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97 lines
3.5 KiB
ReStructuredText
97 lines
3.5 KiB
ReStructuredText
..
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Copyright 1988-2022 Free Software Foundation, Inc.
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This is part of the GCC manual.
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For copying conditions, see the copyright.rst file.
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.. envvar:: CPATH, C_INCLUDE_PATH, CPLUS_INCLUDE_PATH, OBJC_INCLUDE_PATH
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.. Commented out until ObjC++ is part of GCC:
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@itemx OBJCPLUS_INCLUDE_PATH
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Each variable's value is a list of directories separated by a special
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character, much like :envvar:`PATH`, in which to look for header files.
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The special character, ``PATH_SEPARATOR``, is target-dependent and
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determined at GCC build time. For Microsoft Windows-based targets it is a
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semicolon, and for almost all other targets it is a colon.
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:envvar:`CPATH` specifies a list of directories to be searched as if
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specified with :option:`-I`, but after any paths given with :option:`-I`
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options on the command line. This environment variable is used
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regardless of which language is being preprocessed.
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The remaining environment variables apply only when preprocessing the
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particular language indicated. Each specifies a list of directories
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to be searched as if specified with :option:`-isystem`, but after any
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paths given with :option:`-isystem` options on the command line.
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In all these variables, an empty element instructs the compiler to
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search its current working directory. Empty elements can appear at the
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beginning or end of a path. For instance, if the value of
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:envvar:`CPATH` is ``:/special/include``, that has the same
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effect as :samp:`-I. -I/special/include`.
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.. only:: cpp
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See also :ref:`search-path`.
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.. index:: dependencies for make as output
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.. envvar:: DEPENDENCIES_OUTPUT
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If this variable is set, its value specifies how to output
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dependencies for Make based on the non-system header files processed
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by the compiler. System header files are ignored in the dependency
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output.
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The value of :envvar:`DEPENDENCIES_OUTPUT` can be just a file name, in
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which case the Make rules are written to that file, guessing the target
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name from the source file name. Or the value can have the form
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:samp:`{file}{target}`, in which case the rules are written to
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file :samp:`{file}` using :samp:`{target}` as the target name.
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In other words, this environment variable is equivalent to combining
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the options :option:`-MM` and :option:`-MF`
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.. only:: cpp
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(see :ref:`invocation`),
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.. only:: not cpp
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(see :ref:`preprocessor-options`),
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with an optional :option:`-MT` switch too.
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.. index:: dependencies for make as output
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.. envvar:: SUNPRO_DEPENDENCIES
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This variable is the same as :envvar:`DEPENDENCIES_OUTPUT` (see above),
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except that system header files are not ignored, so it implies
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:option:`-M` rather than :option:`-MM`. However, the dependence on the
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main input file is omitted.
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.. only:: cpp
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See :ref:`invocation`.
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.. only:: not cpp
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See :ref:`preprocessor-options`.
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.. envvar:: SOURCE_DATE_EPOCH
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If this variable is set, its value specifies a UNIX timestamp to be
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used in replacement of the current date and time in the ``__DATE__``
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and ``__TIME__`` macros, so that the embedded timestamps become
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reproducible.
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The value of :envvar:`SOURCE_DATE_EPOCH` must be a UNIX timestamp,
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defined as the number of seconds (excluding leap seconds) since
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01 Jan 1970 00:00:00 represented in ASCII; identical to the output of
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``date +%s`` on GNU/Linux and other systems that support the
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``%s`` extension in the ``date`` command.
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The value should be a known timestamp such as the last modification
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time of the source or package and it should be set by the build
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process. |