From e3cc64dec20832769406aa38cde83c7dd4194bf4 Mon Sep 17 00:00:00 2001 From: Ben Cheng Date: Tue, 22 Apr 2014 13:33:12 -0700 Subject: [4.9] GCC 4.9.0 official release refresh Change-Id: Ic99a7da8b44b789a48aeec93b33e93944d6e6767 --- gcc-4.9/gcc/doc/gfortran.1 | 1411 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 1411 insertions(+) create mode 100644 gcc-4.9/gcc/doc/gfortran.1 (limited to 'gcc-4.9/gcc/doc/gfortran.1') diff --git a/gcc-4.9/gcc/doc/gfortran.1 b/gcc-4.9/gcc/doc/gfortran.1 new file mode 100644 index 000000000..285fdafd7 --- /dev/null +++ b/gcc-4.9/gcc/doc/gfortran.1 @@ -0,0 +1,1411 @@ +.\" Automatically generated by Pod::Man 2.27 (Pod::Simple 3.28) +.\" +.\" Standard preamble: +.\" ======================================================================== +.de Sp \" Vertical space (when we can't use .PP) +.if t .sp .5v +.if n .sp +.. +.de Vb \" Begin verbatim text +.ft CW +.nf +.ne \\$1 +.. +.de Ve \" End verbatim text +.ft R +.fi +.. +.\" Set up some character translations and predefined strings. \*(-- will +.\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left +.\" double quote, and \*(R" will give a right double quote. \*(C+ will +.\" give a nicer C++. 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Always turn off hyphenation; it makes +.\" way too many mistakes in technical documents. +.if n .ad l +.nh +.SH "NAME" +gfortran \- GNU Fortran compiler +.SH "SYNOPSIS" +.IX Header "SYNOPSIS" +gfortran [\fB\-c\fR|\fB\-S\fR|\fB\-E\fR] + [\fB\-g\fR] [\fB\-pg\fR] [\fB\-O\fR\fIlevel\fR] + [\fB\-W\fR\fIwarn\fR...] [\fB\-pedantic\fR] + [\fB\-I\fR\fIdir\fR...] [\fB\-L\fR\fIdir\fR...] + [\fB\-D\fR\fImacro\fR[=\fIdefn\fR]...] [\fB\-U\fR\fImacro\fR] + [\fB\-f\fR\fIoption\fR...] + [\fB\-m\fR\fImachine-option\fR...] + [\fB\-o\fR \fIoutfile\fR] \fIinfile\fR... +.PP +Only the most useful options are listed here; see below for the +remainder. +.SH "DESCRIPTION" +.IX Header "DESCRIPTION" +The \fBgfortran\fR command supports all the options supported by the +\&\fBgcc\fR command. Only options specific to \s-1GNU\s0 Fortran are documented +here. +.PP +All \s-1GCC\s0 and \s-1GNU\s0 Fortran options +are accepted both by \fBgfortran\fR and by \fBgcc\fR +(as well as any other drivers built at the same time, +such as \fBg++\fR), +since adding \s-1GNU\s0 Fortran to the \s-1GCC\s0 distribution +enables acceptance of \s-1GNU\s0 Fortran options +by all of the relevant drivers. +.PP +In some cases, options have positive and negative forms; +the negative form of \fB\-ffoo\fR would be \fB\-fno\-foo\fR. +This manual documents only one of these two forms, whichever +one is not the default. +.SH "OPTIONS" +.IX Header "OPTIONS" +Here is a summary of all the options specific to \s-1GNU\s0 Fortran, grouped +by type. Explanations are in the following sections. +.IP "\fIFortran Language Options\fR" 4 +.IX Item "Fortran Language Options" +\&\fB\-fall\-intrinsics \-fbackslash \-fcray\-pointer \-fd\-lines\-as\-code +\&\-fd\-lines\-as\-comments \-fdefault\-double\-8 \-fdefault\-integer\-8 +\&\-fdefault\-real\-8 \-fdollar\-ok \-ffixed\-line\-length\-\fR\fIn\fR +\&\fB\-ffixed\-line\-length\-none \-ffree\-form \-ffree\-line\-length\-\fR\fIn\fR +\&\fB\-ffree\-line\-length\-none \-fimplicit\-none \-finteger\-4\-integer\-8 +\&\-fmax\-identifier\-length \-fmodule\-private \-fno\-fixed\-form \-fno\-range\-check +\&\-fopenmp \-freal\-4\-real\-10 \-freal\-4\-real\-16 \-freal\-4\-real\-8 +\&\-freal\-8\-real\-10 \-freal\-8\-real\-16 \-freal\-8\-real\-4 \-std=\fR\fIstd\fR\fB \fR +.IP "\fIPreprocessing Options\fR" 4 +.IX Item "Preprocessing Options" +\&\fB\-A\-\fR\fIquestion\fR[\fB=\fR\fIanswer\fR] +\&\fB\-A\fR\fIquestion\fR\fB=\fR\fIanswer\fR \fB\-C \-CC \-D\fR\fImacro\fR[\fB=\fR\fIdefn\fR] +\&\fB\-H \-P +\&\-U\fR\fImacro\fR \fB\-cpp \-dD \-dI \-dM \-dN \-dU \-fworking\-directory +\&\-imultilib\fR \fIdir\fR +\&\fB\-iprefix\fR \fIfile\fR \fB\-iquote \-isysroot\fR \fIdir\fR \fB\-isystem\fR \fIdir\fR \fB\-nocpp +\&\-nostdinc +\&\-undef\fR +.IP "\fIError and Warning Options\fR" 4 +.IX Item "Error and Warning Options" +\&\fB\-Waliasing \-Wall \-Wampersand \-Warray\-bounds +\&\-Wc\-binding\-type \-Wcharacter\-truncation +\&\-Wconversion \-Wfunction\-elimination \-Wimplicit\-interface +\&\-Wimplicit\-procedure \-Wintrinsic\-shadow \-Wintrinsics\-std +\&\-Wline\-truncation \-Wno\-align\-commons \-Wno\-tabs \-Wreal\-q\-constant +\&\-Wsurprising \-Wunderflow \-Wunused\-parameter \-Wrealloc\-lhs \-Wrealloc\-lhs\-all +\&\-Wtarget\-lifetime \-fmax\-errors=\fR\fIn\fR \fB\-fsyntax\-only \-pedantic \-pedantic\-errors\fR +.IP "\fIDebugging Options\fR" 4 +.IX Item "Debugging Options" +\&\fB\-fbacktrace \-fdump\-fortran\-optimized \-fdump\-fortran\-original +\&\-fdump\-parse\-tree \-ffpe\-trap=\fR\fIlist\fR \fB\-ffpe\-summary=\fR\fIlist\fR\fB \fR +.IP "\fIDirectory Options\fR" 4 +.IX Item "Directory Options" +\&\fB\-I\fR\fIdir\fR \fB\-J\fR\fIdir\fR \fB\-fintrinsic\-modules\-path\fR \fIdir\fR +.IP "\fILink Options\fR" 4 +.IX Item "Link Options" +\&\fB\-static\-libgfortran\fR +.IP "\fIRuntime Options\fR" 4 +.IX Item "Runtime Options" +\&\fB\-fconvert=\fR\fIconversion\fR \fB\-fmax\-subrecord\-length=\fR\fIlength\fR +\&\fB\-frecord\-marker=\fR\fIlength\fR \fB\-fsign\-zero\fR +.IP "\fICode Generation Options\fR" 4 +.IX Item "Code Generation Options" +\&\fB\-faggressive\-function\-elimination \-fblas\-matmul\-limit=\fR\fIn\fR +\&\fB\-fbounds\-check \-fcheck\-array\-temporaries +\&\-fcheck=\fR\fI\fR +\&\fB\-fcoarray=\fR\fI\fR \fB\-fexternal\-blas \-ff2c +\&\-ffrontend\-optimize +\&\-finit\-character=\fR\fIn\fR \fB\-finit\-integer=\fR\fIn\fR \fB\-finit\-local\-zero +\&\-finit\-logical=\fR\fI\fR +\&\fB\-finit\-real=\fR\fI\fR +\&\fB\-fmax\-array\-constructor=\fR\fIn\fR \fB\-fmax\-stack\-var\-size=\fR\fIn\fR +\&\fB\-fno\-align\-commons +\&\-fno\-automatic \-fno\-protect\-parens \-fno\-underscoring +\&\-fsecond\-underscore \-fpack\-derived \-frealloc\-lhs \-frecursive +\&\-frepack\-arrays \-fshort\-enums \-fstack\-arrays\fR +.SS "Options controlling Fortran dialect" +.IX Subsection "Options controlling Fortran dialect" +The following options control the details of the Fortran dialect +accepted by the compiler: +.IP "\fB\-ffree\-form\fR" 4 +.IX Item "-ffree-form" +.PD 0 +.IP "\fB\-ffixed\-form\fR" 4 +.IX Item "-ffixed-form" +.PD +Specify the layout used by the source file. The free form layout +was introduced in Fortran 90. Fixed form was traditionally used in +older Fortran programs. When neither option is specified, the source +form is determined by the file extension. +.IP "\fB\-fall\-intrinsics\fR" 4 +.IX Item "-fall-intrinsics" +This option causes all intrinsic procedures (including the GNU-specific +extensions) to be accepted. This can be useful with \fB\-std=f95\fR to +force standard-compliance but get access to the full range of intrinsics +available with \fBgfortran\fR. As a consequence, \fB\-Wintrinsics\-std\fR +will be ignored and no user-defined procedure with the same name as any +intrinsic will be called except when it is explicitly declared \f(CW\*(C`EXTERNAL\*(C'\fR. +.IP "\fB\-fd\-lines\-as\-code\fR" 4 +.IX Item "-fd-lines-as-code" +.PD 0 +.IP "\fB\-fd\-lines\-as\-comments\fR" 4 +.IX Item "-fd-lines-as-comments" +.PD +Enable special treatment for lines beginning with \f(CW\*(C`d\*(C'\fR or \f(CW\*(C`D\*(C'\fR +in fixed form sources. If the \fB\-fd\-lines\-as\-code\fR option is +given they are treated as if the first column contained a blank. If the +\&\fB\-fd\-lines\-as\-comments\fR option is given, they are treated as +comment lines. +.IP "\fB\-fdollar\-ok\fR" 4 +.IX Item "-fdollar-ok" +Allow \fB$\fR as a valid non-first character in a symbol name. Symbols +that start with \fB$\fR are rejected since it is unclear which rules to +apply to implicit typing as different vendors implement different rules. +Using \fB$\fR in \f(CW\*(C`IMPLICIT\*(C'\fR statements is also rejected. +.IP "\fB\-fbackslash\fR" 4 +.IX Item "-fbackslash" +Change the interpretation of backslashes in string literals from a single +backslash character to \*(L"C\-style\*(R" escape characters. The following +combinations are expanded \f(CW\*(C`\ea\*(C'\fR, \f(CW\*(C`\eb\*(C'\fR, \f(CW\*(C`\ef\*(C'\fR, \f(CW\*(C`\en\*(C'\fR, +\&\f(CW\*(C`\er\*(C'\fR, \f(CW\*(C`\et\*(C'\fR, \f(CW\*(C`\ev\*(C'\fR, \f(CW\*(C`\e\e\*(C'\fR, and \f(CW\*(C`\e0\*(C'\fR to the \s-1ASCII\s0 +characters alert, backspace, form feed, newline, carriage return, +horizontal tab, vertical tab, backslash, and \s-1NUL,\s0 respectively. +Additionally, \f(CW\*(C`\ex\*(C'\fR\fInn\fR, \f(CW\*(C`\eu\*(C'\fR\fInnnn\fR and +\&\f(CW\*(C`\eU\*(C'\fR\fInnnnnnnn\fR (where each \fIn\fR is a hexadecimal digit) are +translated into the Unicode characters corresponding to the specified code +points. All other combinations of a character preceded by \e are +unexpanded. +.IP "\fB\-fmodule\-private\fR" 4 +.IX Item "-fmodule-private" +Set the default accessibility of module entities to \f(CW\*(C`PRIVATE\*(C'\fR. +Use-associated entities will not be accessible unless they are explicitly +declared as \f(CW\*(C`PUBLIC\*(C'\fR. +.IP "\fB\-ffixed\-line\-length\-\fR\fIn\fR" 4 +.IX Item "-ffixed-line-length-n" +Set column after which characters are ignored in typical fixed-form +lines in the source file, and through which spaces are assumed (as +if padded to that length) after the ends of short fixed-form lines. +.Sp +Popular values for \fIn\fR include 72 (the +standard and the default), 80 (card image), and 132 (corresponding +to \*(L"extended-source\*(R" options in some popular compilers). +\&\fIn\fR may also be \fBnone\fR, meaning that the entire line is meaningful +and that continued character constants never have implicit spaces appended +to them to fill out the line. +\&\fB\-ffixed\-line\-length\-0\fR means the same thing as +\&\fB\-ffixed\-line\-length\-none\fR. +.IP "\fB\-ffree\-line\-length\-\fR\fIn\fR" 4 +.IX Item "-ffree-line-length-n" +Set column after which characters are ignored in typical free-form +lines in the source file. The default value is 132. +\&\fIn\fR may be \fBnone\fR, meaning that the entire line is meaningful. +\&\fB\-ffree\-line\-length\-0\fR means the same thing as +\&\fB\-ffree\-line\-length\-none\fR. +.IP "\fB\-fmax\-identifier\-length=\fR\fIn\fR" 4 +.IX Item "-fmax-identifier-length=n" +Specify the maximum allowed identifier length. Typical values are +31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008). +.IP "\fB\-fimplicit\-none\fR" 4 +.IX Item "-fimplicit-none" +Specify that no implicit typing is allowed, unless overridden by explicit +\&\f(CW\*(C`IMPLICIT\*(C'\fR statements. This is the equivalent of adding +\&\f(CW\*(C`implicit none\*(C'\fR to the start of every procedure. +.IP "\fB\-fcray\-pointer\fR" 4 +.IX Item "-fcray-pointer" +Enable the Cray pointer extension, which provides C\-like pointer +functionality. +.IP "\fB\-fopenmp\fR" 4 +.IX Item "-fopenmp" +Enable the OpenMP extensions. This includes OpenMP \f(CW\*(C`!$omp\*(C'\fR directives +in free form +and \f(CW\*(C`c$omp\*(C'\fR, \f(CW*$omp\fR and \f(CW\*(C`!$omp\*(C'\fR directives in fixed form, +\&\f(CW\*(C`!$\*(C'\fR conditional compilation sentinels in free form +and \f(CW\*(C`c$\*(C'\fR, \f(CW\*(C`*$\*(C'\fR and \f(CW\*(C`!$\*(C'\fR sentinels in fixed form, +and when linking arranges for the OpenMP runtime library to be linked +in. The option \fB\-fopenmp\fR implies \fB\-frecursive\fR. +.IP "\fB\-fno\-range\-check\fR" 4 +.IX Item "-fno-range-check" +Disable range checking on results of simplification of constant +expressions during compilation. For example, \s-1GNU\s0 Fortran will give +an error at compile time when simplifying \f(CW\*(C`a = 1. / 0\*(C'\fR. +With this option, no error will be given and \f(CW\*(C`a\*(C'\fR will be assigned +the value \f(CW\*(C`+Infinity\*(C'\fR. If an expression evaluates to a value +outside of the relevant range of [\f(CW\*(C`\-HUGE()\*(C'\fR:\f(CW\*(C`HUGE()\*(C'\fR], +then the expression will be replaced by \f(CW\*(C`\-Inf\*(C'\fR or \f(CW\*(C`+Inf\*(C'\fR +as appropriate. +Similarly, \f(CW\*(C`DATA i/Z\*(AqFFFFFFFF\*(Aq/\*(C'\fR will result in an integer overflow +on most systems, but with \fB\-fno\-range\-check\fR the value will +\&\*(L"wrap around\*(R" and \f(CW\*(C`i\*(C'\fR will be initialized to \-1 instead. +.IP "\fB\-fdefault\-integer\-8\fR" 4 +.IX Item "-fdefault-integer-8" +Set the default integer and logical types to an 8 byte wide type. This option +also affects the kind of integer constants like \f(CW42\fR. Unlike +\&\fB\-finteger\-4\-integer\-8\fR, it does not promote variables with explicit +kind declaration. +.IP "\fB\-fdefault\-real\-8\fR" 4 +.IX Item "-fdefault-real-8" +Set the default real type to an 8 byte wide type. This option also affects +the kind of non-double real constants like \f(CW1.0\fR, and does promote +the default width of \f(CW\*(C`DOUBLE PRECISION\*(C'\fR to 16 bytes if possible, unless +\&\f(CW\*(C`\-fdefault\-double\-8\*(C'\fR is given, too. Unlike \fB\-freal\-4\-real\-8\fR, +it does not promote variables with explicit kind declaration. +.IP "\fB\-fdefault\-double\-8\fR" 4 +.IX Item "-fdefault-double-8" +Set the \f(CW\*(C`DOUBLE PRECISION\*(C'\fR type to an 8 byte wide type. Do nothing if this +is already the default. If \fB\-fdefault\-real\-8\fR is given, +\&\f(CW\*(C`DOUBLE PRECISION\*(C'\fR would instead be promoted to 16 bytes if possible, and +\&\fB\-fdefault\-double\-8\fR can be used to prevent this. The kind of real +constants like \f(CW\*(C`1.d0\*(C'\fR will not be changed by \fB\-fdefault\-real\-8\fR +though, so also \fB\-fdefault\-double\-8\fR does not affect it. +.IP "\fB\-finteger\-4\-integer\-8\fR" 4 +.IX Item "-finteger-4-integer-8" +Promote all \f(CW\*(C`INTEGER(KIND=4)\*(C'\fR entities to an \f(CW\*(C`INTEGER(KIND=8)\*(C'\fR +entities. If \f(CW\*(C`KIND=8\*(C'\fR is unavailable, then an error will be issued. +This option should be used with care and may not be suitable for your codes. +Areas of possible concern include calls to external procedures, +alignment in \f(CW\*(C`EQUIVALENCE\*(C'\fR and/or \f(CW\*(C`COMMON\*(C'\fR, generic interfaces, +\&\s-1BOZ\s0 literal constant conversion, and I/O. Inspection of the intermediate +representation of the translated Fortran code, produced by +\&\fB\-fdump\-tree\-original\fR, is suggested. +.IP "\fB\-freal\-4\-real\-8\fR" 4 +.IX Item "-freal-4-real-8" +.PD 0 +.IP "\fB\-freal\-4\-real\-10\fR" 4 +.IX Item "-freal-4-real-10" +.IP "\fB\-freal\-4\-real\-16\fR" 4 +.IX Item "-freal-4-real-16" +.IP "\fB\-freal\-8\-real\-4\fR" 4 +.IX Item "-freal-8-real-4" +.IP "\fB\-freal\-8\-real\-10\fR" 4 +.IX Item "-freal-8-real-10" +.IP "\fB\-freal\-8\-real\-16\fR" 4 +.IX Item "-freal-8-real-16" +.PD +Promote all \f(CW\*(C`REAL(KIND=M)\*(C'\fR entities to \f(CW\*(C`REAL(KIND=N)\*(C'\fR entities. +If \f(CW\*(C`REAL(KIND=N)\*(C'\fR is unavailable, then an error will be issued. +All other real kind types are unaffected by this option. +These options should be used with care and may not be suitable for your +codes. Areas of possible concern include calls to external procedures, +alignment in \f(CW\*(C`EQUIVALENCE\*(C'\fR and/or \f(CW\*(C`COMMON\*(C'\fR, generic interfaces, +\&\s-1BOZ\s0 literal constant conversion, and I/O. Inspection of the intermediate +representation of the translated Fortran code, produced by +\&\fB\-fdump\-tree\-original\fR, is suggested. +.IP "\fB\-std=\fR\fIstd\fR" 4 +.IX Item "-std=std" +Specify the standard to which the program is expected to conform, which +may be one of \fBf95\fR, \fBf2003\fR, \fBf2008\fR, \fBgnu\fR, or +\&\fBlegacy\fR. The default value for \fIstd\fR is \fBgnu\fR, which +specifies a superset of the Fortran 95 standard that includes all of the +extensions supported by \s-1GNU\s0 Fortran, although warnings will be given for +obsolete extensions not recommended for use in new code. The +\&\fBlegacy\fR value is equivalent but without the warnings for obsolete +extensions, and may be useful for old non-standard programs. The +\&\fBf95\fR, \fBf2003\fR and \fBf2008\fR values specify strict +conformance to the Fortran 95, Fortran 2003 and Fortran 2008 standards, +respectively; errors are given for all extensions beyond the relevant +language standard, and warnings are given for the Fortran 77 features +that are permitted but obsolescent in later standards. \fB\-std=f2008ts\fR +allows the Fortran 2008 standard including the additions of the +Technical Specification (\s-1TS\s0) 29113 on Further Interoperability of Fortran +with C. +.SS "Enable and customize preprocessing" +.IX Subsection "Enable and customize preprocessing" +Preprocessor related options. See section +\&\fBPreprocessing and conditional compilation\fR for more detailed +information on preprocessing in \fBgfortran\fR. +.IP "\fB\-cpp\fR" 4 +.IX Item "-cpp" +.PD 0 +.IP "\fB\-nocpp\fR" 4 +.IX Item "-nocpp" +.PD +Enable preprocessing. The preprocessor is automatically invoked if +the file extension is \fI.fpp\fR, \fI.FPP\fR, \fI.F\fR, \fI.FOR\fR, +\&\fI.FTN\fR, \fI.F90\fR, \fI.F95\fR, \fI.F03\fR or \fI.F08\fR. Use +this option to manually enable preprocessing of any kind of Fortran file. +.Sp +To disable preprocessing of files with any of the above listed extensions, +use the negative form: \fB\-nocpp\fR. +.Sp +The preprocessor is run in traditional mode. Any restrictions of the +file-format, especially the limits on line length, apply for +preprocessed output as well, so it might be advisable to use the +\&\fB\-ffree\-line\-length\-none\fR or \fB\-ffixed\-line\-length\-none\fR +options. +.IP "\fB\-dM\fR" 4 +.IX Item "-dM" +Instead of the normal output, generate a list of \f(CW\*(Aq#define\*(Aq\fR +directives for all the macros defined during the execution of the +preprocessor, including predefined macros. This gives you a way +of finding out what is predefined in your version of the preprocessor. +Assuming you have no file \fIfoo.f90\fR, the command +.Sp +.Vb 1 +\& touch foo.f90; gfortran \-cpp \-E \-dM foo.f90 +.Ve +.Sp +will show all the predefined macros. +.IP "\fB\-dD\fR" 4 +.IX Item "-dD" +Like \fB\-dM\fR except in two respects: it does not include the +predefined macros, and it outputs both the \f(CW\*(C`#define\*(C'\fR directives +and the result of preprocessing. Both kinds of output go to the +standard output file. +.IP "\fB\-dN\fR" 4 +.IX Item "-dN" +Like \fB\-dD\fR, but emit only the macro names, not their expansions. +.IP "\fB\-dU\fR" 4 +.IX Item "-dU" +Like \fBdD\fR except that only macros that are expanded, or whose +definedness is tested in preprocessor directives, are output; the +output is delayed until the use or test of the macro; and \f(CW\*(Aq#undef\*(Aq\fR +directives are also output for macros tested but undefined at the time. +.IP "\fB\-dI\fR" 4 +.IX Item "-dI" +Output \f(CW\*(Aq#include\*(Aq\fR directives in addition to the result +of preprocessing. +.IP "\fB\-fworking\-directory\fR" 4 +.IX Item "-fworking-directory" +Enable generation of linemarkers in the preprocessor output that will +let the compiler know the current working directory at the time of +preprocessing. When this option is enabled, the preprocessor will emit, +after the initial linemarker, a second linemarker with the current +working directory followed by two slashes. \s-1GCC\s0 will use this directory, +when it is present in the preprocessed input, as the directory emitted +as the current working directory in some debugging information formats. +This option is implicitly enabled if debugging information is enabled, +but this can be inhibited with the negated form +\&\fB\-fno\-working\-directory\fR. If the \fB\-P\fR flag is present +in the command line, this option has no effect, since no \f(CW\*(C`#line\*(C'\fR +directives are emitted whatsoever. +.IP "\fB\-idirafter\fR \fIdir\fR" 4 +.IX Item "-idirafter dir" +Search \fIdir\fR for include files, but do it after all directories +specified with \fB\-I\fR and the standard system directories have +been exhausted. \fIdir\fR is treated as a system include directory. +If dir begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced by +the sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR. +.IP "\fB\-imultilib\fR \fIdir\fR" 4 +.IX Item "-imultilib dir" +Use \fIdir\fR as a subdirectory of the directory containing target-specific +\&\*(C+ headers. +.IP "\fB\-iprefix\fR \fIprefix\fR" 4 +.IX Item "-iprefix prefix" +Specify \fIprefix\fR as the prefix for subsequent \fB\-iwithprefix\fR +options. If the \fIprefix\fR represents a directory, you should include +the final \f(CW\*(Aq/\*(Aq\fR. +.IP "\fB\-isysroot\fR \fIdir\fR" 4 +.IX Item "-isysroot dir" +This option is like the \fB\-\-sysroot\fR option, but applies only to +header files. See the \fB\-\-sysroot\fR option for more information. +.IP "\fB\-iquote\fR \fIdir\fR" 4 +.IX Item "-iquote dir" +Search \fIdir\fR only for header files requested with \f(CW\*(C`#include "file"\*(C'\fR; +they are not searched for \f(CW\*(C`#include \*(C'\fR, before all directories +specified by \fB\-I\fR and before the standard system directories. If +\&\fIdir\fR begins with \f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced by the +sysroot prefix; see \fB\-\-sysroot\fR and \fB\-isysroot\fR. +.IP "\fB\-isystem\fR \fIdir\fR" 4 +.IX Item "-isystem dir" +Search \fIdir\fR for header files, after all directories specified by +\&\fB\-I\fR but before the standard system directories. Mark it as a +system directory, so that it gets the same special treatment as is +applied to the standard system directories. If \fIdir\fR begins with +\&\f(CW\*(C`=\*(C'\fR, then the \f(CW\*(C`=\*(C'\fR will be replaced by the sysroot prefix; +see \fB\-\-sysroot\fR and \fB\-isysroot\fR. +.IP "\fB\-nostdinc\fR" 4 +.IX Item "-nostdinc" +Do not search the standard system directories for header files. Only +the directories you have specified with \fB\-I\fR options (and the +directory of the current file, if appropriate) are searched. +.IP "\fB\-undef\fR" 4 +.IX Item "-undef" +Do not predefine any system-specific or GCC-specific macros. +The standard predefined macros remain defined. +.IP "\fB\-A\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4 +.IX Item "-Apredicate=answer" +Make an assertion with the predicate \fIpredicate\fR and answer \fIanswer\fR. +This form is preferred to the older form \-A predicate(answer), which is still +supported, because it does not use shell special characters. +.IP "\fB\-A\-\fR\fIpredicate\fR\fB=\fR\fIanswer\fR" 4 +.IX Item "-A-predicate=answer" +Cancel an assertion with the predicate \fIpredicate\fR and answer \fIanswer\fR. +.IP "\fB\-C\fR" 4 +.IX Item "-C" +Do not discard comments. All comments are passed through to the output +file, except for comments in processed directives, which are deleted +along with the directive. +.Sp +You should be prepared for side effects when using \fB\-C\fR; it causes +the preprocessor to treat comments as tokens in their own right. For example, +comments appearing at the start of what would be a directive line have the +effect of turning that line into an ordinary source line, since the first +token on the line is no longer a \f(CW\*(Aq#\*(Aq\fR. +.Sp +Warning: this currently handles C\-Style comments only. The preprocessor +does not yet recognize Fortran-style comments. +.IP "\fB\-CC\fR" 4 +.IX Item "-CC" +Do not discard comments, including during macro expansion. This is like +\&\fB\-C\fR, except that comments contained within macros are also passed +through to the output file where the macro is expanded. +.Sp +In addition to the side-effects of the \fB\-C\fR option, the \fB\-CC\fR +option causes all \*(C+\-style comments inside a macro to be converted to C\-style +comments. This is to prevent later use of that macro from inadvertently +commenting out the remainder of the source line. The \fB\-CC\fR option +is generally used to support lint comments. +.Sp +Warning: this currently handles C\- and \*(C+\-Style comments only. The +preprocessor does not yet recognize Fortran-style comments. +.IP "\fB\-D\fR\fIname\fR" 4 +.IX Item "-Dname" +Predefine name as a macro, with definition \f(CW1\fR. +.IP "\fB\-D\fR\fIname\fR\fB=\fR\fIdefinition\fR" 4 +.IX Item "-Dname=definition" +The contents of \fIdefinition\fR are tokenized and processed as if they +appeared during translation phase three in a \f(CW\*(Aq#define\*(Aq\fR directive. +In particular, the definition will be truncated by embedded newline +characters. +.Sp +If you are invoking the preprocessor from a shell or shell-like program +you may need to use the shell's quoting syntax to protect characters such +as spaces that have a meaning in the shell syntax. +.Sp +If you wish to define a function-like macro on the command line, write +its argument list with surrounding parentheses before the equals sign +(if any). Parentheses are meaningful to most shells, so you will need +to quote the option. With sh and csh, \f(CW\*(C`\-D\*(Aqname(args...)=definition\*(Aq\*(C'\fR +works. +.Sp +\&\fB\-D\fR and \fB\-U\fR options are processed in the order they are +given on the command line. All \-imacros file and \-include file options +are processed after all \-D and \-U options. +.IP "\fB\-H\fR" 4 +.IX Item "-H" +Print the name of each header file used, in addition to other normal +activities. Each name is indented to show how deep in the \f(CW\*(Aq#include\*(Aq\fR +stack it is. +.IP "\fB\-P\fR" 4 +.IX Item "-P" +Inhibit generation of linemarkers in the output from the preprocessor. +This might be useful when running the preprocessor on something that +is not C code, and will be sent to a program which might be confused +by the linemarkers. +.IP "\fB\-U\fR\fIname\fR" 4 +.IX Item "-Uname" +Cancel any previous definition of \fIname\fR, either built in or provided +with a \fB\-D\fR option. +.SS "Options to request or suppress errors and warnings" +.IX Subsection "Options to request or suppress errors and warnings" +Errors are diagnostic messages that report that the \s-1GNU\s0 Fortran compiler +cannot compile the relevant piece of source code. The compiler will +continue to process the program in an attempt to report further errors +to aid in debugging, but will not produce any compiled output. +.PP +Warnings are diagnostic messages that report constructions which +are not inherently erroneous but which are risky or suggest there is +likely to be a bug in the program. Unless \fB\-Werror\fR is specified, +they do not prevent compilation of the program. +.PP +You can request many specific warnings with options beginning \fB\-W\fR, +for example \fB\-Wimplicit\fR to request warnings on implicit +declarations. Each of these specific warning options also has a +negative form beginning \fB\-Wno\-\fR to turn off warnings; +for example, \fB\-Wno\-implicit\fR. This manual lists only one of the +two forms, whichever is not the default. +.PP +These options control the amount and kinds of errors and warnings produced +by \s-1GNU\s0 Fortran: +.IP "\fB\-fmax\-errors=\fR\fIn\fR" 4 +.IX Item "-fmax-errors=n" +Limits the maximum number of error messages to \fIn\fR, at which point +\&\s-1GNU\s0 Fortran bails out rather than attempting to continue processing the +source code. If \fIn\fR is 0, there is no limit on the number of error +messages produced. +.IP "\fB\-fsyntax\-only\fR" 4 +.IX Item "-fsyntax-only" +Check the code for syntax errors, but do not actually compile it. This +will generate module files for each module present in the code, but no +other output file. +.IP "\fB\-pedantic\fR" 4 +.IX Item "-pedantic" +Issue warnings for uses of extensions to Fortran 95. +\&\fB\-pedantic\fR also applies to C\-language constructs where they +occur in \s-1GNU\s0 Fortran source files, such as use of \fB\ee\fR in a +character constant within a directive like \f(CW\*(C`#include\*(C'\fR. +.Sp +Valid Fortran 95 programs should compile properly with or without +this option. +However, without this option, certain \s-1GNU\s0 extensions and traditional +Fortran features are supported as well. +With this option, many of them are rejected. +.Sp +Some users try to use \fB\-pedantic\fR to check programs for conformance. +They soon find that it does not do quite what they want\-\-\-it finds some +nonstandard practices, but not all. +However, improvements to \s-1GNU\s0 Fortran in this area are welcome. +.Sp +This should be used in conjunction with \fB\-std=f95\fR, +\&\fB\-std=f2003\fR or \fB\-std=f2008\fR. +.IP "\fB\-pedantic\-errors\fR" 4 +.IX Item "-pedantic-errors" +Like \fB\-pedantic\fR, except that errors are produced rather than +warnings. +.IP "\fB\-Wall\fR" 4 +.IX Item "-Wall" +Enables commonly used warning options pertaining to usage that +we recommend avoiding and that we believe are easy to avoid. +This currently includes \fB\-Waliasing\fR, \fB\-Wampersand\fR, +\&\fB\-Wconversion\fR, \fB\-Wsurprising\fR, \fB\-Wc\-binding\-type\fR, +\&\fB\-Wintrinsics\-std\fR, \fB\-Wno\-tabs\fR, \fB\-Wintrinsic\-shadow\fR, +\&\fB\-Wline\-truncation\fR, \fB\-Wtarget\-lifetime\fR, +\&\fB\-Wreal\-q\-constant\fR and \fB\-Wunused\fR. +.IP "\fB\-Waliasing\fR" 4 +.IX Item "-Waliasing" +Warn about possible aliasing of dummy arguments. Specifically, it warns +if the same actual argument is associated with a dummy argument with +\&\f(CW\*(C`INTENT(IN)\*(C'\fR and a dummy argument with \f(CW\*(C`INTENT(OUT)\*(C'\fR in a call +with an explicit interface. +.Sp +The following example will trigger the warning. +.Sp +.Vb 7 +\& interface +\& subroutine bar(a,b) +\& integer, intent(in) :: a +\& integer, intent(out) :: b +\& end subroutine +\& end interface +\& integer :: a +\& +\& call bar(a,a) +.Ve +.IP "\fB\-Wampersand\fR" 4 +.IX Item "-Wampersand" +Warn about missing ampersand in continued character constants. The warning is +given with \fB\-Wampersand\fR, \fB\-pedantic\fR, \fB\-std=f95\fR, +\&\fB\-std=f2003\fR and \fB\-std=f2008\fR. Note: With no ampersand +given in a continued character constant, \s-1GNU\s0 Fortran assumes continuation +at the first non-comment, non-whitespace character after the ampersand +that initiated the continuation. +.IP "\fB\-Warray\-temporaries\fR" 4 +.IX Item "-Warray-temporaries" +Warn about array temporaries generated by the compiler. The information +generated by this warning is sometimes useful in optimization, in order to +avoid such temporaries. +.IP "\fB\-Wc\-binding\-type\fR" 4 +.IX Item "-Wc-binding-type" +Warn if the a variable might not be C interoperable. In particular, warn if +the variable has been declared using an intrinsic type with default kind +instead of using a kind parameter defined for C interoperability in the +intrinsic \f(CW\*(C`ISO_C_Binding\*(C'\fR module. This option is implied by +\&\fB\-Wall\fR. +.IP "\fB\-Wcharacter\-truncation\fR" 4 +.IX Item "-Wcharacter-truncation" +Warn when a character assignment will truncate the assigned string. +.IP "\fB\-Wline\-truncation\fR" 4 +.IX Item "-Wline-truncation" +Warn when a source code line will be truncated. This option is +implied by \fB\-Wall\fR. +.IP "\fB\-Wconversion\fR" 4 +.IX Item "-Wconversion" +Warn about implicit conversions that are likely to change the value of +the expression after conversion. Implied by \fB\-Wall\fR. +.IP "\fB\-Wconversion\-extra\fR" 4 +.IX Item "-Wconversion-extra" +Warn about implicit conversions between different types and kinds. +.IP "\fB\-Wextra\fR" 4 +.IX Item "-Wextra" +Enables some warning options for usages of language features which +may be problematic. This currently includes \fB\-Wcompare\-reals\fR +and \fB\-Wunused\-parameter\fR. +.IP "\fB\-Wimplicit\-interface\fR" 4 +.IX Item "-Wimplicit-interface" +Warn if a procedure is called without an explicit interface. +Note this only checks that an explicit interface is present. It does not +check that the declared interfaces are consistent across program units. +.IP "\fB\-Wimplicit\-procedure\fR" 4 +.IX Item "-Wimplicit-procedure" +Warn if a procedure is called that has neither an explicit interface +nor has been declared as \f(CW\*(C`EXTERNAL\*(C'\fR. +.IP "\fB\-Wintrinsics\-std\fR" 4 +.IX Item "-Wintrinsics-std" +Warn if \fBgfortran\fR finds a procedure named like an intrinsic not +available in the currently selected standard (with \fB\-std\fR) and treats +it as \f(CW\*(C`EXTERNAL\*(C'\fR procedure because of this. \fB\-fall\-intrinsics\fR can +be used to never trigger this behavior and always link to the intrinsic +regardless of the selected standard. +.IP "\fB\-Wreal\-q\-constant\fR" 4 +.IX Item "-Wreal-q-constant" +Produce a warning if a real-literal-constant contains a \f(CW\*(C`q\*(C'\fR +exponent-letter. +.IP "\fB\-Wsurprising\fR" 4 +.IX Item "-Wsurprising" +Produce a warning when \*(L"suspicious\*(R" code constructs are encountered. +While technically legal these usually indicate that an error has been made. +.Sp +This currently produces a warning under the following circumstances: +.RS 4 +.IP "\(bu" 4 +An \s-1INTEGER SELECT\s0 construct has a \s-1CASE\s0 that can never be matched as its +lower value is greater than its upper value. +.IP "\(bu" 4 +A \s-1LOGICAL SELECT\s0 construct has three \s-1CASE\s0 statements. +.IP "\(bu" 4 +A \s-1TRANSFER\s0 specifies a source that is shorter than the destination. +.IP "\(bu" 4 +The type of a function result is declared more than once with the same type. If +\&\fB\-pedantic\fR or standard-conforming mode is enabled, this is an error. +.IP "\(bu" 4 +A \f(CW\*(C`CHARACTER\*(C'\fR variable is declared with negative length. +.RE +.RS 4 +.RE +.IP "\fB\-Wtabs\fR" 4 +.IX Item "-Wtabs" +By default, tabs are accepted as whitespace, but tabs are not members +of the Fortran Character Set. For continuation lines, a tab followed +by a digit between 1 and 9 is supported. \fB\-Wno\-tabs\fR will cause +a warning to be issued if a tab is encountered. Note, \fB\-Wno\-tabs\fR +is active for \fB\-pedantic\fR, \fB\-std=f95\fR, \fB\-std=f2003\fR, +\&\fB\-std=f2008\fR and \fB\-Wall\fR. +.IP "\fB\-Wunderflow\fR" 4 +.IX Item "-Wunderflow" +Produce a warning when numerical constant expressions are +encountered, which yield an \s-1UNDERFLOW\s0 during compilation. +.IP "\fB\-Wintrinsic\-shadow\fR" 4 +.IX Item "-Wintrinsic-shadow" +Warn if a user-defined procedure or module procedure has the same name as an +intrinsic; in this case, an explicit interface or \f(CW\*(C`EXTERNAL\*(C'\fR or +\&\f(CW\*(C`INTRINSIC\*(C'\fR declaration might be needed to get calls later resolved to +the desired intrinsic/procedure. This option is implied by \fB\-Wall\fR. +.IP "\fB\-Wunused\-dummy\-argument\fR" 4 +.IX Item "-Wunused-dummy-argument" +Warn about unused dummy arguments. This option is implied by \fB\-Wall\fR. +.IP "\fB\-Wunused\-parameter\fR" 4 +.IX Item "-Wunused-parameter" +Contrary to \fBgcc\fR's meaning of \fB\-Wunused\-parameter\fR, +\&\fBgfortran\fR's implementation of this option does not warn +about unused dummy arguments (see \fB\-Wunused\-dummy\-argument\fR), +but about unused \f(CW\*(C`PARAMETER\*(C'\fR values. \fB\-Wunused\-parameter\fR +is not included in \fB\-Wall\fR but is implied by \fB\-Wall \-Wextra\fR. +.IP "\fB\-Walign\-commons\fR" 4 +.IX Item "-Walign-commons" +By default, \fBgfortran\fR warns about any occasion of variables being +padded for proper alignment inside a \f(CW\*(C`COMMON\*(C'\fR block. This warning can be turned +off via \fB\-Wno\-align\-commons\fR. See also \fB\-falign\-commons\fR. +.IP "\fB\-Wfunction\-elimination\fR" 4 +.IX Item "-Wfunction-elimination" +Warn if any calls to functions are eliminated by the optimizations +enabled by the \fB\-ffrontend\-optimize\fR option. +.IP "\fB\-Wrealloc\-lhs\fR" 4 +.IX Item "-Wrealloc-lhs" +Warn when the compiler might insert code to for allocation or reallocation of +an allocatable array variable of intrinsic type in intrinsic assignments. In +hot loops, the Fortran 2003 reallocation feature may reduce the performance. +If the array is already allocated with the correct shape, consider using a +whole-array array-spec (e.g. \f(CW\*(C`(:,:,:)\*(C'\fR) for the variable on the left-hand +side to prevent the reallocation check. Note that in some cases the warning +is shown, even if the compiler will optimize reallocation checks away. For +instance, when the right-hand side contains the same variable multiplied by +a scalar. See also \fB\-frealloc\-lhs\fR. +.IP "\fB\-Wrealloc\-lhs\-all\fR" 4 +.IX Item "-Wrealloc-lhs-all" +Warn when the compiler inserts code to for allocation or reallocation of an +allocatable variable; this includes scalars and derived types. +.IP "\fB\-Wcompare\-reals\fR" 4 +.IX Item "-Wcompare-reals" +Warn when comparing real or complex types for equality or inequality. +This option is implied by \fB\-Wextra\fR. +.IP "\fB\-Wtarget\-lifetime\fR" 4 +.IX Item "-Wtarget-lifetime" +Warn if the pointer in a pointer assignment might be longer than the its +target. This option is implied by \fB\-Wall\fR. +.IP "\fB\-Wzerotrip\fR" 4 +.IX Item "-Wzerotrip" +Warn if a \f(CW\*(C`DO\*(C'\fR loop is known to execute zero times at compile +time. This option is implied by \fB\-Wall\fR. +.IP "\fB\-Werror\fR" 4 +.IX Item "-Werror" +Turns all warnings into errors. +.PP +Some of these have no effect when compiling programs written in Fortran. +.SS "Options for debugging your program or \s-1GNU\s0 Fortran" +.IX Subsection "Options for debugging your program or GNU Fortran" +\&\s-1GNU\s0 Fortran has various special options that are used for debugging +either your program or the \s-1GNU\s0 Fortran compiler. +.IP "\fB\-fdump\-fortran\-original\fR" 4 +.IX Item "-fdump-fortran-original" +Output the internal parse tree after translating the source program +into internal representation. Only really useful for debugging the +\&\s-1GNU\s0 Fortran compiler itself. +.IP "\fB\-fdump\-fortran\-optimized\fR" 4 +.IX Item "-fdump-fortran-optimized" +Output the parse tree after front-end optimization. Only really +useful for debugging the \s-1GNU\s0 Fortran compiler itself. +.IP "\fB\-fdump\-parse\-tree\fR" 4 +.IX Item "-fdump-parse-tree" +Output the internal parse tree after translating the source program +into internal representation. Only really useful for debugging the +\&\s-1GNU\s0 Fortran compiler itself. This option is deprecated; use +\&\f(CW\*(C`\-fdump\-fortran\-original\*(C'\fR instead. +.IP "\fB\-ffpe\-trap=\fR\fIlist\fR" 4 +.IX Item "-ffpe-trap=list" +Specify a list of floating point exception traps to enable. On most +systems, if a floating point exception occurs and the trap for that +exception is enabled, a \s-1SIGFPE\s0 signal will be sent and the program +being aborted, producing a core file useful for debugging. \fIlist\fR +is a (possibly empty) comma-separated list of the following +exceptions: \fBinvalid\fR (invalid floating point operation, such as +\&\f(CW\*(C`SQRT(\-1.0)\*(C'\fR), \fBzero\fR (division by zero), \fBoverflow\fR +(overflow in a floating point operation), \fBunderflow\fR (underflow +in a floating point operation), \fBinexact\fR (loss of precision +during operation), and \fBdenormal\fR (operation performed on a +denormal value). The first five exceptions correspond to the five +\&\s-1IEEE 754\s0 exceptions, whereas the last one (\fBdenormal\fR) is not +part of the \s-1IEEE 754\s0 standard but is available on some common +architectures such as x86. +.Sp +The first three exceptions (\fBinvalid\fR, \fBzero\fR, and +\&\fBoverflow\fR) often indicate serious errors, and unless the program +has provisions for dealing with these exceptions, enabling traps for +these three exceptions is probably a good idea. +.Sp +Many, if not most, floating point operations incur loss of precision +due to rounding, and hence the \f(CW\*(C`ffpe\-trap=inexact\*(C'\fR is likely to +be uninteresting in practice. +.Sp +By default no exception traps are enabled. +.IP "\fB\-ffpe\-summary=\fR\fIlist\fR" 4 +.IX Item "-ffpe-summary=list" +Specify a list of floating-point exceptions, whose flag status is printed +to \f(CW\*(C`ERROR_UNIT\*(C'\fR when invoking \f(CW\*(C`STOP\*(C'\fR and \f(CW\*(C`ERROR STOP\*(C'\fR. +\&\fIlist\fR can be either \fBnone\fR, \fBall\fR or a comma-separated list +of the following exceptions: \fBinvalid\fR, \fBzero\fR, \fBoverflow\fR, +\&\fBunderflow\fR, \fBinexact\fR and \fBdenormal\fR. (See +\&\fB\-ffpe\-trap\fR for a description of the exceptions.) +.Sp +By default, a summary for all exceptions but \fBinexact\fR is shown. +.IP "\fB\-fno\-backtrace\fR" 4 +.IX Item "-fno-backtrace" +When a serious runtime error is encountered or a deadly signal is +emitted (segmentation fault, illegal instruction, bus error, +floating-point exception, and the other \s-1POSIX\s0 signals that have the +action \fBcore\fR), the Fortran runtime library tries to output a +backtrace of the error. \f(CW\*(C`\-fno\-backtrace\*(C'\fR disables the backtrace +generation. This option only has influence for compilation of the +Fortran main program. +.SS "Options for directory search" +.IX Subsection "Options for directory search" +These options affect how \s-1GNU\s0 Fortran searches +for files specified by the \f(CW\*(C`INCLUDE\*(C'\fR directive and where it searches +for previously compiled modules. +.PP +It also affects the search paths used by \fBcpp\fR when used to preprocess +Fortran source. +.IP "\fB\-I\fR\fIdir\fR" 4 +.IX Item "-Idir" +These affect interpretation of the \f(CW\*(C`INCLUDE\*(C'\fR directive +(as well as of the \f(CW\*(C`#include\*(C'\fR directive of the \fBcpp\fR +preprocessor). +.Sp +Also note that the general behavior of \fB\-I\fR and +\&\f(CW\*(C`INCLUDE\*(C'\fR is pretty much the same as of \fB\-I\fR with +\&\f(CW\*(C`#include\*(C'\fR in the \fBcpp\fR preprocessor, with regard to +looking for \fIheader.gcc\fR files and other such things. +.Sp +This path is also used to search for \fI.mod\fR files when previously +compiled modules are required by a \f(CW\*(C`USE\*(C'\fR statement. +.IP "\fB\-J\fR\fIdir\fR" 4 +.IX Item "-Jdir" +This option specifies where to put \fI.mod\fR files for compiled modules. +It is also added to the list of directories to searched by an \f(CW\*(C`USE\*(C'\fR +statement. +.Sp +The default is the current directory. +.IP "\fB\-fintrinsic\-modules\-path\fR \fIdir\fR" 4 +.IX Item "-fintrinsic-modules-path dir" +This option specifies the location of pre-compiled intrinsic modules, if +they are not in the default location expected by the compiler. +.SS "Influencing the linking step" +.IX Subsection "Influencing the linking step" +These options come into play when the compiler links object files into an +executable output file. They are meaningless if the compiler is not doing +a link step. +.IP "\fB\-static\-libgfortran\fR" 4 +.IX Item "-static-libgfortran" +On systems that provide \fIlibgfortran\fR as a shared and a static +library, this option forces the use of the static version. If no +shared version of \fIlibgfortran\fR was built when the compiler was +configured, this option has no effect. +.SS "Influencing runtime behavior" +.IX Subsection "Influencing runtime behavior" +These options affect the runtime behavior of programs compiled with \s-1GNU\s0 Fortran. +.IP "\fB\-fconvert=\fR\fIconversion\fR" 4 +.IX Item "-fconvert=conversion" +Specify the representation of data for unformatted files. Valid +values for conversion are: \fBnative\fR, the default; \fBswap\fR, +swap between big\- and little-endian; \fBbig-endian\fR, use big-endian +representation for unformatted files; \fBlittle-endian\fR, use little-endian +representation for unformatted files. +.Sp +\&\fIThis option has an effect only when used in the main program. +The \f(CI\*(C`CONVERT\*(C'\fI specifier and the \s-1GFORTRAN_CONVERT_UNIT\s0 environment +variable override the default specified by \f(BI\-fconvert\fI.\fR +.IP "\fB\-frecord\-marker=\fR\fIlength\fR" 4 +.IX Item "-frecord-marker=length" +Specify the length of record markers for unformatted files. +Valid values for \fIlength\fR are 4 and 8. Default is 4. +\&\fIThis is different from previous versions of\fR \fBgfortran\fR, +which specified a default record marker length of 8 on most +systems. If you want to read or write files compatible +with earlier versions of \fBgfortran\fR, use \fB\-frecord\-marker=8\fR. +.IP "\fB\-fmax\-subrecord\-length=\fR\fIlength\fR" 4 +.IX Item "-fmax-subrecord-length=length" +Specify the maximum length for a subrecord. The maximum permitted +value for length is 2147483639, which is also the default. Only +really useful for use by the gfortran testsuite. +.IP "\fB\-fsign\-zero\fR" 4 +.IX Item "-fsign-zero" +When enabled, floating point numbers of value zero with the sign bit set +are written as negative number in formatted output and treated as +negative in the \f(CW\*(C`SIGN\*(C'\fR intrinsic. \fB\-fno\-sign\-zero\fR does not +print the negative sign of zero values (or values rounded to zero for I/O) +and regards zero as positive number in the \f(CW\*(C`SIGN\*(C'\fR intrinsic for +compatibility with Fortran 77. The default is \fB\-fsign\-zero\fR. +.SS "Options for code generation conventions" +.IX Subsection "Options for code generation conventions" +These machine-independent options control the interface conventions +used in code generation. +.PP +Most of them have both positive and negative forms; the negative form +of \fB\-ffoo\fR would be \fB\-fno\-foo\fR. In the table below, only +one of the forms is listed\-\-\-the one which is not the default. You +can figure out the other form by either removing \fBno\-\fR or adding +it. +.IP "\fB\-fno\-automatic\fR" 4 +.IX Item "-fno-automatic" +Treat each program unit (except those marked as \s-1RECURSIVE\s0) as if the +\&\f(CW\*(C`SAVE\*(C'\fR statement were specified for every local variable and array +referenced in it. Does not affect common blocks. (Some Fortran compilers +provide this option under the name \fB\-static\fR or \fB\-save\fR.) +The default, which is \fB\-fautomatic\fR, uses the stack for local +variables smaller than the value given by \fB\-fmax\-stack\-var\-size\fR. +Use the option \fB\-frecursive\fR to use no static memory. +.IP "\fB\-ff2c\fR" 4 +.IX Item "-ff2c" +Generate code designed to be compatible with code generated +by \fBg77\fR and \fBf2c\fR. +.Sp +The calling conventions used by \fBg77\fR (originally implemented +in \fBf2c\fR) require functions that return type +default \f(CW\*(C`REAL\*(C'\fR to actually return the C type \f(CW\*(C`double\*(C'\fR, and +functions that return type \f(CW\*(C`COMPLEX\*(C'\fR to return the values via an +extra argument in the calling sequence that points to where to +store the return value. Under the default \s-1GNU\s0 calling conventions, such +functions simply return their results as they would in \s-1GNU\s0 +C\-\-\-default \f(CW\*(C`REAL\*(C'\fR functions return the C type \f(CW\*(C`float\*(C'\fR, and +\&\f(CW\*(C`COMPLEX\*(C'\fR functions return the \s-1GNU C\s0 type \f(CW\*(C`complex\*(C'\fR. +Additionally, this option implies the \fB\-fsecond\-underscore\fR +option, unless \fB\-fno\-second\-underscore\fR is explicitly requested. +.Sp +This does not affect the generation of code that interfaces with +the \fBlibgfortran\fR library. +.Sp +\&\fICaution:\fR It is not a good idea to mix Fortran code compiled with +\&\fB\-ff2c\fR with code compiled with the default \fB\-fno\-f2c\fR +calling conventions as, calling \f(CW\*(C`COMPLEX\*(C'\fR or default \f(CW\*(C`REAL\*(C'\fR +functions between program parts which were compiled with different +calling conventions will break at execution time. +.Sp +\&\fICaution:\fR This will break code which passes intrinsic functions +of type default \f(CW\*(C`REAL\*(C'\fR or \f(CW\*(C`COMPLEX\*(C'\fR as actual arguments, as +the library implementations use the \fB\-fno\-f2c\fR calling conventions. +.IP "\fB\-fno\-underscoring\fR" 4 +.IX Item "-fno-underscoring" +Do not transform names of entities specified in the Fortran +source file by appending underscores to them. +.Sp +With \fB\-funderscoring\fR in effect, \s-1GNU\s0 Fortran appends one +underscore to external names with no underscores. This is done to ensure +compatibility with code produced by many \s-1UNIX\s0 Fortran compilers. +.Sp +\&\fICaution\fR: The default behavior of \s-1GNU\s0 Fortran is +incompatible with \fBf2c\fR and \fBg77\fR, please use the +\&\fB\-ff2c\fR option if you want object files compiled with +\&\s-1GNU\s0 Fortran to be compatible with object code created with these +tools. +.Sp +Use of \fB\-fno\-underscoring\fR is not recommended unless you are +experimenting with issues such as integration of \s-1GNU\s0 Fortran into +existing system environments (vis\-a\*`\-vis existing libraries, tools, +and so on). +.Sp +For example, with \fB\-funderscoring\fR, and assuming other defaults like +\&\fB\-fcase\-lower\fR and that \f(CW\*(C`j()\*(C'\fR and \f(CW\*(C`max_count()\*(C'\fR are +external functions while \f(CW\*(C`my_var\*(C'\fR and \f(CW\*(C`lvar\*(C'\fR are local variables, +a statement like +.Sp +.Vb 1 +\& I = J() + MAX_COUNT (MY_VAR, LVAR) +.Ve +.Sp +is implemented as something akin to: +.Sp +.Vb 1 +\& i = j_() + max_count_\|_(&my_var_\|_, &lvar); +.Ve +.Sp +With \fB\-fno\-underscoring\fR, the same statement is implemented as: +.Sp +.Vb 1 +\& i = j() + max_count(&my_var, &lvar); +.Ve +.Sp +Use of \fB\-fno\-underscoring\fR allows direct specification of +user-defined names while debugging and when interfacing \s-1GNU\s0 Fortran +code with other languages. +.Sp +Note that just because the names match does \fInot\fR mean that the +interface implemented by \s-1GNU\s0 Fortran for an external name matches the +interface implemented by some other language for that same name. +That is, getting code produced by \s-1GNU\s0 Fortran to link to code produced +by some other compiler using this or any other method can be only a +small part of the overall solution\-\-\-getting the code generated by +both compilers to agree on issues other than naming can require +significant effort, and, unlike naming disagreements, linkers normally +cannot detect disagreements in these other areas. +.Sp +Also, note that with \fB\-fno\-underscoring\fR, the lack of appended +underscores introduces the very real possibility that a user-defined +external name will conflict with a name in a system library, which +could make finding unresolved-reference bugs quite difficult in some +cases\-\-\-they might occur at program run time, and show up only as +buggy behavior at run time. +.Sp +In future versions of \s-1GNU\s0 Fortran we hope to improve naming and linking +issues so that debugging always involves using the names as they appear +in the source, even if the names as seen by the linker are mangled to +prevent accidental linking between procedures with incompatible +interfaces. +.IP "\fB\-fsecond\-underscore\fR" 4 +.IX Item "-fsecond-underscore" +By default, \s-1GNU\s0 Fortran appends an underscore to external +names. If this option is used \s-1GNU\s0 Fortran appends two +underscores to names with underscores and one underscore to external names +with no underscores. \s-1GNU\s0 Fortran also appends two underscores to +internal names with underscores to avoid naming collisions with external +names. +.Sp +This option has no effect if \fB\-fno\-underscoring\fR is +in effect. It is implied by the \fB\-ff2c\fR option. +.Sp +Otherwise, with this option, an external name such as \f(CW\*(C`MAX_COUNT\*(C'\fR +is implemented as a reference to the link-time external symbol +\&\f(CW\*(C`max_count_\|_\*(C'\fR, instead of \f(CW\*(C`max_count_\*(C'\fR. This is required +for compatibility with \fBg77\fR and \fBf2c\fR, and is implied +by use of the \fB\-ff2c\fR option. +.IP "\fB\-fcoarray=\fR\fI\fR" 4 +.IX Item "-fcoarray=" +.RS 4 +.PD 0 +.IP "\fBnone\fR" 4 +.IX Item "none" +.PD +Disable coarray support; using coarray declarations and image-control +statements will produce a compile-time error. (Default) +.IP "\fBsingle\fR" 4 +.IX Item "single" +Single-image mode, i.e. \f(CW\*(C`num_images()\*(C'\fR is always one. +.IP "\fBlib\fR" 4 +.IX Item "lib" +Library-based coarray parallelization; a suitable \s-1GNU\s0 Fortran coarray +library needs to be linked. +.RE +.RS 4 +.RE +.IP "\fB\-fcheck=\fR\fI\fR" 4 +.IX Item "-fcheck=" +Enable the generation of run-time checks; the argument shall be +a comma-delimited list of the following keywords. +.RS 4 +.IP "\fBall\fR" 4 +.IX Item "all" +Enable all run-time test of \fB\-fcheck\fR. +.IP "\fBarray-temps\fR" 4 +.IX Item "array-temps" +Warns at run time when for passing an actual argument a temporary array +had to be generated. The information generated by this warning is +sometimes useful in optimization, in order to avoid such temporaries. +.Sp +Note: The warning is only printed once per location. +.IP "\fBbounds\fR" 4 +.IX Item "bounds" +Enable generation of run-time checks for array subscripts +and against the declared minimum and maximum values. It also +checks array indices for assumed and deferred +shape arrays against the actual allocated bounds and ensures that all string +lengths are equal for character array constructors without an explicit +typespec. +.Sp +Some checks require that \fB\-fcheck=bounds\fR is set for +the compilation of the main program. +.Sp +Note: In the future this may also include other forms of checking, e.g., +checking substring references. +.IP "\fBdo\fR" 4 +.IX Item "do" +Enable generation of run-time checks for invalid modification of loop +iteration variables. +.IP "\fBmem\fR" 4 +.IX Item "mem" +Enable generation of run-time checks for memory allocation. +Note: This option does not affect explicit allocations using the +\&\f(CW\*(C`ALLOCATE\*(C'\fR statement, which will be always checked. +.IP "\fBpointer\fR" 4 +.IX Item "pointer" +Enable generation of run-time checks for pointers and allocatables. +.IP "\fBrecursion\fR" 4 +.IX Item "recursion" +Enable generation of run-time checks for recursively called subroutines and +functions which are not marked as recursive. See also \fB\-frecursive\fR. +Note: This check does not work for OpenMP programs and is disabled if used +together with \fB\-frecursive\fR and \fB\-fopenmp\fR. +.RE +.RS 4 +.RE +.IP "\fB\-fbounds\-check\fR" 4 +.IX Item "-fbounds-check" +Deprecated alias for \fB\-fcheck=bounds\fR. +.IP "\fB\-fcheck\-array\-temporaries\fR" 4 +.IX Item "-fcheck-array-temporaries" +Deprecated alias for \fB\-fcheck=array\-temps\fR. +.IP "\fB\-fmax\-array\-constructor=\fR\fIn\fR" 4 +.IX Item "-fmax-array-constructor=n" +This option can be used to increase the upper limit permitted in +array constructors. The code below requires this option to expand +the array at compile time. +.Sp +.Vb 7 +\& program test +\& implicit none +\& integer j +\& integer, parameter :: n = 100000 +\& integer, parameter :: i(n) = (/ (2*j, j = 1, n) /) +\& print \*(Aq(10(I0,1X))\*(Aq, i +\& end program test +.Ve +.Sp +\&\fICaution: This option can lead to long compile times and excessively +large object files.\fR +.Sp +The default value for \fIn\fR is 65535. +.IP "\fB\-fmax\-stack\-var\-size=\fR\fIn\fR" 4 +.IX Item "-fmax-stack-var-size=n" +This option specifies the size in bytes of the largest array that will be put +on the stack; if the size is exceeded static memory is used (except in +procedures marked as \s-1RECURSIVE\s0). Use the option \fB\-frecursive\fR to +allow for recursive procedures which do not have a \s-1RECURSIVE\s0 attribute or +for parallel programs. Use \fB\-fno\-automatic\fR to never use the stack. +.Sp +This option currently only affects local arrays declared with constant +bounds, and may not apply to all character variables. +Future versions of \s-1GNU\s0 Fortran may improve this behavior. +.Sp +The default value for \fIn\fR is 32768. +.IP "\fB\-fstack\-arrays\fR" 4 +.IX Item "-fstack-arrays" +Adding this option will make the Fortran compiler put all local arrays, +even those of unknown size onto stack memory. If your program uses very +large local arrays it is possible that you will have to extend your runtime +limits for stack memory on some operating systems. This flag is enabled +by default at optimization level \fB\-Ofast\fR. +.IP "\fB\-fpack\-derived\fR" 4 +.IX Item "-fpack-derived" +This option tells \s-1GNU\s0 Fortran to pack derived type members as closely as +possible. Code compiled with this option is likely to be incompatible +with code compiled without this option, and may execute slower. +.IP "\fB\-frepack\-arrays\fR" 4 +.IX Item "-frepack-arrays" +In some circumstances \s-1GNU\s0 Fortran may pass assumed shape array +sections via a descriptor describing a noncontiguous area of memory. +This option adds code to the function prologue to repack the data into +a contiguous block at runtime. +.Sp +This should result in faster accesses to the array. However it can introduce +significant overhead to the function call, especially when the passed data +is noncontiguous. +.IP "\fB\-fshort\-enums\fR" 4 +.IX Item "-fshort-enums" +This option is provided for interoperability with C code that was +compiled with the \fB\-fshort\-enums\fR option. It will make +\&\s-1GNU\s0 Fortran choose the smallest \f(CW\*(C`INTEGER\*(C'\fR kind a given +enumerator set will fit in, and give all its enumerators this kind. +.IP "\fB\-fexternal\-blas\fR" 4 +.IX Item "-fexternal-blas" +This option will make \fBgfortran\fR generate calls to \s-1BLAS\s0 functions +for some matrix operations like \f(CW\*(C`MATMUL\*(C'\fR, instead of using our own +algorithms, if the size of the matrices involved is larger than a given +limit (see \fB\-fblas\-matmul\-limit\fR). This may be profitable if an +optimized vendor \s-1BLAS\s0 library is available. The \s-1BLAS\s0 library will have +to be specified at link time. +.IP "\fB\-fblas\-matmul\-limit=\fR\fIn\fR" 4 +.IX Item "-fblas-matmul-limit=n" +Only significant when \fB\-fexternal\-blas\fR is in effect. +Matrix multiplication of matrices with size larger than (or equal to) \fIn\fR +will be performed by calls to \s-1BLAS\s0 functions, while others will be +handled by \fBgfortran\fR internal algorithms. If the matrices +involved are not square, the size comparison is performed using the +geometric mean of the dimensions of the argument and result matrices. +.Sp +The default value for \fIn\fR is 30. +.IP "\fB\-frecursive\fR" 4 +.IX Item "-frecursive" +Allow indirect recursion by forcing all local arrays to be allocated +on the stack. This flag cannot be used together with +\&\fB\-fmax\-stack\-var\-size=\fR or \fB\-fno\-automatic\fR. +.IP "\fB\-finit\-local\-zero\fR" 4 +.IX Item "-finit-local-zero" +.PD 0 +.IP "\fB\-finit\-integer=\fR\fIn\fR" 4 +.IX Item "-finit-integer=n" +.IP "\fB\-finit\-real=\fR\fI\fR" 4 +.IX Item "-finit-real=" +.IP "\fB\-finit\-logical=\fR\fI\fR" 4 +.IX Item "-finit-logical=" +.IP "\fB\-finit\-character=\fR\fIn\fR" 4 +.IX Item "-finit-character=n" +.PD +The \fB\-finit\-local\-zero\fR option instructs the compiler to +initialize local \f(CW\*(C`INTEGER\*(C'\fR, \f(CW\*(C`REAL\*(C'\fR, and \f(CW\*(C`COMPLEX\*(C'\fR +variables to zero, \f(CW\*(C`LOGICAL\*(C'\fR variables to false, and +\&\f(CW\*(C`CHARACTER\*(C'\fR variables to a string of null bytes. Finer-grained +initialization options are provided by the +\&\fB\-finit\-integer=\fR\fIn\fR, +\&\fB\-finit\-real=\fR\fI\fR (which also initializes +the real and imaginary parts of local \f(CW\*(C`COMPLEX\*(C'\fR variables), +\&\fB\-finit\-logical=\fR\fI\fR, and +\&\fB\-finit\-character=\fR\fIn\fR (where \fIn\fR is an \s-1ASCII\s0 character +value) options. These options do not initialize +.RS 4 +.IP "\(bu" 4 +allocatable arrays +.IP "\(bu" 4 +components of derived type variables +.IP "\(bu" 4 +variables that appear in an \f(CW\*(C`EQUIVALENCE\*(C'\fR statement. +.RE +.RS 4 +.Sp +(These limitations may be removed in future releases). +.Sp +Note that the \fB\-finit\-real=nan\fR option initializes \f(CW\*(C`REAL\*(C'\fR +and \f(CW\*(C`COMPLEX\*(C'\fR variables with a quiet NaN. For a signalling NaN +use \fB\-finit\-real=snan\fR; note, however, that compile-time +optimizations may convert them into quiet NaN and that trapping +needs to be enabled (e.g. via \fB\-ffpe\-trap\fR). +.Sp +Finally, note that enabling any of the \fB\-finit\-*\fR options will +silence warnings that would have been emitted by \fB\-Wuninitialized\fR +for the affected local variables. +.RE +.IP "\fB\-falign\-commons\fR" 4 +.IX Item "-falign-commons" +By default, \fBgfortran\fR enforces proper alignment of all variables in a +\&\f(CW\*(C`COMMON\*(C'\fR block by padding them as needed. On certain platforms this is mandatory, +on others it increases performance. If a \f(CW\*(C`COMMON\*(C'\fR block is not declared with +consistent data types everywhere, this padding can cause trouble, and +\&\fB\-fno\-align\-commons\fR can be used to disable automatic alignment. The +same form of this option should be used for all files that share a \f(CW\*(C`COMMON\*(C'\fR block. +To avoid potential alignment issues in \f(CW\*(C`COMMON\*(C'\fR blocks, it is recommended to order +objects from largest to smallest. +.IP "\fB\-fno\-protect\-parens\fR" 4 +.IX Item "-fno-protect-parens" +By default the parentheses in expression are honored for all optimization +levels such that the compiler does not do any re-association. Using +\&\fB\-fno\-protect\-parens\fR allows the compiler to reorder \f(CW\*(C`REAL\*(C'\fR and +\&\f(CW\*(C`COMPLEX\*(C'\fR expressions to produce faster code. Note that for the re-association +optimization \fB\-fno\-signed\-zeros\fR and \fB\-fno\-trapping\-math\fR +need to be in effect. The parentheses protection is enabled by default, unless +\&\fB\-Ofast\fR is given. +.IP "\fB\-frealloc\-lhs\fR" 4 +.IX Item "-frealloc-lhs" +An allocatable left-hand side of an intrinsic assignment is automatically +(re)allocated if it is either unallocated or has a different shape. The +option is enabled by default except when \fB\-std=f95\fR is given. See +also \fB\-Wrealloc\-lhs\fR. +.IP "\fB\-faggressive\-function\-elimination\fR" 4 +.IX Item "-faggressive-function-elimination" +Functions with identical argument lists are eliminated within +statements, regardless of whether these functions are marked +\&\f(CW\*(C`PURE\*(C'\fR or not. For example, in +.Sp +.Vb 1 +\& a = f(b,c) + f(b,c) +.Ve +.Sp +there will only be a single call to \f(CW\*(C`f\*(C'\fR. This option only works +if \fB\-ffrontend\-optimize\fR is in effect. +.IP "\fB\-ffrontend\-optimize\fR" 4 +.IX Item "-ffrontend-optimize" +This option performs front-end optimization, based on manipulating +parts the Fortran parse tree. Enabled by default by any \fB\-O\fR +option. Optimizations enabled by this option include elimination of +identical function calls within expressions, removing unnecessary +calls to \f(CW\*(C`TRIM\*(C'\fR in comparisons and assignments and replacing +\&\f(CWTRIM(a)\fR with \f(CW\*(C`a(1:LEN_TRIM(a))\*(C'\fR. +It can be deselected by specifying \fB\-fno\-frontend\-optimize\fR. +.SH "ENVIRONMENT" +.IX Header "ENVIRONMENT" +The \fBgfortran\fR compiler currently does not make use of any environment +variables to control its operation above and beyond those +that affect the operation of \fBgcc\fR. +.SH "BUGS" +.IX Header "BUGS" +For instructions on reporting bugs, see +<\fBhttp://gcc.gnu.org/bugs.html\fR>. +.SH "SEE ALSO" +.IX Header "SEE ALSO" +\&\fIgpl\fR\|(7), \fIgfdl\fR\|(7), \fIfsf\-funding\fR\|(7), +\&\fIcpp\fR\|(1), \fIgcov\fR\|(1), \fIgcc\fR\|(1), \fIas\fR\|(1), \fIld\fR\|(1), \fIgdb\fR\|(1), \fIadb\fR\|(1), \fIdbx\fR\|(1), \fIsdb\fR\|(1) +and the Info entries for \fIgcc\fR, \fIcpp\fR, \fIgfortran\fR, \fIas\fR, +\&\fIld\fR, \fIbinutils\fR and \fIgdb\fR. +.SH "AUTHOR" +.IX Header "AUTHOR" +See the Info entry for \fBgfortran\fR for contributors to \s-1GCC\s0 and +\&\s-1GNU\s0 Fortran. +.SH "COPYRIGHT" +.IX Header "COPYRIGHT" +Copyright (c) 2004\-2014 Free Software Foundation, Inc. +.PP +Permission is granted to copy, distribute and/or modify this document +under the terms of the \s-1GNU\s0 Free Documentation License, Version 1.3 or +any later version published by the Free Software Foundation; with the +Invariant Sections being \*(L"Funding Free Software\*(R", 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 \fIgfdl\fR\|(7) man page. +.PP +(a) The \s-1FSF\s0's Front-Cover Text is: +.PP +.Vb 1 +\& A GNU Manual +.Ve +.PP +(b) The \s-1FSF\s0's Back-Cover Text is: +.PP +.Vb 3 +\& 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. +.Ve -- cgit v1.2.3