1@c Copyright (c) 1999, 2000, 2001, 2002, 2004
2@c Free Software Foundation, Inc.
3@c This is part of the CPP and GCC manuals.
4@c For copying conditions, see the file gcc.texi.
5
6@c ---------------------------------------------------------------------
7@c Environment variables affecting the preprocessor
8@c ---------------------------------------------------------------------
9
10@c If this file is included with the flag ``cppmanual'' set, it is
11@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.
12
13@vtable @env
14@item CPATH
15@itemx C_INCLUDE_PATH
16@itemx CPLUS_INCLUDE_PATH
17Each variable's value is a list of directories separated by a special
18character, much like @env{PATH}, in which to look for header files.
19The special character, @code{PATH_SEPARATOR}, is target-dependent and
20determined at GCC build time.  For Microsoft Windows-based targets it is a
21semicolon, and for almost all other targets it is a colon.
22
23@env{CPATH} specifies a list of directories to be searched as if
24specified with @option{-I}, but after any paths given with @option{-I}
25options on the command line.  This environment variable is used
26regardless of which language is being preprocessed.
27
28The remaining environment variables apply only when preprocessing the
29particular language indicated.  Each specifies a list of directories
30to be searched as if specified with @option{-isystem}, but after any
31paths given with @option{-isystem} options on the command line.
32
33In all these variables, an empty element instructs the compiler to
34search its current working directory.  Empty elements can appear at the
35beginning or end of a path.  For instance, if the value of
36@env{CPATH} is @code{:/special/include}, that has the same
37effect as @samp{@w{-I. -I/special/include}}.
38
39@c man end
40@ifset cppmanual
41See also @ref{Search Path}.
42@end ifset
43@c man begin ENVIRONMENT
44
45@item DEPENDENCIES_OUTPUT
46@cindex dependencies for make as output
47If this variable is set, its value specifies how to output
48dependencies for Make based on the non-system header files processed
49by the compiler.  System header files are ignored in the dependency
50output.
51
52The value of @env{DEPENDENCIES_OUTPUT} can be just a file name, in
53which case the Make rules are written to that file, guessing the target
54name from the source file name.  Or the value can have the form
55@samp{@var{file} @var{target}}, in which case the rules are written to
56file @var{file} using @var{target} as the target name.
57
58In other words, this environment variable is equivalent to combining
59the options @option{-MM} and @option{-MF}
60@ifset cppmanual
61(@pxref{Invocation}),
62@end ifset
63@ifclear cppmanual
64(@pxref{Preprocessor Options}),
65@end ifclear
66with an optional @option{-MT} switch too.
67
68@item SUNPRO_DEPENDENCIES
69@cindex dependencies for make as output
70This variable is the same as @env{DEPENDENCIES_OUTPUT} (see above),
71except that system header files are not ignored, so it implies
72@option{-M} rather than @option{-MM}.  However, the dependence on the
73main input file is omitted.
74@ifset cppmanual
75@xref{Invocation}.
76@end ifset
77@ifclear cppmanual
78@xref{Preprocessor Options}.
79@end ifclear
80@end vtable
81