[doc, 2/n] invoke.texi: move spec file section

[Sandra Loosemore <sandra at codesourcery dot com>]

I've checked in this patch to move the section that documents spec file 
formats towards the end of the invoke.texi chapter, so it isn't stuck 
randomly in the middle of the discussion of unrelated command-line 
options.  I made no changes to the text of the section being moved here.

-Sandra

2016-01-12  Sandra Loosemore <sandra@codesourcery.com>

	gcc/
	* doc/invoke.texi (Spec Files): Move section down in file, past
	all command-line option descriptions.

Index: gcc/doc/invoke.texi
===================================================================
--- gcc/doc/invoke.texi	(revision 232306)
+++ gcc/doc/invoke.texi	(working copy)
@@ -146,11 +146,11 @@ only one of these two forms, whichever o
 * Link Options::        Specifying libraries and so on.
 * Directory Options::   Where to find header files and libraries.
                         Where to find the compiler executable files.
-* Spec Files::          How to pass switches to sub-processes.
 * Submodel Options::    Specifying minor hardware or convention variations,
                         such as 68010 vs 68020.
 * Code Gen Options::    Specifying conventions for function calls, data layout
                         and register usage.
+* Spec Files::          How to pass switches to sub-processes.
 * Environment Variables:: Env vars that affect GCC.
 * Precompiled Headers:: Compiling a header once, and using it many times.
 @end menu
@@ -11840,586 +11840,6 @@ for header files.  Thus, @option{-I-} an
 independent.
 @end table
 
-@c man end
-
-@node Spec Files
-@section Specifying Subprocesses and the Switches to Pass to Them
-@cindex Spec Files
-
-@command{gcc} is a driver program.  It performs its job by invoking a
-sequence of other programs to do the work of compiling, assembling and
-linking.  GCC interprets its command-line parameters and uses these to
-deduce which programs it should invoke, and which command-line options
-it ought to place on their command lines.  This behavior is controlled
-by @dfn{spec strings}.  In most cases there is one spec string for each
-program that GCC can invoke, but a few programs have multiple spec
-strings to control their behavior.  The spec strings built into GCC can
-be overridden by using the @option{-specs=} command-line switch to specify
-a spec file.
-
-@dfn{Spec files} are plaintext files that are used to construct spec
-strings.  They consist of a sequence of directives separated by blank
-lines.  The type of directive is determined by the first non-whitespace
-character on the line, which can be one of the following:
-
-@table @code
-@item %@var{command}
-Issues a @var{command} to the spec file processor.  The commands that can
-appear here are:
-
-@table @code
-@item %include <@var{file}>
-@cindex @code{%include}
-Search for @var{file} and insert its text at the current point in the
-specs file.
-
-@item %include_noerr <@var{file}>
-@cindex @code{%include_noerr}
-Just like @samp{%include}, but do not generate an error message if the include
-file cannot be found.
-
-@item %rename @var{old_name} @var{new_name}
-@cindex @code{%rename}
-Rename the spec string @var{old_name} to @var{new_name}.
-
-@end table
-
-@item *[@var{spec_name}]:
-This tells the compiler to create, override or delete the named spec
-string.  All lines after this directive up to the next directive or
-blank line are considered to be the text for the spec string.  If this
-results in an empty string then the spec is deleted.  (Or, if the
-spec did not exist, then nothing happens.)  Otherwise, if the spec
-does not currently exist a new spec is created.  If the spec does
-exist then its contents are overridden by the text of this
-directive, unless the first character of that text is the @samp{+}
-character, in which case the text is appended to the spec.
-
-@item [@var{suffix}]:
-Creates a new @samp{[@var{suffix}] spec} pair.  All lines after this directive
-and up to the next directive or blank line are considered to make up the
-spec string for the indicated suffix.  When the compiler encounters an
-input file with the named suffix, it processes the spec string in
-order to work out how to compile that file.  For example:
-
-@smallexample
-.ZZ:
-z-compile -input %i
-@end smallexample
-
-This says that any input file whose name ends in @samp{.ZZ} should be
-passed to the program @samp{z-compile}, which should be invoked with the
-command-line switch @option{-input} and with the result of performing the
-@samp{%i} substitution.  (See below.)
-
-As an alternative to providing a spec string, the text following a
-suffix directive can be one of the following:
-
-@table @code
-@item @@@var{language}
-This says that the suffix is an alias for a known @var{language}.  This is
-similar to using the @option{-x} command-line switch to GCC to specify a
-language explicitly.  For example:
-
-@smallexample
-.ZZ:
-@@c++
-@end smallexample
-
-Says that .ZZ files are, in fact, C++ source files.
-
-@item #@var{name}
-This causes an error messages saying:
-
-@smallexample
-@var{name} compiler not installed on this system.
-@end smallexample
-@end table
-
-GCC already has an extensive list of suffixes built into it.
-This directive adds an entry to the end of the list of suffixes, but
-since the list is searched from the end backwards, it is effectively
-possible to override earlier entries using this technique.
-
-@end table
-
-GCC has the following spec strings built into it.  Spec files can
-override these strings or create their own.  Note that individual
-targets can also add their own spec strings to this list.
-
-@smallexample
-asm          Options to pass to the assembler
-asm_final    Options to pass to the assembler post-processor
-cpp          Options to pass to the C preprocessor
-cc1          Options to pass to the C compiler
-cc1plus      Options to pass to the C++ compiler
-endfile      Object files to include at the end of the link
-link         Options to pass to the linker
-lib          Libraries to include on the command line to the linker
-libgcc       Decides which GCC support library to pass to the linker
-linker       Sets the name of the linker
-predefines   Defines to be passed to the C preprocessor
-signed_char  Defines to pass to CPP to say whether @code{char} is signed
-             by default
-startfile    Object files to include at the start of the link
-@end smallexample
-
-Here is a small example of a spec file:
-
-@smallexample
-%rename lib                 old_lib
-
-*lib:
---start-group -lgcc -lc -leval1 --end-group %(old_lib)
-@end smallexample
-
-This example renames the spec called @samp{lib} to @samp{old_lib} and
-then overrides the previous definition of @samp{lib} with a new one.
-The new definition adds in some extra command-line options before
-including the text of the old definition.
-
-@dfn{Spec strings} are a list of command-line options to be passed to their
-corresponding program.  In addition, the spec strings can contain
-@samp{%}-prefixed sequences to substitute variable text or to
-conditionally insert text into the command line.  Using these constructs
-it is possible to generate quite complex command lines.
-
-Here is a table of all defined @samp{%}-sequences for spec
-strings.  Note that spaces are not generated automatically around the
-results of expanding these sequences.  Therefore you can concatenate them
-together or combine them with constant text in a single argument.
-
-@table @code
-@item %%
-Substitute one @samp{%} into the program name or argument.
-
-@item %i
-Substitute the name of the input file being processed.
-
-@item %b
-Substitute the basename of the input file being processed.
-This is the substring up to (and not including) the last period
-and not including the directory.
-
-@item %B
-This is the same as @samp{%b}, but include the file suffix (text after
-the last period).
-
-@item %d
-Marks the argument containing or following the @samp{%d} as a
-temporary file name, so that that file is deleted if GCC exits
-successfully.  Unlike @samp{%g}, this contributes no text to the
-argument.
-
-@item %g@var{suffix}
-Substitute a file name that has suffix @var{suffix} and is chosen
-once per compilation, and mark the argument in the same way as
-@samp{%d}.  To reduce exposure to denial-of-service attacks, the file
-name is now chosen in a way that is hard to predict even when previously
-chosen file names are known.  For example, @samp{%g.s @dots{} %g.o @dots{} %g.s}
-might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}.  @var{suffix} matches
-the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is
-treated exactly as if @samp{%O} had been preprocessed.  Previously, @samp{%g}
-was simply substituted with a file name chosen once per compilation,
-without regard to any appended suffix (which was therefore treated
-just like ordinary text), making such attacks more likely to succeed.
-
-@item %u@var{suffix}
-Like @samp{%g}, but generates a new temporary file name
-each time it appears instead of once per compilation.
-
-@item %U@var{suffix}
-Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a
-new one if there is no such last file name.  In the absence of any
-@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share
-the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s}
-involves the generation of two distinct file names, one
-for each @samp{%g.s} and another for each @samp{%U.s}.  Previously, @samp{%U} was
-simply substituted with a file name chosen for the previous @samp{%u},
-without regard to any appended suffix.
-
-@item %j@var{suffix}
-Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is
-writable, and if @option{-save-temps} is not used; 
-otherwise, substitute the name
-of a temporary file, just like @samp{%u}.  This temporary file is not
-meant for communication between processes, but rather as a junk
-disposal mechanism.
-
-@item %|@var{suffix}
-@itemx %m@var{suffix}
-Like @samp{%g}, except if @option{-pipe} is in effect.  In that case
-@samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at
-all.  These are the two most common ways to instruct a program that it
-should read from standard input or write to standard output.  If you
-need something more elaborate you can use an @samp{%@{pipe:@code{X}@}}
-construct: see for example @file{f/lang-specs.h}.
-
-@item %.@var{SUFFIX}
-Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args
-when it is subsequently output with @samp{%*}.  @var{SUFFIX} is
-terminated by the next space or %.
-
-@item %w
-Marks the argument containing or following the @samp{%w} as the
-designated output file of this compilation.  This puts the argument
-into the sequence of arguments that @samp{%o} substitutes.
-
-@item %o
-Substitutes the names of all the output files, with spaces
-automatically placed around them.  You should write spaces
-around the @samp{%o} as well or the results are undefined.
-@samp{%o} is for use in the specs for running the linker.
-Input files whose names have no recognized suffix are not compiled
-at all, but they are included among the output files, so they are
-linked.
-
-@item %O
-Substitutes the suffix for object files.  Note that this is
-handled specially when it immediately follows @samp{%g, %u, or %U},
-because of the need for those to form complete file names.  The
-handling is such that @samp{%O} is treated exactly as if it had already
-been substituted, except that @samp{%g, %u, and %U} do not currently
-support additional @var{suffix} characters following @samp{%O} as they do
-following, for example, @samp{.o}.
-
-@item %p
-Substitutes the standard macro predefinitions for the
-current target machine.  Use this when running @command{cpp}.
-
-@item %P
-Like @samp{%p}, but puts @samp{__} before and after the name of each
-predefined macro, except for macros that start with @samp{__} or with
-@samp{_@var{L}}, where @var{L} is an uppercase letter.  This is for ISO
-C@.
-
-@item %I
-Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}),
-@option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}),
-@option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options)
-and @option{-imultilib} as necessary.
-
-@item %s
-Current argument is the name of a library or startup file of some sort.
-Search for that file in a standard list of directories and substitute
-the full name found.  The current working directory is included in the
-list of directories scanned.
-
-@item %T
-Current argument is the name of a linker script.  Search for that file
-in the current list of directories to scan for libraries. If the file
-is located insert a @option{--script} option into the command line
-followed by the full path name found.  If the file is not found then
-generate an error message.  Note: the current working directory is not
-searched.
-
-@item %e@var{str}
-Print @var{str} as an error message.  @var{str} is terminated by a newline.
-Use this when inconsistent options are detected.
-
-@item %(@var{name})
-Substitute the contents of spec string @var{name} at this point.
-
-@item %x@{@var{option}@}
-Accumulate an option for @samp{%X}.
-
-@item %X
-Output the accumulated linker options specified by @option{-Wl} or a @samp{%x}
-spec string.
-
-@item %Y
-Output the accumulated assembler options specified by @option{-Wa}.
-
-@item %Z
-Output the accumulated preprocessor options specified by @option{-Wp}.
-
-@item %a
-Process the @code{asm} spec.  This is used to compute the
-switches to be passed to the assembler.
-
-@item %A
-Process the @code{asm_final} spec.  This is a spec string for
-passing switches to an assembler post-processor, if such a program is
-needed.
-
-@item %l
-Process the @code{link} spec.  This is the spec for computing the
-command line passed to the linker.  Typically it makes use of the
-@samp{%L %G %S %D and %E} sequences.
-
-@item %D
-Dump out a @option{-L} option for each directory that GCC believes might
-contain startup files.  If the target supports multilibs then the
-current multilib directory is prepended to each of these paths.
-
-@item %L
-Process the @code{lib} spec.  This is a spec string for deciding which
-libraries are included on the command line to the linker.
-
-@item %G
-Process the @code{libgcc} spec.  This is a spec string for deciding
-which GCC support library is included on the command line to the linker.
-
-@item %S
-Process the @code{startfile} spec.  This is a spec for deciding which
-object files are the first ones passed to the linker.  Typically
-this might be a file named @file{crt0.o}.
-
-@item %E
-Process the @code{endfile} spec.  This is a spec string that specifies
-the last object files that are passed to the linker.
-
-@item %C
-Process the @code{cpp} spec.  This is used to construct the arguments
-to be passed to the C preprocessor.
-
-@item %1
-Process the @code{cc1} spec.  This is used to construct the options to be
-passed to the actual C compiler (@command{cc1}).
-
-@item %2
-Process the @code{cc1plus} spec.  This is used to construct the options to be
-passed to the actual C++ compiler (@command{cc1plus}).
-
-@item %*
-Substitute the variable part of a matched option.  See below.
-Note that each comma in the substituted string is replaced by
-a single space.
-
-@item %<@code{S}
-Remove all occurrences of @code{-S} from the command line.  Note---this
-command is position dependent.  @samp{%} commands in the spec string
-before this one see @code{-S}, @samp{%} commands in the spec string
-after this one do not.
-
-@item %:@var{function}(@var{args})
-Call the named function @var{function}, passing it @var{args}.
-@var{args} is first processed as a nested spec string, then split
-into an argument vector in the usual fashion.  The function returns
-a string which is processed as if it had appeared literally as part
-of the current spec.
-
-The following built-in spec functions are provided:
-
-@table @code
-@item @code{getenv}
-The @code{getenv} spec function takes two arguments: an environment
-variable name and a string.  If the environment variable is not
-defined, a fatal error is issued.  Otherwise, the return value is the
-value of the environment variable concatenated with the string.  For
-example, if @env{TOPDIR} is defined as @file{/path/to/top}, then:
-
-@smallexample
-%:getenv(TOPDIR /include)
-@end smallexample
-
-expands to @file{/path/to/top/include}.
-
-@item @code{if-exists}
-The @code{if-exists} spec function takes one argument, an absolute
-pathname to a file.  If the file exists, @code{if-exists} returns the
-pathname.  Here is a small example of its usage:
-
-@smallexample
-*startfile:
-crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s
-@end smallexample
-
-@item @code{if-exists-else}
-The @code{if-exists-else} spec function is similar to the @code{if-exists}
-spec function, except that it takes two arguments.  The first argument is
-an absolute pathname to a file.  If the file exists, @code{if-exists-else}
-returns the pathname.  If it does not exist, it returns the second argument.
-This way, @code{if-exists-else} can be used to select one file or another,
-based on the existence of the first.  Here is a small example of its usage:
-
-@smallexample
-*startfile:
-crt0%O%s %:if-exists(crti%O%s) \
-%:if-exists-else(crtbeginT%O%s crtbegin%O%s)
-@end smallexample
-
-@item @code{replace-outfile}
-The @code{replace-outfile} spec function takes two arguments.  It looks for the
-first argument in the outfiles array and replaces it with the second argument.  Here
-is a small example of its usage:
-
-@smallexample
-%@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@}
-@end smallexample
-
-@item @code{remove-outfile}
-The @code{remove-outfile} spec function takes one argument.  It looks for the
-first argument in the outfiles array and removes it.  Here is a small example
-its usage:
-
-@smallexample
-%:remove-outfile(-lm)
-@end smallexample
-
-@item @code{pass-through-libs}
-The @code{pass-through-libs} spec function takes any number of arguments.  It
-finds any @option{-l} options and any non-options ending in @file{.a} (which it
-assumes are the names of linker input library archive files) and returns a
-result containing all the found arguments each prepended by
-@option{-plugin-opt=-pass-through=} and joined by spaces.  This list is
-intended to be passed to the LTO linker plugin.
-
-@smallexample
-%:pass-through-libs(%G %L %G)
-@end smallexample
-
-@item @code{print-asm-header}
-The @code{print-asm-header} function takes no arguments and simply
-prints a banner like:
-
-@smallexample
-Assembler options
-=================
-
-Use "-Wa,OPTION" to pass "OPTION" to the assembler.
-@end smallexample
-
-It is used to separate compiler options from assembler options
-in the @option{--target-help} output.
-@end table
-
-@item %@{@code{S}@}
-Substitutes the @code{-S} switch, if that switch is given to GCC@.
-If that switch is not specified, this substitutes nothing.  Note that
-the leading dash is omitted when specifying this option, and it is
-automatically inserted if the substitution is performed.  Thus the spec
-string @samp{%@{foo@}} matches the command-line option @option{-foo}
-and outputs the command-line option @option{-foo}.
-
-@item %W@{@code{S}@}
-Like %@{@code{S}@} but mark last argument supplied within as a file to be
-deleted on failure.
-
-@item %@{@code{S}*@}
-Substitutes all the switches specified to GCC whose names start
-with @code{-S}, but which also take an argument.  This is used for
-switches like @option{-o}, @option{-D}, @option{-I}, etc.
-GCC considers @option{-o foo} as being
-one switch whose name starts with @samp{o}.  %@{o*@} substitutes this
-text, including the space.  Thus two arguments are generated.
-
-@item %@{@code{S}*&@code{T}*@}
-Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options
-(the order of @code{S} and @code{T} in the spec is not significant).
-There can be any number of ampersand-separated variables; for each the
-wild card is optional.  Useful for CPP as @samp{%@{D*&U*&A*@}}.
-
-@item %@{@code{S}:@code{X}@}
-Substitutes @code{X}, if the @option{-S} switch is given to GCC@.
-
-@item %@{!@code{S}:@code{X}@}
-Substitutes @code{X}, if the @option{-S} switch is @emph{not} given to GCC@.
-
-@item %@{@code{S}*:@code{X}@}
-Substitutes @code{X} if one or more switches whose names start with
-@code{-S} are specified to GCC@.  Normally @code{X} is substituted only
-once, no matter how many such switches appeared.  However, if @code{%*}
-appears somewhere in @code{X}, then @code{X} is substituted once
-for each matching switch, with the @code{%*} replaced by the part of
-that switch matching the @code{*}.
-
-If @code{%*} appears as the last part of a spec sequence then a space
-is added after the end of the last substitution.  If there is more
-text in the sequence, however, then a space is not generated.  This
-allows the @code{%*} substitution to be used as part of a larger
-string.  For example, a spec string like this:
-
-@smallexample
-%@{mcu=*:--script=%*/memory.ld@}
-@end smallexample
-
-@noindent
-when matching an option like @option{-mcu=newchip} produces:
-
-@smallexample
---script=newchip/memory.ld
-@end smallexample
-
-@item %@{.@code{S}:@code{X}@}
-Substitutes @code{X}, if processing a file with suffix @code{S}.
-
-@item %@{!.@code{S}:@code{X}@}
-Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}.
-
-@item %@{,@code{S}:@code{X}@}
-Substitutes @code{X}, if processing a file for language @code{S}.
-
-@item %@{!,@code{S}:@code{X}@}
-Substitutes @code{X}, if not processing a file for language @code{S}.
-
-@item %@{@code{S}|@code{P}:@code{X}@}
-Substitutes @code{X} if either @code{-S} or @code{-P} is given to
-GCC@.  This may be combined with @samp{!}, @samp{.}, @samp{,}, and
-@code{*} sequences as well, although they have a stronger binding than
-the @samp{|}.  If @code{%*} appears in @code{X}, all of the
-alternatives must be starred, and only the first matching alternative
-is substituted.
-
-For example, a spec string like this:
-
-@smallexample
-%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@}
-@end smallexample
-
-@noindent
-outputs the following command-line options from the following input
-command-line options:
-
-@smallexample
-fred.c        -foo -baz
-jim.d         -bar -boggle
--d fred.c     -foo -baz -boggle
--d jim.d      -bar -baz -boggle
-@end smallexample
-
-@item %@{S:X; T:Y; :D@}
-
-If @code{S} is given to GCC, substitutes @code{X}; else if @code{T} is
-given to GCC, substitutes @code{Y}; else substitutes @code{D}.  There can
-be as many clauses as you need.  This may be combined with @code{.},
-@code{,}, @code{!}, @code{|}, and @code{*} as needed.
-
-
-@end table
-
-The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar
-construct may contain other nested @samp{%} constructs or spaces, or
-even newlines.  They are processed as usual, as described above.
-Trailing white space in @code{X} is ignored.  White space may also
-appear anywhere on the left side of the colon in these constructs,
-except between @code{.} or @code{*} and the corresponding word.
-
-The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are
-handled specifically in these constructs.  If another value of
-@option{-O} or the negated form of a @option{-f}, @option{-m}, or
-@option{-W} switch is found later in the command line, the earlier
-switch value is ignored, except with @{@code{S}*@} where @code{S} is
-just one letter, which passes all matching options.
-
-The character @samp{|} at the beginning of the predicate text is used to
-indicate that a command should be piped to the following command, but
-only if @option{-pipe} is specified.
-
-It is built into GCC which switches take arguments and which do not.
-(You might think it would be useful to generalize this to allow each
-compiler's spec to say which switches take arguments.  But this cannot
-be done in a consistent fashion.  GCC cannot even decide which input
-files have been specified without knowing which switches take arguments,
-and it must know which input files to compile in order to tell which
-compilers to run).
-
-GCC also knows implicitly that arguments starting in @option{-l} are to be
-treated as compiler output files, and passed to the linker in their
-proper position among the other output files.
-
-@c man begin OPTIONS
-
 @node Submodel Options
 @section Hardware Models and Configurations
 @cindex submodel options
@@ -24816,6 +24236,582 @@ the implementation of the @file{libatomi
 
 @c man end
 
+@node Spec Files
+@section Specifying Subprocesses and the Switches to Pass to Them
+@cindex Spec Files
+
+@command{gcc} is a driver program.  It performs its job by invoking a
+sequence of other programs to do the work of compiling, assembling and
+linking.  GCC interprets its command-line parameters and uses these to
+deduce which programs it should invoke, and which command-line options
+it ought to place on their command lines.  This behavior is controlled
+by @dfn{spec strings}.  In most cases there is one spec string for each
+program that GCC can invoke, but a few programs have multiple spec
+strings to control their behavior.  The spec strings built into GCC can
+be overridden by using the @option{-specs=} command-line switch to specify
+a spec file.
+
+@dfn{Spec files} are plaintext files that are used to construct spec
+strings.  They consist of a sequence of directives separated by blank
+lines.  The type of directive is determined by the first non-whitespace
+character on the line, which can be one of the following:
+
+@table @code
+@item %@var{command}
+Issues a @var{command} to the spec file processor.  The commands that can
+appear here are:
+
+@table @code
+@item %include <@var{file}>
+@cindex @code{%include}
+Search for @var{file} and insert its text at the current point in the
+specs file.
+
+@item %include_noerr <@var{file}>
+@cindex @code{%include_noerr}
+Just like @samp{%include}, but do not generate an error message if the include
+file cannot be found.
+
+@item %rename @var{old_name} @var{new_name}
+@cindex @code{%rename}
+Rename the spec string @var{old_name} to @var{new_name}.
+
+@end table
+
+@item *[@var{spec_name}]:
+This tells the compiler to create, override or delete the named spec
+string.  All lines after this directive up to the next directive or
+blank line are considered to be the text for the spec string.  If this
+results in an empty string then the spec is deleted.  (Or, if the
+spec did not exist, then nothing happens.)  Otherwise, if the spec
+does not currently exist a new spec is created.  If the spec does
+exist then its contents are overridden by the text of this
+directive, unless the first character of that text is the @samp{+}
+character, in which case the text is appended to the spec.
+
+@item [@var{suffix}]:
+Creates a new @samp{[@var{suffix}] spec} pair.  All lines after this directive
+and up to the next directive or blank line are considered to make up the
+spec string for the indicated suffix.  When the compiler encounters an
+input file with the named suffix, it processes the spec string in
+order to work out how to compile that file.  For example:
+
+@smallexample
+.ZZ:
+z-compile -input %i
+@end smallexample
+
+This says that any input file whose name ends in @samp{.ZZ} should be
+passed to the program @samp{z-compile}, which should be invoked with the
+command-line switch @option{-input} and with the result of performing the
+@samp{%i} substitution.  (See below.)
+
+As an alternative to providing a spec string, the text following a
+suffix directive can be one of the following:
+
+@table @code
+@item @@@var{language}
+This says that the suffix is an alias for a known @var{language}.  This is
+similar to using the @option{-x} command-line switch to GCC to specify a
+language explicitly.  For example:
+
+@smallexample
+.ZZ:
+@@c++
+@end smallexample
+
+Says that .ZZ files are, in fact, C++ source files.
+
+@item #@var{name}
+This causes an error messages saying:
+
+@smallexample
+@var{name} compiler not installed on this system.
+@end smallexample
+@end table
+
+GCC already has an extensive list of suffixes built into it.
+This directive adds an entry to the end of the list of suffixes, but
+since the list is searched from the end backwards, it is effectively
+possible to override earlier entries using this technique.
+
+@end table
+
+GCC has the following spec strings built into it.  Spec files can
+override these strings or create their own.  Note that individual
+targets can also add their own spec strings to this list.
+
+@smallexample
+asm          Options to pass to the assembler
+asm_final    Options to pass to the assembler post-processor
+cpp          Options to pass to the C preprocessor
+cc1          Options to pass to the C compiler
+cc1plus      Options to pass to the C++ compiler
+endfile      Object files to include at the end of the link
+link         Options to pass to the linker
+lib          Libraries to include on the command line to the linker
+libgcc       Decides which GCC support library to pass to the linker
+linker       Sets the name of the linker
+predefines   Defines to be passed to the C preprocessor
+signed_char  Defines to pass to CPP to say whether @code{char} is signed
+             by default
+startfile    Object files to include at the start of the link
+@end smallexample
+
+Here is a small example of a spec file:
+
+@smallexample
+%rename lib                 old_lib
+
+*lib:
+--start-group -lgcc -lc -leval1 --end-group %(old_lib)
+@end smallexample
+
+This example renames the spec called @samp{lib} to @samp{old_lib} and
+then overrides the previous definition of @samp{lib} with a new one.
+The new definition adds in some extra command-line options before
+including the text of the old definition.
+
+@dfn{Spec strings} are a list of command-line options to be passed to their
+corresponding program.  In addition, the spec strings can contain
+@samp{%}-prefixed sequences to substitute variable text or to
+conditionally insert text into the command line.  Using these constructs
+it is possible to generate quite complex command lines.
+
+Here is a table of all defined @samp{%}-sequences for spec
+strings.  Note that spaces are not generated automatically around the
+results of expanding these sequences.  Therefore you can concatenate them
+together or combine them with constant text in a single argument.
+
+@table @code
+@item %%
+Substitute one @samp{%} into the program name or argument.
+
+@item %i
+Substitute the name of the input file being processed.
+
+@item %b
+Substitute the basename of the input file being processed.
+This is the substring up to (and not including) the last period
+and not including the directory.
+
+@item %B
+This is the same as @samp{%b}, but include the file suffix (text after
+the last period).
+
+@item %d
+Marks the argument containing or following the @samp{%d} as a
+temporary file name, so that that file is deleted if GCC exits
+successfully.  Unlike @samp{%g}, this contributes no text to the
+argument.
+
+@item %g@var{suffix}
+Substitute a file name that has suffix @var{suffix} and is chosen
+once per compilation, and mark the argument in the same way as
+@samp{%d}.  To reduce exposure to denial-of-service attacks, the file
+name is now chosen in a way that is hard to predict even when previously
+chosen file names are known.  For example, @samp{%g.s @dots{} %g.o @dots{} %g.s}
+might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}.  @var{suffix} matches
+the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is
+treated exactly as if @samp{%O} had been preprocessed.  Previously, @samp{%g}
+was simply substituted with a file name chosen once per compilation,
+without regard to any appended suffix (which was therefore treated
+just like ordinary text), making such attacks more likely to succeed.
+
+@item %u@var{suffix}
+Like @samp{%g}, but generates a new temporary file name
+each time it appears instead of once per compilation.
+
+@item %U@var{suffix}
+Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a
+new one if there is no such last file name.  In the absence of any
+@samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share
+the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s}
+involves the generation of two distinct file names, one
+for each @samp{%g.s} and another for each @samp{%U.s}.  Previously, @samp{%U} was
+simply substituted with a file name chosen for the previous @samp{%u},
+without regard to any appended suffix.
+
+@item %j@var{suffix}
+Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is
+writable, and if @option{-save-temps} is not used; 
+otherwise, substitute the name
+of a temporary file, just like @samp{%u}.  This temporary file is not
+meant for communication between processes, but rather as a junk
+disposal mechanism.
+
+@item %|@var{suffix}
+@itemx %m@var{suffix}
+Like @samp{%g}, except if @option{-pipe} is in effect.  In that case
+@samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at
+all.  These are the two most common ways to instruct a program that it
+should read from standard input or write to standard output.  If you
+need something more elaborate you can use an @samp{%@{pipe:@code{X}@}}
+construct: see for example @file{f/lang-specs.h}.
+
+@item %.@var{SUFFIX}
+Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args
+when it is subsequently output with @samp{%*}.  @var{SUFFIX} is
+terminated by the next space or %.
+
+@item %w
+Marks the argument containing or following the @samp{%w} as the
+designated output file of this compilation.  This puts the argument
+into the sequence of arguments that @samp{%o} substitutes.
+
+@item %o
+Substitutes the names of all the output files, with spaces
+automatically placed around them.  You should write spaces
+around the @samp{%o} as well or the results are undefined.
+@samp{%o} is for use in the specs for running the linker.
+Input files whose names have no recognized suffix are not compiled
+at all, but they are included among the output files, so they are
+linked.
+
+@item %O
+Substitutes the suffix for object files.  Note that this is
+handled specially when it immediately follows @samp{%g, %u, or %U},
+because of the need for those to form complete file names.  The
+handling is such that @samp{%O} is treated exactly as if it had already
+been substituted, except that @samp{%g, %u, and %U} do not currently
+support additional @var{suffix} characters following @samp{%O} as they do
+following, for example, @samp{.o}.
+
+@item %p
+Substitutes the standard macro predefinitions for the
+current target machine.  Use this when running @command{cpp}.
+
+@item %P
+Like @samp{%p}, but puts @samp{__} before and after the name of each
+predefined macro, except for macros that start with @samp{__} or with
+@samp{_@var{L}}, where @var{L} is an uppercase letter.  This is for ISO
+C@.
+
+@item %I
+Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}),
+@option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}),
+@option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options)
+and @option{-imultilib} as necessary.
+
+@item %s
+Current argument is the name of a library or startup file of some sort.
+Search for that file in a standard list of directories and substitute
+the full name found.  The current working directory is included in the
+list of directories scanned.
+
+@item %T
+Current argument is the name of a linker script.  Search for that file
+in the current list of directories to scan for libraries. If the file
+is located insert a @option{--script} option into the command line
+followed by the full path name found.  If the file is not found then
+generate an error message.  Note: the current working directory is not
+searched.
+
+@item %e@var{str}
+Print @var{str} as an error message.  @var{str} is terminated by a newline.
+Use this when inconsistent options are detected.
+
+@item %(@var{name})
+Substitute the contents of spec string @var{name} at this point.
+
+@item %x@{@var{option}@}
+Accumulate an option for @samp{%X}.
+
+@item %X
+Output the accumulated linker options specified by @option{-Wl} or a @samp{%x}
+spec string.
+
+@item %Y
+Output the accumulated assembler options specified by @option{-Wa}.
+
+@item %Z
+Output the accumulated preprocessor options specified by @option{-Wp}.
+
+@item %a
+Process the @code{asm} spec.  This is used to compute the
+switches to be passed to the assembler.
+
+@item %A
+Process the @code{asm_final} spec.  This is a spec string for
+passing switches to an assembler post-processor, if such a program is
+needed.
+
+@item %l
+Process the @code{link} spec.  This is the spec for computing the
+command line passed to the linker.  Typically it makes use of the
+@samp{%L %G %S %D and %E} sequences.
+
+@item %D
+Dump out a @option{-L} option for each directory that GCC believes might
+contain startup files.  If the target supports multilibs then the
+current multilib directory is prepended to each of these paths.
+
+@item %L
+Process the @code{lib} spec.  This is a spec string for deciding which
+libraries are included on the command line to the linker.
+
+@item %G
+Process the @code{libgcc} spec.  This is a spec string for deciding
+which GCC support library is included on the command line to the linker.
+
+@item %S
+Process the @code{startfile} spec.  This is a spec for deciding which
+object files are the first ones passed to the linker.  Typically
+this might be a file named @file{crt0.o}.
+
+@item %E
+Process the @code{endfile} spec.  This is a spec string that specifies
+the last object files that are passed to the linker.
+
+@item %C
+Process the @code{cpp} spec.  This is used to construct the arguments
+to be passed to the C preprocessor.
+
+@item %1
+Process the @code{cc1} spec.  This is used to construct the options to be
+passed to the actual C compiler (@command{cc1}).
+
+@item %2
+Process the @code{cc1plus} spec.  This is used to construct the options to be
+passed to the actual C++ compiler (@command{cc1plus}).
+
+@item %*
+Substitute the variable part of a matched option.  See below.
+Note that each comma in the substituted string is replaced by
+a single space.
+
+@item %<@code{S}
+Remove all occurrences of @code{-S} from the command line.  Note---this
+command is position dependent.  @samp{%} commands in the spec string
+before this one see @code{-S}, @samp{%} commands in the spec string
+after this one do not.
+
+@item %:@var{function}(@var{args})
+Call the named function @var{function}, passing it @var{args}.
+@var{args} is first processed as a nested spec string, then split
+into an argument vector in the usual fashion.  The function returns
+a string which is processed as if it had appeared literally as part
+of the current spec.
+
+The following built-in spec functions are provided:
+
+@table @code
+@item @code{getenv}
+The @code{getenv} spec function takes two arguments: an environment
+variable name and a string.  If the environment variable is not
+defined, a fatal error is issued.  Otherwise, the return value is the
+value of the environment variable concatenated with the string.  For
+example, if @env{TOPDIR} is defined as @file{/path/to/top}, then:
+
+@smallexample
+%:getenv(TOPDIR /include)
+@end smallexample
+
+expands to @file{/path/to/top/include}.
+
+@item @code{if-exists}
+The @code{if-exists} spec function takes one argument, an absolute
+pathname to a file.  If the file exists, @code{if-exists} returns the
+pathname.  Here is a small example of its usage:
+
+@smallexample
+*startfile:
+crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s
+@end smallexample
+
+@item @code{if-exists-else}
+The @code{if-exists-else} spec function is similar to the @code{if-exists}
+spec function, except that it takes two arguments.  The first argument is
+an absolute pathname to a file.  If the file exists, @code{if-exists-else}
+returns the pathname.  If it does not exist, it returns the second argument.
+This way, @code{if-exists-else} can be used to select one file or another,
+based on the existence of the first.  Here is a small example of its usage:
+
+@smallexample
+*startfile:
+crt0%O%s %:if-exists(crti%O%s) \
+%:if-exists-else(crtbeginT%O%s crtbegin%O%s)
+@end smallexample
+
+@item @code{replace-outfile}
+The @code{replace-outfile} spec function takes two arguments.  It looks for the
+first argument in the outfiles array and replaces it with the second argument.  Here
+is a small example of its usage:
+
+@smallexample
+%@{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)@}
+@end smallexample
+
+@item @code{remove-outfile}
+The @code{remove-outfile} spec function takes one argument.  It looks for the
+first argument in the outfiles array and removes it.  Here is a small example
+its usage:
+
+@smallexample
+%:remove-outfile(-lm)
+@end smallexample
+
+@item @code{pass-through-libs}
+The @code{pass-through-libs} spec function takes any number of arguments.  It
+finds any @option{-l} options and any non-options ending in @file{.a} (which it
+assumes are the names of linker input library archive files) and returns a
+result containing all the found arguments each prepended by
+@option{-plugin-opt=-pass-through=} and joined by spaces.  This list is
+intended to be passed to the LTO linker plugin.
+
+@smallexample
+%:pass-through-libs(%G %L %G)
+@end smallexample
+
+@item @code{print-asm-header}
+The @code{print-asm-header} function takes no arguments and simply
+prints a banner like:
+
+@smallexample
+Assembler options
+=================
+
+Use "-Wa,OPTION" to pass "OPTION" to the assembler.
+@end smallexample
+
+It is used to separate compiler options from assembler options
+in the @option{--target-help} output.
+@end table
+
+@item %@{@code{S}@}
+Substitutes the @code{-S} switch, if that switch is given to GCC@.
+If that switch is not specified, this substitutes nothing.  Note that
+the leading dash is omitted when specifying this option, and it is
+automatically inserted if the substitution is performed.  Thus the spec
+string @samp{%@{foo@}} matches the command-line option @option{-foo}
+and outputs the command-line option @option{-foo}.
+
+@item %W@{@code{S}@}
+Like %@{@code{S}@} but mark last argument supplied within as a file to be
+deleted on failure.
+
+@item %@{@code{S}*@}
+Substitutes all the switches specified to GCC whose names start
+with @code{-S}, but which also take an argument.  This is used for
+switches like @option{-o}, @option{-D}, @option{-I}, etc.
+GCC considers @option{-o foo} as being
+one switch whose name starts with @samp{o}.  %@{o*@} substitutes this
+text, including the space.  Thus two arguments are generated.
+
+@item %@{@code{S}*&@code{T}*@}
+Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options
+(the order of @code{S} and @code{T} in the spec is not significant).
+There can be any number of ampersand-separated variables; for each the
+wild card is optional.  Useful for CPP as @samp{%@{D*&U*&A*@}}.
+
+@item %@{@code{S}:@code{X}@}
+Substitutes @code{X}, if the @option{-S} switch is given to GCC@.
+
+@item %@{!@code{S}:@code{X}@}
+Substitutes @code{X}, if the @option{-S} switch is @emph{not} given to GCC@.
+
+@item %@{@code{S}*:@code{X}@}
+Substitutes @code{X} if one or more switches whose names start with
+@code{-S} are specified to GCC@.  Normally @code{X} is substituted only
+once, no matter how many such switches appeared.  However, if @code{%*}
+appears somewhere in @code{X}, then @code{X} is substituted once
+for each matching switch, with the @code{%*} replaced by the part of
+that switch matching the @code{*}.
+
+If @code{%*} appears as the last part of a spec sequence then a space
+is added after the end of the last substitution.  If there is more
+text in the sequence, however, then a space is not generated.  This
+allows the @code{%*} substitution to be used as part of a larger
+string.  For example, a spec string like this:
+
+@smallexample
+%@{mcu=*:--script=%*/memory.ld@}
+@end smallexample
+
+@noindent
+when matching an option like @option{-mcu=newchip} produces:
+
+@smallexample
+--script=newchip/memory.ld
+@end smallexample
+
+@item %@{.@code{S}:@code{X}@}
+Substitutes @code{X}, if processing a file with suffix @code{S}.
+
+@item %@{!.@code{S}:@code{X}@}
+Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}.
+
+@item %@{,@code{S}:@code{X}@}
+Substitutes @code{X}, if processing a file for language @code{S}.
+
+@item %@{!,@code{S}:@code{X}@}
+Substitutes @code{X}, if not processing a file for language @code{S}.
+
+@item %@{@code{S}|@code{P}:@code{X}@}
+Substitutes @code{X} if either @code{-S} or @code{-P} is given to
+GCC@.  This may be combined with @samp{!}, @samp{.}, @samp{,}, and
+@code{*} sequences as well, although they have a stronger binding than
+the @samp{|}.  If @code{%*} appears in @code{X}, all of the
+alternatives must be starred, and only the first matching alternative
+is substituted.
+
+For example, a spec string like this:
+
+@smallexample
+%@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@}
+@end smallexample
+
+@noindent
+outputs the following command-line options from the following input
+command-line options:
+
+@smallexample
+fred.c        -foo -baz
+jim.d         -bar -boggle
+-d fred.c     -foo -baz -boggle
+-d jim.d      -bar -baz -boggle
+@end smallexample
+
+@item %@{S:X; T:Y; :D@}
+
+If @code{S} is given to GCC, substitutes @code{X}; else if @code{T} is
+given to GCC, substitutes @code{Y}; else substitutes @code{D}.  There can
+be as many clauses as you need.  This may be combined with @code{.},
+@code{,}, @code{!}, @code{|}, and @code{*} as needed.
+
+
+@end table
+
+The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar
+construct may contain other nested @samp{%} constructs or spaces, or
+even newlines.  They are processed as usual, as described above.
+Trailing white space in @code{X} is ignored.  White space may also
+appear anywhere on the left side of the colon in these constructs,
+except between @code{.} or @code{*} and the corresponding word.
+
+The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are
+handled specifically in these constructs.  If another value of
+@option{-O} or the negated form of a @option{-f}, @option{-m}, or
+@option{-W} switch is found later in the command line, the earlier
+switch value is ignored, except with @{@code{S}*@} where @code{S} is
+just one letter, which passes all matching options.
+
+The character @samp{|} at the beginning of the predicate text is used to
+indicate that a command should be piped to the following command, but
+only if @option{-pipe} is specified.
+
+It is built into GCC which switches take arguments and which do not.
+(You might think it would be useful to generalize this to allow each
+compiler's spec to say which switches take arguments.  But this cannot
+be done in a consistent fashion.  GCC cannot even decide which input
+files have been specified without knowing which switches take arguments,
+and it must know which input files to compile in order to tell which
+compilers to run).
+
+GCC also knows implicitly that arguments starting in @option{-l} are to be
+treated as compiler output files, and passed to the linker in their
+proper position among the other output files.
+
 @node Environment Variables
 @section Environment Variables Affecting GCC
 @cindex environment variables