@c Copyright (c) 1999, 2000, 2001, 2002, 2004@c Free Software Foundation, Inc.@c This is part of the CPP and GCC manuals.@c For copying conditions, see the file gcc.texi.@c ---------------------------------------------------------------------@c Environment variables affecting the preprocessor@c ---------------------------------------------------------------------@c If this file is included with the flag ``cppmanual'' set, it is@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.@vtable @env@item CPATH@itemx C_INCLUDE_PATH@itemx CPLUS_INCLUDE_PATH@itemx OBJC_INCLUDE_PATH@c Commented out until ObjC++ is part of GCC:@c @itemx OBJCPLUS_INCLUDE_PATHEach variable's value is a list of directories separated by a specialcharacter, much like @env{PATH}, in which to look for header files.The special character, @code{PATH_SEPARATOR}, is target-dependent anddetermined at GCC build time.  For Microsoft Windows-based targets it is asemicolon, and for almost all other targets it is a colon.@env{CPATH} specifies a list of directories to be searched as ifspecified with @option{-I}, but after any paths given with @option{-I}options on the command line.  This environment variable is usedregardless of which language is being preprocessed.The remaining environment variables apply only when preprocessing theparticular language indicated.  Each specifies a list of directoriesto be searched as if specified with @option{-isystem}, but after anypaths given with @option{-isystem} options on the command line.In all these variables, an empty element instructs the compiler tosearch its current working directory.  Empty elements can appear at thebeginning or end of a path.  For instance, if the value of@env{CPATH} is @code{:/special/include}, that has the sameeffect as @samp{@w{-I. -I/special/include}}.@c man end@ifset cppmanualSee also @ref{Search Path}.@end ifset@c man begin ENVIRONMENT@item DEPENDENCIES_OUTPUT@cindex dependencies for make as outputIf this variable is set, its value specifies how to outputdependencies for Make based on the non-system header files processedby the compiler.  System header files are ignored in the dependencyoutput.The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, inwhich case the Make rules are written to that file, guessing the targetname from the source file name.  Or the value can have the form@samp{@var{file} @var{target}}, in which case the rules are written tofile @var{file} using @var{target} as the target name.In other words, this environment variable is equivalent to combiningthe options @option{-MM} and @option{-MF}@ifset cppmanual(@pxref{Invocation}),@end ifset@ifclear cppmanual(@pxref{Preprocessor Options}),@end ifclearwith an optional @option{-MT} switch too.@item SUNPRO_DEPENDENCIES@cindex dependencies for make as outputThis variable is the same as @env{DEPENDENCIES_OUTPUT} (see above),except that system header files are not ignored, so it implies@option{-M} rather than @option{-MM}.  However, the dependence on themain input file is omitted.@ifset cppmanual@xref{Invocation}.@end ifset@ifclear cppmanual@xref{Preprocessor Options}.@end ifclear@end vtable