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+# checksrc
+
+This is the tool we use within the curl project to scan C source code and
+check that it adheres to our [Source Code Style guide](CODE_STYLE.md).
+
+## Usage
+
+    checksrc.pl [options] [file1] [file2] ...
+
+## Command line options
+
+`-W[file]` whitelists that file and excludes it from being checked. Helpful
+when, for example, one of the files is generated.
+
+`-D[dir]` directory name to prepend to file names when accessing them.
+
+`-h` shows the help output, that also lists all recognized warnings
+
+## What does checksrc warn for?
+
+checksrc does not check and verify the code against the entire style guide,
+but the script is instead an effort to detect the most common mistakes and
+syntax mistakes that contributers make before they get accustomed to our code
+style. Heck, many of us regulars do the mistakes too and this script helps us
+keep the code in shape.
+
+    checksrc.pl -h
+
+Lists how to use the script and it lists all existing warnings it has and
+problems it detects. At the time of this writing, the existing checksrc
+warnings are:
+
+- `BADCOMMAND`: There's a bad !checksrc! instruction in the code. See the
+   **Ignore certain warnings** section below for details.
+
+- `BANNEDFUNC`: A banned function was used. The funtions sprintf, vsprintf,
+   strcat, strncat, gets are **never** allowed in curl source code.
+
+- `BRACEELSE`: '} else' on the same line. The else is supposed to be on the
+  following line.
+
+- `BRACEPOS`: wrong position for an open brace (`{`).
+
+- `COMMANOSPACE`: a comma without following space
+
+- `COPYRIGHT`: the file is missing a copyright statement!
+
+- `CPPCOMMENTS`: `//` comment detected, that's not C89 compliant
+
+- `FOPENMODE`: `fopen()` needs a macro for the mode string, use it
+
+- `INDENTATION`: detected a wrong start column for code. Note that this warning
+   only checks some specific places and will certainly miss many bad
+   indentations.
+
+- `LONGLINE`: A line is longer than 79 columns.
+
+- `PARENBRACE`: `){` was used without sufficient space in between.
+
+- `RETURNNOSPACE`: `return` was used without space between the keyword and the
+   following value.
+
+- `SPACEAFTERPAREN`: there was a space after open parenthesis, `( text`.
+
+- `SPACEBEFORECLOSE`: there was a space before a close parenthesis, `text )`.
+
+- `SPACEBEFORECOMMA`: there was a space before a comma, `one , two`.
+
+- `SPACEBEFOREPAREN`: there was a space before an open parenthesis, `if (`,
+   where one was not expected
+
+- `SPACESEMILCOLON`: there was a space before semicolon, ` ;`.
+
+- `TABS`: TAB characters are not allowed!
+
+- `TRAILINGSPACE`: Trailing white space on the line
+
+- `UNUSEDIGNORE`: a checksrc inlined warning ignore was asked for but not used,
+   that's an ignore that should be removed or changed to get used.
+
+## Ignore certain warnings
+
+Due to the nature of the source code and the flaws of the checksrc tool, there
+is sometimes a need to ignore specific warnings. checksrc allows a few
+different ways to do this.
+
+### Inline ignore
+
+You can control what to ignore within a specific source file by providing
+instructions to checksrc in the source code itself. You need a magic marker
+that is `!checksrc!` followed by the instruction. The instruction can ask to
+ignore a specific warning N number of times or you ignore all of them until
+you mark the end of the ignored section.
+
+Inline ignores are only done for that single specific source code file.
+
+Example
+
+    /* !checksrc! disable LONGLINE all */
+
+This will ignore the warning for overly long lines until it is re-enabled with:
+
+    /* !checksrc! enable LONGLINE */
+
+If the enabling isn't performed before the end of the file, it will be enabled
+automatically for the next file.
+
+You can also opt to ignore just N violations so that if you have a single long
+line you just can't shorten and is agreed to be fine anyway:
+
+    /* !checksrc! disable LONGLINE 1 */
+
+... and the warning for long lines will be enabled again automatically after
+it has ignored that single warning. The number `1` can of course be changed to
+any other integer number. It can be used to make sure only the exact intended
+instances are ignored and nothing extra.
+
+### Directory wide ignore patterns
+
+This is a method we've transitioned away from. Use inline ignores as far as
+possible.
+
+Make a `checksrc.whitelist` file in the directory of the source code with the
+false positive, and include the full offending line into this file.