-@c Copyright (c) 1999, 2000, 2001, 2002
+@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
@c Free Software Foundation, Inc.
@c This is part of the CPP and GCC manuals.
@c For copying conditions, see the file gcc.texi.
Predefine @var{name} as a macro, with definition @code{1}.
@item -D @var{name}=@var{definition}
-Predefine @var{name} as a macro, with definition @var{definition}.
-There are no restrictions on the contents of @var{definition}, but 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.
+The contents of @var{definition} are tokenized and processed as if
+they appeared during translation phase three in a @samp{#define}
+directive. In particular, the definition will be truncated by
+embedded newline characters.
+
+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.
If you wish to define a function-like macro on the command line, write
its argument list with surrounding parentheses before the equals sign
@item -undef
@opindex undef
-Do not predefine any system-specific macros. The common predefined
-macros remain defined.
+Do not predefine any system-specific or GCC-specific macros. The
+standard predefined macros remain defined.
+@ifset cppmanual
+@xref{Standard Predefined Macros}.
+@end ifset
@item -I @var{dir}
@opindex I
@xref{Search Path}.
@end ifset
Directories named by @option{-I} are searched before the standard
-system include directories.
-
-It is dangerous to specify a standard system include directory in an
-@option{-I} option. This defeats the special treatment of system
-headers
+system include directories. If the directory @var{dir} is a standard
+system include directory, the option is ignored to ensure that the
+default search order for system directories and the special treatment
+of system headers are not defeated
@ifset cppmanual
(@pxref{System Headers})
@end ifset
-. It can also defeat the repairs to buggy system headers which GCC
-makes when it is installed.
+.
+If @var{dir} begins with @code{=}, then the @code{=} will be replaced
+by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
@item -o @var{file}
@opindex o
@item -Wall
@opindex Wall
-Turns on all optional warnings which are desirable for normal code. At
-present this is @option{-Wcomment} and @option{-Wtrigraphs}. Note that
-many of the preprocessor's warnings are on by default and have no
-options to control them.
+Turns on all optional warnings which are desirable for normal code.
+At present this is @option{-Wcomment}, @option{-Wtrigraphs},
+@option{-Wmultichar} and a warning about integer promotion causing a
+change of sign in @code{#if} expressions. Note that many of the
+preprocessor's warnings are on by default and have no options to
+control them.
@item -Wcomment
@itemx -Wcomments
@item -Wtrigraphs
@opindex Wtrigraphs
-Warn if any trigraphs are encountered. This option used to take effect
-only if @option{-trigraphs} was also specified, but now works
-independently. Warnings are not given for trigraphs within comments, as
-they do not affect the meaning of the program.
+@anchor{Wtrigraphs}
+Most trigraphs in comments cannot affect the meaning of the program.
+However, a trigraph that would form an escaped newline (@samp{??/} at
+the end of a line) can, by changing where the comment begins or ends.
+Therefore, only trigraphs that would form escaped newlines produce
+warnings inside a comment.
+
+This option is implied by @option{-Wall}. If @option{-Wall} is not
+given, this option is still enabled unless trigraphs are enabled. To
+get trigraph conversion without warnings, but get the other
+@option{-Wall} warnings, use @samp{-trigraphs -Wall -Wno-trigraphs}.
@item -Wtraditional
@opindex Wtraditional
@xref{Traditional Mode}.
@end ifset
-@item -Wimport
-@opindex Wimport
-Warn the first time @samp{#import} is used.
-
@item -Wundef
@opindex Wundef
Warn whenever an identifier which is not a macro is encountered in an
@samp{#if} directive, outside of @samp{defined}. Such identifiers are
replaced with zero.
+@item -Wunused-macros
+@opindex Wunused-macros
+Warn about macros defined in the main file that are unused. A macro
+is @dfn{used} if it is expanded or tested for existence at least once.
+The preprocessor will also warn if the macro has not been used at the
+time it is redefined or undefined.
+
+Built-in macros, macros defined on the command line, and macros
+defined in include files are not warned about.
+
+@emph{Note:} If a macro is actually used, but only used in skipped
+conditional blocks, then CPP will report it as unused. To avoid the
+warning in such a case, you might improve the scope of the macro's
+definition by, for example, moving it into the first skipped block.
+Alternatively, you could provide a dummy use with something like:
+
+@smallexample
+#if defined the_macro_causing_the_warning
+#endif
+@end smallexample
+
+@item -Wendif-labels
+@opindex Wendif-labels
+Warn whenever an @samp{#else} or an @samp{#endif} are followed by text.
+This usually happens in code of the form
+
+@smallexample
+#if FOO
+@dots{}
+#else FOO
+@dots{}
+#endif FOO
+@end smallexample
+
+@noindent
+The second and third @code{FOO} should be in comments, but often are not
+in older programs. This warning is on by default.
+
@item -Werror
@opindex Werror
Make all warnings into hard errors. Source code which triggers warnings
@option{-imacros} command line options.
Unless specified explicitly (with @option{-MT} or @option{-MQ}), the
-object file name consists of the basename of the source file with any
-suffix replaced with object file suffix. If there are many included
-files then the rule is split into several lines using @samp{\}-newline.
-The rule has no commands.
+object file name consists of the name of the source file with any
+suffix replaced with object file suffix and with any leading directory
+parts removed. If there are many included files then the rule is
+split into several lines using @samp{\}-newline. The rule has no
+commands.
This option does not suppress the preprocessor's debug output, such as
@option{-dM}. To avoid mixing such debug output with the dependency
rules you should explicitly specify the dependency output file with
@option{-MF}, or use an environment variable like
-@env{DEPENDENCIES_OUTPUT} (@pxref{DEPENDENCIES_OUTPUT}). Debug output
+@env{DEPENDENCIES_OUTPUT} (@pxref{Environment Variables}). Debug output
will still be sent to the regular output stream as normal.
-Passing @option{-M} to the driver implies @option{-E}.
+Passing @option{-M} to the driver implies @option{-E}, and suppresses
+warnings with an implicit @option{-w}.
@item -MM
@opindex MM
header will appear in @option{-MM} dependency output. This is a
slight change in semantics from GCC versions 3.0 and earlier.
+@anchor{dashMF}
@item -MF @var{file}
@opindex MF
-@anchor{-MF}
When used with @option{-M} or @option{-MM}, specifies a
file to write the dependencies to. If no @option{-MF} switch is given
the preprocessor sends the rules to the same place it would have sent
@item -MG
@opindex MG
-When used with @option{-M} or @option{-MM}, @option{-MG} says to treat missing
-header files as generated files and assume they live in the same
-directory as the source file. It suppresses preprocessed output, as a
-missing header file is ordinarily an error.
+In conjunction with an option such as @option{-M} requesting
+dependency generation, @option{-MG} assumes missing header files are
+generated files and adds them to the dependency list without raising
+an error. The dependency filename is taken directly from the
+@code{#include} directive without prepending any path. @option{-MG}
+also suppresses preprocessed output, as a missing header file renders
+this useless.
This feature is used in automatic updating of makefiles.
This is typical output:
-@example
+@smallexample
test.o: test.c test.h
test.h:
-@end example
+@end smallexample
@item -MT @var{target}
@opindex MT
Change the target of the rule emitted by dependency generation. By
-default CPP takes the name of the main input file, including any path,
-deletes any file suffix such as @samp{.c}, and appends the platform's
-usual object suffix. The result is the target.
+default CPP takes the name of the main input file, deletes any
+directory components and any file suffix such as @samp{.c}, and
+appends the platform's usual object suffix. The result is the target.
An @option{-MT} option will set the target to be exactly the string you
specify. If you want multiple targets, you can specify them as a single
For example, @option{@w{-MT '$(objpfx)foo.o'}} might give
-@example
+@smallexample
$(objpfx)foo.o: foo.c
-@end example
+@end smallexample
@item -MQ @var{target}
@opindex MQ
Same as @option{-MT}, but it quotes any characters which are special to
Make. @option{@w{-MQ '$(objpfx)foo.o'}} gives
-@example
+@smallexample
$$(objpfx)foo.o: foo.c
-@end example
+@end smallexample
The default target is automatically quoted, as if it were given with
@option{-MQ}.
@option{-MD} is equivalent to @option{-M -MF @var{file}}, except that
@option{-E} is not implied. The driver determines @var{file} based on
whether an @option{-o} option is given. If it is, the driver uses its
-argument but with a suffix of @file{.d}, otherwise it take the
-basename of the input file and applies a @file{.d} suffix.
+argument but with a suffix of @file{.d}, otherwise it takes the name
+of the input file, removes any directory components and suffix, and
+applies a @file{.d} suffix.
If @option{-MD} is used in conjunction with @option{-E}, any
@option{-o} switch is understood to specify the dependency output file
-(but @pxref{-MF}), but if used without @option{-E}, each @option{-o}
+(@pxref{dashMF,,-MF}), but if used without @option{-E}, each @option{-o}
is understood to specify a target object file.
Since @option{-E} is not implied, @option{-MD} can be used to generate
@item -MMD
@opindex MMD
Like @option{-MD} except mention only user header files, not system
--header files.
+header files.
+@ifclear cppmanual
+@item -fpch-deps
+@opindex fpch-deps
+When using precompiled headers (@pxref{Precompiled Headers}), this flag
+will cause the dependency-output flags to also list the files from the
+precompiled header's dependencies. If not specified only the
+precompiled header would be listed and not the files that were used to
+create it because those files are not consulted when a precompiled
+header is used.
+
+@item -fpch-preprocess
+@opindex fpch-preprocess
+This option allows use of a precompiled header (@pxref{Precompiled
+Headers}) together with @option{-E}. It inserts a special @code{#pragma},
+@code{#pragma GCC pch_preprocess "<filename>"} in the output to mark
+the place where the precompiled header was found, and its filename. When
+@option{-fpreprocessed} is in use, GCC recognizes this @code{#pragma} and
+loads the PCH@.
+
+This option is off by default, because the resulting preprocessed output
+is only really suitable as input to GCC@. It is switched on by
+@option{-save-temps}.
+
+You should not write this @code{#pragma} in your own code, but it is
+safe to edit the filename if the PCH file is available in a different
+location. The filename may be absolute or it may be relative to GCC's
+current directory.
+
+@end ifclear
@item -x c
@itemx -x c++
@itemx -x objective-c
recognize the extension, it will treat the file as C; this is the most
generic mode.
-@strong{Note:} Previous versions of cpp accepted a @option{-lang} option
+@emph{Note:} Previous versions of cpp accepted a @option{-lang} option
which selected both the language and the standards conformance level.
This option has been removed, because it conflicts with the @option{-l}
option.
@itemx -ansi
@opindex ansi
@opindex std=
-Specify the standard to which the code should conform. Currently cpp
-only knows about the standards for C; other language standards will be
-added in the future.
+Specify the standard to which the code should conform. Currently CPP
+knows about C and C++ standards; others may be added in the future.
@var{standard}
may be one of:
@item gnu99
@itemx gnu9x
The 1999 C standard plus GNU extensions.
+
+@item c++98
+The 1998 ISO C++ standard plus amendments.
+
+@item gnu++98
+The same as @option{-std=c++98} plus GNU extensions. This is the
+default for C++ code.
@end table
@item -I-
@ifset cppmanual
@xref{Search Path}.
@end ifset
+This option has been deprecated.
@item -nostdinc
@opindex nostdinc
Search @var{dir} for header files, but do it @emph{after} all
directories specified with @option{-I} and the standard system directories
have been exhausted. @var{dir} is treated as a system include directory.
+If @var{dir} begins with @code{=}, then the @code{=} will be replaced
+by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
@item -iprefix @var{prefix}
@opindex iprefix
path. @option{-iwithprefixbefore} puts it in the same place @option{-I}
would; @option{-iwithprefix} puts it where @option{-idirafter} would.
-Use of these options is discouraged.
+@item -isysroot @var{dir}
+@opindex isysroot
+This option is like the @option{--sysroot} option, but applies only to
+header files. See the @option{--sysroot} option for more information.
+
+@item -imultilib @var{dir}
+@opindex imultilib
+Use @var{dir} as a subdirectory of the directory containing
+target-specific C++ headers.
@item -isystem @var{dir}
@opindex isystem
@ifset cppmanual
@xref{System Headers}.
@end ifset
+If @var{dir} begins with @code{=}, then the @code{=} will be replaced
+by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -iquote @var{dir}
+@opindex iquote
+Search @var{dir} only for header files requested with
+@code{@w{#include "@var{file}"}}; they are not searched for
+@code{@w{#include <@var{file}>}}, before all directories specified by
+@option{-I} and before the standard system directories.
+@ifset cppmanual
+@xref{Search Path}.
+@end ifset
+If @var{dir} begins with @code{=}, then the @code{=} will be replaced
+by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -fdirectives-only
+@opindex fdirectives-only
+When preprocessing, handle directives, but do not expand macros.
+
+The option's behavior depends on the @option{-E} and @option{-fpreprocessed}
+options.
+
+With @option{-E}, preprocessing is limited to the handling of directives
+such as @code{#define}, @code{#ifdef}, and @code{#error}. Other
+preprocessor operations, such as macro expansion and trigraph
+conversion are not performed. In addition, the @option{-dD} option is
+implicitly enabled.
+
+With @option{-fpreprocessed}, predefinition of command line and most
+builtin macros is disabled. Macros such as @code{__LINE__}, which are
+contextually dependent, are handled normally. This enables compilation of
+files previously preprocessed with @code{-E -fdirectives-only}.
+
+With both @option{-E} and @option{-fpreprocessed}, the rules for
+@option{-fpreprocessed} take precedence. This enables full preprocessing of
+files previously preprocessed with @code{-E -fdirectives-only}.
+
+@item -fdollars-in-identifiers
+@opindex fdollars-in-identifiers
+@anchor{fdollars-in-identifiers}
+Accept @samp{$} in identifiers.
+@ifset cppmanual
+@xref{Identifier characters}.
+@end ifset
+
+@item -fextended-identifiers
+@opindex fextended-identifiers
+Accept universal character names in identifiers. This option is
+experimental; in a future version of GCC, it will be enabled by
+default for C99 and C++.
@item -fpreprocessed
@opindex fpreprocessed
line. If the value is less than 1 or greater than 100, the option is
ignored. The default is 8.
+@item -fexec-charset=@var{charset}
+@opindex fexec-charset
+@cindex character set, execution
+Set the execution character set, used for string and character
+constants. The default is UTF-8. @var{charset} can be any encoding
+supported by the system's @code{iconv} library routine.
+
+@item -fwide-exec-charset=@var{charset}
+@opindex fwide-exec-charset
+@cindex character set, wide execution
+Set the wide execution character set, used for wide string and
+character constants. The default is UTF-32 or UTF-16, whichever
+corresponds to the width of @code{wchar_t}. As with
+@option{-fexec-charset}, @var{charset} can be any encoding supported
+by the system's @code{iconv} library routine; however, you will have
+problems with encodings that do not fit exactly in @code{wchar_t}.
+
+@item -finput-charset=@var{charset}
+@opindex finput-charset
+@cindex character set, input
+Set the input character set, used for translation from the character
+set of the input file to the source character set used by GCC@. If the
+locale does not specify, or GCC cannot get this information from the
+locale, the default is UTF-8. This can be overridden by either the locale
+or this command line option. Currently the command line option takes
+precedence if there's a conflict. @var{charset} can be any encoding
+supported by the system's @code{iconv} library routine.
+
+@item -fworking-directory
+@opindex fworking-directory
+@opindex fno-working-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. GCC will use this
+directory, when it's 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 @option{-fno-working-directory}. If the @option{-P} flag is
+present in the command line, this option has no effect, since no
+@code{#line} directives are emitted whatsoever.
+
@item -fno-show-column
@opindex fno-show-column
Do not print column numbers in diagnostics. This may be necessary if
@var{predicate}(@var{answer})}, which is still supported, because
it does not use shell special characters.
@ifset cppmanual
-@xref{Assertions}.
+@xref{Obsolete Features}.
@end ifset
@item -A -@var{predicate}=@var{answer}
Cancel an assertion with the predicate @var{predicate} and answer
@var{answer}.
-@item -A-
-@opindex A-
-Cancel all predefined assertions and all assertions preceding it on
-the command line. Also, undefine all predefined macros and all
-macros preceding it on the command line. (This is a historical wart and
-may change in the future.)
-
@item -dCHARS
@var{CHARS} is a sequence of one or more of the following characters,
and must not be preceded by a space. Other characters are interpreted
finding out what is predefined in your version of the preprocessor.
Assuming you have no file @file{foo.h}, the command
-@example
+@smallexample
touch foo.h; cpp -dM foo.h
-@end example
+@end smallexample
@noindent
will show all the predefined macros.
+If you use @option{-dM} without the @option{-E} option, @option{-dM} is
+interpreted as a synonym for @option{-fdump-rtl-mach}.
+@xref{Debugging Options, , ,gcc}.
+
@item D
@opindex dD
Like @samp{M} except in two respects: it does @emph{not} include the
@opindex dI
Output @samp{#include} directives in addition to the result of
preprocessing.
+
+@item U
+@opindex dU
+Like @samp{D} 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
+@samp{#undef} directives are also output for macros tested but
+undefined at the time.
@end table
@item -P
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 @samp{#}.
-@item -gcc
-@opindex gcc
-Define the macros @sc{__gnuc__}, @sc{__gnuc_minor__} and
-@sc{__gnuc_patchlevel__}. These are defined automatically when you use
-@command{gcc -E}; you can turn them off in that case with
-@option{-no-gcc}.
-
-@item -traditional
-@opindex traditional
-Try to imitate the behavior of old-fashioned C, as opposed to ISO
-C@.
+@item -CC
+Do not discard comments, including during macro expansion. This is
+like @option{-C}, except that comments contained within macros are
+also passed through to the output file where the macro is expanded.
+
+In addition to the side-effects of the @option{-C} option, the
+@option{-CC} 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 @option{-CC} option is generally used to support lint comments.
+
+@item -traditional-cpp
+@opindex traditional-cpp
+Try to imitate the behavior of old-fashioned C preprocessors, as
+opposed to ISO C preprocessors.
@ifset cppmanual
@xref{Traditional Mode}.
@end ifset
Enable special code to work around file systems which only permit very
short file names, such as MS-DOS@.
-@item -$
-@opindex $
-Forbid the use of @samp{$} in identifiers. The C standard allows
-implementations to define extra characters that can appear in
-identifiers. By default GNU CPP permits @samp{$}, a common extension.
-
-@item -h
@itemx --help
@itemx --target-help
-@opindex h
@opindex help
@opindex target-help
Print text describing all the command line options instead of
@opindex 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
-@samp{#include} stack it is.
+@samp{#include} stack it is. Precompiled header files are also
+printed, even if they are found to be invalid; an invalid precompiled
+header file is printed with @samp{...x} and a valid one with @samp{...!} .
@item -version
@itemx --version
projects / msp430-gcc.git / blobdiff