - if (x->longValue == 0) - ... - -Defining a Java native instance method is also done the natural way: - - #include <java/lang/Integer.h> - - jdouble - java::lang:Integer::doubleValue() - { - return (jdouble) value; - } - -11.11.5 Interface methods -------------------------- - -In Java you can call a method using an interface reference. This is -supported, but not completely. *Note Interfaces::. - - -File: gcj.info, Node: Strings, Next: Mixing with C++, Prev: Methods, Up: About CNI - -11.12 Strings -============= - -CNI provides a number of utility functions for working with Java Java -'String' objects. The names and interfaces are analogous to those of -JNI. - - -- Function: jstring JvNewString (const jchar* CHARS, jsize LEN) - Returns a Java 'String' object with characters from the array of - Unicode characters CHARS up to the index LEN in that array. - - -- Function: jstring JvNewStringLatin1 (const char* BYTES, jsize LEN) - Returns a Java 'String' made up of LEN bytes from BYTES. - - -- Function: jstring JvNewStringLatin1 (const char* BYTES) - As above but the length of the 'String' is 'strlen(BYTES)'. - - -- Function: jstring JvNewStringUTF (const char* BYTES) - Returns a 'String' which is made up of the UTF encoded characters - present in the C string BYTES. - - -- Function: jchar* JvGetStringChars (jstring STR) - Returns a pointer to an array of characters making up the 'String' - STR. - - -- Function: int JvGetStringUTFLength (jstring STR) - Returns the number of bytes required to encode the contents of the - 'String' STR in UTF-8. - - -- Function: jsize JvGetStringUTFRegion (jstring STR, jsize START, - jsize LEN, char* BUF) - Puts the UTF-8 encoding of a region of the 'String' STR into the - buffer 'buf'. The region to fetch is marked by START and LEN. - - Note that BUF is a buffer, not a C string. It is _not_ null - terminated. - - -File: gcj.info, Node: Mixing with C++, Next: Exception Handling, Prev: Strings, Up: About CNI - -11.13 Interoperating with C/C++ -=============================== - -Because CNI is designed to represent Java classes and methods it cannot -be mixed readily with C/C++ types. - - One important restriction is that Java classes cannot have non-Java -type instance or static variables and cannot have methods which take -non-Java types as arguments or return non-Java types. - -None of the following is possible with CNI: - - - class ::MyClass : public java::lang::Object - { - char* variable; // char* is not a valid Java type. - } - - - uint - ::SomeClass::someMethod (char *arg) - { - . - . - . - } // 'uint' is not a valid Java type, neither is 'char*' - -Of course, it is ok to use C/C++ types within the scope of a method: - - jint - ::SomeClass::otherMethod (jstring str) - { - char *arg = ... - . - . - . - } - -11.13.1 RawData ---------------- - -The above restriction can be problematic, so CNI includes the -'gnu.gcj.RawData' class. The 'RawData' class is a "non-scanned -reference" type. In other words variables declared of type 'RawData' -can contain any data and are not checked by the compiler or memory -manager in any way. - - This means that you can put C/C++ data structures (including classes) -in your CNI classes, as long as you use the appropriate cast. - -Here are some examples: - - - class ::MyClass : public java::lang::Object - { - gnu.gcj.RawData string; - - MyClass (); - gnu.gcj.RawData getText (); - void printText (); - } - - ::MyClass::MyClass () - { - char* text = ... - string = text; - } - - gnu.gcj.RawData - ::MyClass::getText () - { - return string; - } - - void - ::MyClass::printText () - { - printf("%s\n", (char*) string); - } - -11.13.2 RawDataManaged ----------------------- - -'gnu.gcj.RawDataManaged' is another type used to indicate special data -used by native code. Unlike the 'RawData' type, fields declared as -'RawDataManaged' will be "marked" by the memory manager and considered -for garbage collection. - - Native data which is allocated using CNI's 'JvAllocBytes()' function -and stored in a 'RawDataManaged' will be automatically freed when the -Java object it is associated with becomes unreachable. - -11.13.3 Native memory allocation --------------------------------- - - -- Function: void* JvAllocBytes (jsize SIZE) - Allocates SIZE bytes from the heap. The memory returned is zeroed. - This memory is not scanned for pointers by the garbage collector, - but will be freed if no references to it are discovered. - - This function can be useful if you need to associate some native - data with a Java object. Using a CNI's special 'RawDataManaged' - type, native data allocated with 'JvAllocBytes' will be - automatically freed when the Java object itself becomes - unreachable. - -11.13.4 Posix signals ---------------------- - -On Posix based systems the 'libgcj' library uses several signals -internally. CNI code should not attempt to use the same signals as -doing so may cause 'libgcj' and/or the CNI code to fail. - - SIGSEGV is used on many systems to generate 'NullPointerExceptions'. -SIGCHLD is used internally by 'Runtime.exec()'. Several other signals -(that vary from platform to platform) can be used by the memory manager -and by 'Thread.interrupt()'. - - -File: gcj.info, Node: Exception Handling, Next: Synchronization, Prev: Mixing with C++, Up: About CNI - -11.14 Exception Handling -======================== - -While C++ and Java share a common exception handling framework, things -are not yet perfectly integrated. The main issue is that the run-time -type information facilities of the two languages are not integrated. - - Still, things work fairly well. You can throw a Java exception from -C++ using the ordinary 'throw' construct, and this exception can be -caught by Java code. Similarly, you can catch an exception thrown from -Java using the C++ 'catch' construct. - -Here is an example: - - if (i >= count) - throw new java::lang::IndexOutOfBoundsException(); - - Normally, G++ will automatically detect when you are writing C++ code -that uses Java exceptions, and handle them appropriately. However, if -C++ code only needs to execute destructors when Java exceptions are -thrown through it, GCC will guess incorrectly. Sample problematic code: - - struct S { ~S(); }; - - extern void bar(); // Is implemented in Java and may throw exceptions. - - void foo() - { - S s; - bar(); - } - - The usual effect of an incorrect guess is a link failure, complaining -of a missing routine called '__gxx_personality_v0'. - - You can inform the compiler that Java exceptions are to be used in a -translation unit, irrespective of what it might think, by writing -'#pragma GCC java_exceptions' at the head of the file. This '#pragma' -must appear before any functions that throw or catch exceptions, or run -destructors when exceptions are thrown through them. - - -File: gcj.info, Node: Synchronization, Next: Invocation, Prev: Exception Handling, Up: About CNI - -11.15 Synchronization -===================== - -Each Java object has an implicit monitor. The Java VM uses the -instruction 'monitorenter' to acquire and lock a monitor, and -'monitorexit' to release it. - - The corresponding CNI macros are 'JvMonitorEnter' and 'JvMonitorExit' -(JNI has similar methods 'MonitorEnter' and 'MonitorExit'). - - The Java source language does not provide direct access to these -primitives. Instead, there is a 'synchronized' statement that does an -implicit 'monitorenter' before entry to the block, and does a -'monitorexit' on exit from the block. Note that the lock has to be -released even when the block is abnormally terminated by an exception, -which means there is an implicit 'try finally' surrounding -synchronization locks. - - From C++, it makes sense to use a destructor to release a lock. CNI -defines the following utility class: - - class JvSynchronize() { - jobject obj; - JvSynchronize(jobject o) { obj = o; JvMonitorEnter(o); } - ~JvSynchronize() { JvMonitorExit(obj); } - }; - - So this Java code: - - synchronized (OBJ) - { - CODE - } - -might become this C++ code: - - { - JvSynchronize dummy (OBJ); - CODE; - } - - Java also has methods with the 'synchronized' attribute. This is -equivalent to wrapping the entire method body in a 'synchronized' -statement. (Alternatively, an implementation could require the caller -to do the synchronization. This is not practical for a compiler, -because each virtual method call would have to test at run-time if -synchronization is needed.) Since in 'gcj' the 'synchronized' attribute -is handled by the method implementation, it is up to the programmer of a -synchronized native method to handle the synchronization (in the C++ -implementation of the method). In other words, you need to manually add -'JvSynchronize' in a 'native synchronized' method. - - -File: gcj.info, Node: Invocation, Next: Reflection, Prev: Synchronization, Up: About CNI - -11.16 Invocation -================ - -CNI permits C++ applications to make calls into Java classes, in -addition to allowing Java code to call into C++. Several functions, -known as the "invocation API", are provided to support this. - - -- Function: jint JvCreateJavaVM (JvVMInitArgs* VM_ARGS) - - Initializes the Java runtime. This function performs essential - initialization of the threads interface, garbage collector, - exception handling and other key aspects of the runtime. It must - be called once by an application with a non-Java 'main()' function, - before any other Java or CNI calls are made. It is safe, but not - recommended, to call 'JvCreateJavaVM()' more than once provided it - is only called from a single thread. The VMARGS parameter can be - used to specify initialization parameters for the Java runtime. It - may be 'NULL'. - - JvVMInitArgs represents a list of virtual machine initialization - arguments. 'JvCreateJavaVM()' ignores the version field. - - typedef struct JvVMOption - { - // a VM initialization option - char* optionString; - // extra information associated with this option - void* extraInfo; - } JvVMOption; - - typedef struct JvVMInitArgs - { - // for compatibility with JavaVMInitArgs - jint version; - - // number of VM initialization options - jint nOptions; - - // an array of VM initialization options - JvVMOption* options; - - // true if the option parser should ignore unrecognized options - jboolean ignoreUnrecognized; - } JvVMInitArgs; - - 'JvCreateJavaVM()' returns '0' upon success, or '-1' if the runtime - is already initialized. - - _Note:_ In GCJ 3.1, the 'vm_args' parameter is ignored. It is - recognized and used as of release 4.0. - - -- Function: java::lang::Thread* JvAttachCurrentThread (jstring NAME, - java::lang::ThreadGroup* GROUP) - Registers an existing thread with the Java runtime. This must be - called once from each thread, before that thread makes any other - Java or CNI calls. It must be called after 'JvCreateJavaVM'. NAME - specifies a name for the thread. It may be 'NULL', in which case a - name will be generated. GROUP is the ThreadGroup in which this - thread will be a member. If it is 'NULL', the thread will be a - member of the main thread group. The return value is the Java - 'Thread' object that represents the thread. It is safe to call - 'JvAttachCurrentThread()' more than once from the same thread. If - the thread is already attached, the call is ignored and the current - thread object is returned. - - -- Function: jint JvDetachCurrentThread () - Unregisters a thread from the Java runtime. This should be called - by threads that were attached using 'JvAttachCurrentThread()', - after they have finished making calls to Java code. This ensures - that any resources associated with the thread become eligible for - garbage collection. This function returns '0' upon success, or - '-1' if the current thread is not attached. - -11.16.1 Handling uncaught exceptions ------------------------------------- - -If an exception is thrown from Java code called using the invocation -API, and no handler for the exception can be found, the runtime will -abort the application. In order to make the application more robust, it -is recommended that code which uses the invocation API be wrapped by a -top-level try/catch block that catches all Java exceptions. - -11.16.2 Example ---------------- - -The following code demonstrates the use of the invocation API. In this -example, the C++ application initializes the Java runtime and attaches -itself. The 'java.lang.System' class is initialized in order to access -its 'out' field, and a Java string is printed. Finally, the thread is -detached from the runtime once it has finished making Java calls. -Everything is wrapped with a try/catch block to provide a default -handler for any uncaught exceptions. - - The example can be compiled with 'c++ -c test.cc; gcj test.o'. - - // test.cc - #include <gcj/cni.h> - #include <java/lang/System.h> - #include <java/io/PrintStream.h> - #include <java/lang/Throwable.h> - - int main(int argc, char *argv[]) - { - using namespace java::lang; - - try - { - JvCreateJavaVM(NULL); - JvAttachCurrentThread(NULL, NULL); - - String *message = JvNewStringLatin1("Hello from C++"); - JvInitClass(&System::class$); - System::out->println(message); - - JvDetachCurrentThread(); - } - catch (Throwable *t) - { - System::err->println(JvNewStringLatin1("Unhandled Java exception:")); - t->printStackTrace(); - } - } - - -File: gcj.info, Node: Reflection, Prev: Invocation, Up: About CNI - -11.17 Reflection -================ - -Reflection is possible with CNI code, it functions similarly to how it -functions with JNI. - - The types 'jfieldID' and 'jmethodID' are as in JNI. - -The functions: - - * 'JvFromReflectedField', - * 'JvFromReflectedMethod', - * 'JvToReflectedField' - * 'JvToFromReflectedMethod' - -will be added shortly, as will other functions corresponding to JNI. - - -File: gcj.info, Node: System properties, Next: Resources, Prev: About CNI, Up: Top - -12 System properties -******************** - -The runtime behavior of the 'libgcj' library can be modified by setting -certain system properties. These properties can be compiled into the -program using the '-DNAME[=VALUE]' option to 'gcj' or by setting them -explicitly in the program by calling the -'java.lang.System.setProperty()' method. Some system properties are -only used for informational purposes (like giving a version number or a -user name). A program can inspect the current value of a property by -calling the 'java.lang.System.getProperty()' method. - -* Menu: - -* Standard Properties:: Standard properties supported by 'libgcj' -* GNU Classpath Properties:: Properties found in Classpath based libraries -* libgcj Runtime Properties:: Properties specific to 'libgcj' - - -File: gcj.info, Node: Standard Properties, Next: GNU Classpath Properties, Up: System properties - -12.1 Standard Properties -======================== - -The following properties are normally found in all implementations of -the core libraries for the Java language. - -'java.version' - The 'libgcj' version number. - -'java.vendor' - Set to 'The Free Software Foundation, Inc.' - -'java.vendor.url' - Set to <http://gcc.gnu.org/java/>. - -'java.home' - The directory where 'gcj' was installed. Taken from the '--prefix' - option given to 'configure'. - -'java.class.version' - The class format version number supported by the libgcj byte code - interpreter. (Currently '46.0') - -'java.vm.specification.version' - The Virtual Machine Specification version implemented by 'libgcj'. - (Currently '1.0') - -'java.vm.specification.vendor' - The name of the Virtual Machine specification designer. - -'java.vm.specification.name' - The name of the Virtual Machine specification (Set to 'Java Virtual - Machine Specification'). - -'java.vm.version' - The 'gcj' version number. - -'java.vm.vendor' - Set to 'The Free Software Foundation, Inc.' - -'java.vm.name' - Set to 'GNU libgcj'. - -'java.specification.version' - The Runtime Environment specification version implemented by - 'libgcj'. (Currently set to '1.3') - -'java.specification.vendor' - The Runtime Environment specification designer. - -'java.specification.name' - The name of the Runtime Environment specification (Set to 'Java - Platform API Specification'). - -'java.class.path' - The paths (jar files, zip files and directories) used for finding - class files. - -'java.library.path' - Directory path used for finding native libraries. - -'java.io.tmpdir' - The directory used to put temporary files in. - -'java.compiler' - Name of the Just In Time compiler to use by the byte code - interpreter. Currently not used in 'libgcj'. - -'java.ext.dirs' - Directories containing jar files with extra libraries. Will be - used when resolving classes. - -'java.protocol.handler.pkgs' - A '|' separated list of package names that is used to find classes - that implement handlers for 'java.net.URL'. - -'java.rmi.server.codebase' - A list of URLs that is used by the 'java.rmi.server.RMIClassLoader' - to load classes from. - -'jdbc.drivers' - A list of class names that will be loaded by the - 'java.sql.DriverManager' when it starts up. - -'file.separator' - The separator used in when directories are included in a filename - (normally '/' or '\' ). - -'file.encoding' - The default character encoding used when converting platform native - files to Unicode (usually set to '8859_1'). - -'path.separator' - The standard separator used when a string contains multiple paths - (normally ':' or ';'), the string is usually not a valid character - to use in normal directory names.) - -'line.separator' - The default line separator used on the platform (normally '\n', - '\r' or a combination of those two characters). - -'policy.provider' - The class name used for the default policy provider returned by - 'java.security.Policy.getPolicy'. - -'user.name' - The name of the user running the program. Can be the full name, - the login name or empty if unknown. - -'user.home' - The default directory to put user specific files in. - -'user.dir' - The current working directory from which the program was started. - -'user.language' - The default language as used by the 'java.util.Locale' class. - -'user.region' - The default region as used by the 'java.util.Local' class. - -'user.variant' - The default variant of the language and region local used. - -'user.timezone' - The default timezone as used by the 'java.util.TimeZone' class. - -'os.name' - The operating system/kernel name that the program runs on. - -'os.arch' - The hardware that we are running on. - -'os.version' - The version number of the operating system/kernel. - -'awt.appletWarning' - The string to display when an untrusted applet is displayed. - Returned by 'java.awt.Window.getWarningString()' when the window is - "insecure". - -'awt.toolkit' - The class name used for initializing the default - 'java.awt.Toolkit'. Defaults to 'gnu.awt.gtk.GtkToolkit'. - -'http.proxyHost' - Name of proxy host for http connections. - -'http.proxyPort' - Port number to use when a proxy host is in use. - - -File: gcj.info, Node: GNU Classpath Properties, Next: libgcj Runtime Properties, Prev: Standard Properties, Up: System properties - -12.2 GNU Classpath Properties -============================= - -'libgcj' is based on the GNU Classpath (Essential Libraries for Java) a -GNU project to create free core class libraries for use with virtual -machines and compilers for the Java language. The following properties -are common to libraries based on GNU Classpath. - -'gcj.dumpobject' - Enables printing serialization debugging by the - 'java.io.ObjectInput' and 'java.io.ObjectOutput' classes when set - to something else then the empty string. Only used when running a - debug build of the library. - -'gnu.classpath.vm.shortname' - This is a succinct name of the virtual machine. For 'libgcj', this - will always be 'libgcj'. - -'gnu.classpath.home.url' - A base URL used for finding system property files (e.g., - 'classpath.security'). By default this is a 'file:' URL pointing - to the 'lib' directory under 'java.home'. - - -File: gcj.info, Node: libgcj Runtime Properties, Prev: GNU Classpath Properties, Up: System properties - -12.3 libgcj Runtime Properties -============================== - -The following properties are specific to the 'libgcj' runtime and will -normally not be found in other core libraries for the java language. - -'java.fullversion' - The combination of 'java.vm.name' and 'java.vm.version'. - -'java.vm.info' - Same as 'java.fullversion'. - -'impl.prefix' - Used by the 'java.net.DatagramSocket' class when set to something - else then the empty string. When set all newly created - 'DatagramSocket's will try to load a class - 'java.net.[impl.prefix]DatagramSocketImpl' instead of the normal - 'java.net.PlainDatagramSocketImpl'. - -'gnu.gcj.progname' - The class or binary name that was used to invoke the program. This - will be the name of the "main" class in the case where the 'gij' - front end is used, or the program binary name in the case where an - application is compiled to a native binary. - -'gnu.gcj.user.realname' - The real name of the user, as taken from the password file. This - may not always hold only the user's name (as some sites put extra - information in this field). Also, this property is not available - on all platforms. - -'gnu.gcj.runtime.NameFinder.use_addr2line' - Whether an external process, 'addr2line', should be used to - determine line number information when tracing the stack. Setting - this to 'false' may suppress line numbers when printing stack - traces and when using the java.util.logging infrastructure. - However, performance may improve significantly for applications - that print stack traces or make logging calls frequently. - -'gnu.gcj.runtime.NameFinder.show_raw' - Whether the address of a stack frame should be printed when the - line number is unavailable. Setting this to 'true' will cause the - name of the object and the offset within that object to be printed - when no line number is available. This allows for off-line - decoding of stack traces if necessary debug information is - available. The default is 'false', no raw addresses are printed. - -'gnu.gcj.runtime.NameFinder.remove_unknown' - Whether stack frames for non-java code should be included in a - stack trace. The default value is 'true', stack frames for - non-java code are suppressed. Setting this to 'false' will cause - any non-java stack frames to be printed in addition to frames for - the java code. - -'gnu.gcj.runtime.VMClassLoader.library_control' - This controls how shared libraries are automatically loaded by the - built-in class loader. If this property is set to 'full', a full - search is done for each requested class. If this property is set - to 'cache', then any failed lookups are cached and not tried again. - If this property is set to 'never' (the default), then lookups are - never done. For more information, *Note Extensions::. - -'gnu.gcj.runtime.endorsed.dirs' - This is like the standard 'java.endorsed.dirs', property, but - specifies some extra directories which are searched after the - standard endorsed directories. This is primarily useful for - telling 'libgcj' about additional libraries which are ordinarily - incorporated into the JDK, and which should be loaded by the - bootstrap class loader, but which are not yet part of 'libgcj' - itself for some reason. - -'gnu.gcj.jit.compiler' - This is the full path to 'gcj' executable which should be used to - compile classes just-in-time when 'ClassLoader.defineClass' is - called. If not set, 'gcj' will not be invoked by the runtime; this - can also be controlled via 'Compiler.disable'. - -'gnu.gcj.jit.options' - This is a space-separated string of options which should be passed - to 'gcj' when in JIT mode. If not set, a sensible default is - chosen. - -'gnu.gcj.jit.cachedir' - This is the directory where cached shared library files are stored. - If not set, JIT compilation is disabled. This should never be set - to a directory that is writable by any other user. - -'gnu.gcj.precompiled.db.path' - This is a sequence of file names, each referring to a file created - by 'gcj-dbtool'. These files will be used by 'libgcj' to find - shared libraries corresponding to classes that are loaded from - bytecode. 'libgcj' often has a built-in default database; it can - be queried using 'gcj-dbtool -p'. - - -File: gcj.info, Node: Resources, Next: Index, Prev: System properties, Up: Top - -13 Resources -************ - -While writing 'gcj' and 'libgcj' we have, of course, relied heavily on -documentation from Sun Microsystems. In particular we have used The -Java Language Specification (both first and second editions), the Java -Class Libraries (volumes one and two), and the Java Virtual Machine -Specification. In addition we've used Sun's online documentation. - - The current 'gcj' home page is <http://gcc.gnu.org/java/>. - - For more information on GCC, see <http://gcc.gnu.org/>. - - Some 'libgcj' testing is done using the Mauve test suite. This is a -free software Java class library test suite which is being written -because the JCK is not free. See <http://www.sourceware.org/mauve/> for -more information. - - -File: gcj.info, Node: Index, Prev: Resources, Up: Top - -Index -***** - - -* Menu: - -* class path: Input Options. (line 6) -* class$: Reference types. (line 20) -* elements on template<class T>: Arrays. (line 45) -* FDL, GNU Free Documentation License: GNU Free Documentation License. - (line 6) -* GCJ_PROPERTIES: Extensions. (line 56) -* GCJ_PROPERTIES <1>: Extensions. (line 56) -* jclass: Reference types. (line 16) -* jobject: Reference types. (line 16) -* jstring: Reference types. (line 16) -* JvAllocBytes: Mixing with C++. (line 98) -* JvAttachCurrentThread: Invocation. (line 54) -* JvCreateJavaVM: Invocation. (line 10) -* JvDetachCurrentThread: Invocation. (line 68) -* JvFree: Memory allocation. (line 18) -* JvGetArrayLength: Arrays. (line 85) -* JvGetStringChars: Strings. (line 24) -* JvGetStringUTFLength: Strings. (line 28) -* JvGetStringUTFRegion: Strings. (line 32) -* JvMalloc: Memory allocation. (line 10) -* JvNewBooleanArray: Arrays. (line 82) -* JvNewObjectArray: Arrays. (line 55) -* JvNewString: Strings. (line 10) -* JvNewStringLatin1: Strings. (line 14) -* JvNewStringLatin1 <1>: Strings. (line 17) -* JvNewStringUTF: Strings. (line 20) -* JvPrimClass: Primitive types. (line 35) -* JvRealloc: Memory allocation. 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