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| <title>Using the GNU Compiler Collection (GCC): Spec Files</title> |
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| <a name="Spec-Files"></a> |
| <div class="header"> |
| <p> |
| Next: <a href="Target-Options.html#Target-Options" accesskey="n" rel="next">Target Options</a>, Previous: <a href="Directory-Options.html#Directory-Options" accesskey="p" rel="prev">Directory Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
| </div> |
| <hr> |
| <a name="Specifying-subprocesses-and-the-switches-to-pass-to-them"></a> |
| <h3 class="section">3.15 Specifying subprocesses and the switches to pass to them</h3> |
| <a name="index-Spec-Files"></a> |
| |
| <p><code>gcc</code> 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 <em>spec strings</em>. 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 <samp>-specs=</samp> command-line switch to specify |
| a spec file. |
| </p> |
| <p><em>Spec files</em> 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: |
| </p> |
| <dl compact="compact"> |
| <dt><code>%<var>command</var></code></dt> |
| <dd><p>Issues a <var>command</var> to the spec file processor. The commands that can |
| appear here are: |
| </p> |
| <dl compact="compact"> |
| <dt><code>%include <<var>file</var>></code></dt> |
| <dd><a name="index-_0025include"></a> |
| <p>Search for <var>file</var> and insert its text at the current point in the |
| specs file. |
| </p> |
| </dd> |
| <dt><code>%include_noerr <<var>file</var>></code></dt> |
| <dd><a name="index-_0025include_005fnoerr"></a> |
| <p>Just like ‘<samp>%include</samp>’, but do not generate an error message if the include |
| file cannot be found. |
| </p> |
| </dd> |
| <dt><code>%rename <var>old_name</var> <var>new_name</var></code></dt> |
| <dd><a name="index-_0025rename"></a> |
| <p>Rename the spec string <var>old_name</var> to <var>new_name</var>. |
| </p> |
| </dd> |
| </dl> |
| |
| </dd> |
| <dt><code>*[<var>spec_name</var>]:</code></dt> |
| <dd><p>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>+</samp>’ |
| character, in which case the text is appended to the spec. |
| </p> |
| </dd> |
| <dt><code>[<var>suffix</var>]:</code></dt> |
| <dd><p>Creates a new ‘<samp>[<var>suffix</var>] spec</samp>’ 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: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">.ZZ: |
| z-compile -input %i |
| </pre></div> |
| |
| <p>This says that any input file whose name ends in ‘<samp>.ZZ</samp>’ should be |
| passed to the program ‘<samp>z-compile</samp>’, which should be invoked with the |
| command-line switch <samp>-input</samp> and with the result of performing the |
| ‘<samp>%i</samp>’ substitution. (See below.) |
| </p> |
| <p>As an alternative to providing a spec string, the text following a |
| suffix directive can be one of the following: |
| </p> |
| <dl compact="compact"> |
| <dt><code>@<var>language</var></code></dt> |
| <dd><p>This says that the suffix is an alias for a known <var>language</var>. This is |
| similar to using the <samp>-x</samp> command-line switch to GCC to specify a |
| language explicitly. For example: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">.ZZ: |
| @c++ |
| </pre></div> |
| |
| <p>Says that .ZZ files are, in fact, C++ source files. |
| </p> |
| </dd> |
| <dt><code>#<var>name</var></code></dt> |
| <dd><p>This causes an error messages saying: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample"><var>name</var> compiler not installed on this system. |
| </pre></div> |
| </dd> |
| </dl> |
| |
| <p>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. |
| </p> |
| </dd> |
| </dl> |
| |
| <p>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. |
| </p> |
| <div class="smallexample"> |
| <pre class="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</code> is signed |
| by default |
| startfile Object files to include at the start of the link |
| </pre></div> |
| |
| <p>Here is a small example of a spec file: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%rename lib old_lib |
| |
| *lib: |
| --start-group -lgcc -lc -leval1 --end-group %(old_lib) |
| </pre></div> |
| |
| <p>This example renames the spec called ‘<samp>lib</samp>’ to ‘<samp>old_lib</samp>’ and |
| then overrides the previous definition of ‘<samp>lib</samp>’ with a new one. |
| The new definition adds in some extra command-line options before |
| including the text of the old definition. |
| </p> |
| <p><em>Spec strings</em> are a list of command-line options to be passed to their |
| corresponding program. In addition, the spec strings can contain |
| ‘<samp>%</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. |
| </p> |
| <p>Here is a table of all defined ‘<samp>%</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. |
| </p> |
| <dl compact="compact"> |
| <dt><code>%%</code></dt> |
| <dd><p>Substitute one ‘<samp>%</samp>’ into the program name or argument. |
| </p> |
| </dd> |
| <dt><code>%i</code></dt> |
| <dd><p>Substitute the name of the input file being processed. |
| </p> |
| </dd> |
| <dt><code>%b</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>%B</code></dt> |
| <dd><p>This is the same as ‘<samp>%b</samp>’, but include the file suffix (text after |
| the last period). |
| </p> |
| </dd> |
| <dt><code>%d</code></dt> |
| <dd><p>Marks the argument containing or following the ‘<samp>%d</samp>’ as a |
| temporary file name, so that that file is deleted if GCC exits |
| successfully. Unlike ‘<samp>%g</samp>’, this contributes no text to the |
| argument. |
| </p> |
| </dd> |
| <dt><code>%g<var>suffix</var></code></dt> |
| <dd><p>Substitute a file name that has suffix <var>suffix</var> and is chosen |
| once per compilation, and mark the argument in the same way as |
| ‘<samp>%d</samp>’. 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 … %g.o … %g.s</samp>’ |
| might turn into ‘<samp>ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s</samp>’. <var>suffix</var> matches |
| the regexp ‘<samp>[.A-Za-z]*</samp>’ or the special string ‘<samp>%O</samp>’, which is |
| treated exactly as if ‘<samp>%O</samp>’ had been preprocessed. Previously, ‘<samp>%g</samp>’ |
| 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. |
| </p> |
| </dd> |
| <dt><code>%u<var>suffix</var></code></dt> |
| <dd><p>Like ‘<samp>%g</samp>’, but generates a new temporary file name |
| each time it appears instead of once per compilation. |
| </p> |
| </dd> |
| <dt><code>%U<var>suffix</var></code></dt> |
| <dd><p>Substitutes the last file name generated with ‘<samp>%u<var>suffix</var></samp>’, generating a |
| new one if there is no such last file name. In the absence of any |
| ‘<samp>%u<var>suffix</var></samp>’, this is just like ‘<samp>%g<var>suffix</var></samp>’, except they don’t share |
| the same suffix <em>space</em>, so ‘<samp>%g.s … %U.s … %g.s … %U.s</samp>’ |
| involves the generation of two distinct file names, one |
| for each ‘<samp>%g.s</samp>’ and another for each ‘<samp>%U.s</samp>’. Previously, ‘<samp>%U</samp>’ was |
| simply substituted with a file name chosen for the previous ‘<samp>%u</samp>’, |
| without regard to any appended suffix. |
| </p> |
| </dd> |
| <dt><code>%j<var>suffix</var></code></dt> |
| <dd><p>Substitutes the name of the <code>HOST_BIT_BUCKET</code>, if any, and if it is |
| writable, and if <samp>-save-temps</samp> is not used; |
| otherwise, substitute the name |
| of a temporary file, just like ‘<samp>%u</samp>’. This temporary file is not |
| meant for communication between processes, but rather as a junk |
| disposal mechanism. |
| </p> |
| </dd> |
| <dt><code>%|<var>suffix</var></code></dt> |
| <dt><code>%m<var>suffix</var></code></dt> |
| <dd><p>Like ‘<samp>%g</samp>’, except if <samp>-pipe</samp> is in effect. In that case |
| ‘<samp>%|</samp>’ substitutes a single dash and ‘<samp>%m</samp>’ 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</code>}</samp>’ |
| construct: see for example <samp>f/lang-specs.h</samp>. |
| </p> |
| </dd> |
| <dt><code>%.<var>SUFFIX</var></code></dt> |
| <dd><p>Substitutes <var>.SUFFIX</var> for the suffixes of a matched switch’s args |
| when it is subsequently output with ‘<samp>%*</samp>’. <var>SUFFIX</var> is |
| terminated by the next space or %. |
| </p> |
| </dd> |
| <dt><code>%w</code></dt> |
| <dd><p>Marks the argument containing or following the ‘<samp>%w</samp>’ as the |
| designated output file of this compilation. This puts the argument |
| into the sequence of arguments that ‘<samp>%o</samp>’ substitutes. |
| </p> |
| </dd> |
| <dt><code>%o</code></dt> |
| <dd><p>Substitutes the names of all the output files, with spaces |
| automatically placed around them. You should write spaces |
| around the ‘<samp>%o</samp>’ as well or the results are undefined. |
| ‘<samp>%o</samp>’ 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. |
| </p> |
| </dd> |
| <dt><code>%O</code></dt> |
| <dd><p>Substitutes the suffix for object files. Note that this is |
| handled specially when it immediately follows ‘<samp>%g, %u, or %U</samp>’, |
| because of the need for those to form complete file names. The |
| handling is such that ‘<samp>%O</samp>’ is treated exactly as if it had already |
| been substituted, except that ‘<samp>%g, %u, and %U</samp>’ do not currently |
| support additional <var>suffix</var> characters following ‘<samp>%O</samp>’ as they do |
| following, for example, ‘<samp>.o</samp>’. |
| </p> |
| </dd> |
| <dt><code>%p</code></dt> |
| <dd><p>Substitutes the standard macro predefinitions for the |
| current target machine. Use this when running <code>cpp</code>. |
| </p> |
| </dd> |
| <dt><code>%P</code></dt> |
| <dd><p>Like ‘<samp>%p</samp>’, but puts ‘<samp>__</samp>’ before and after the name of each |
| predefined macro, except for macros that start with ‘<samp>__</samp>’ or with |
| ‘<samp>_<var>L</var></samp>’, where <var>L</var> is an uppercase letter. This is for ISO |
| C. |
| </p> |
| </dd> |
| <dt><code>%I</code></dt> |
| <dd><p>Substitute any of <samp>-iprefix</samp> (made from <code>GCC_EXEC_PREFIX</code>), |
| <samp>-isysroot</samp> (made from <code>TARGET_SYSTEM_ROOT</code>), |
| <samp>-isystem</samp> (made from <code>COMPILER_PATH</code> and <samp>-B</samp> options) |
| and <samp>-imultilib</samp> as necessary. |
| </p> |
| </dd> |
| <dt><code>%s</code></dt> |
| <dd><p>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. |
| </p> |
| </dd> |
| <dt><code>%T</code></dt> |
| <dd><p>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 <samp>--script</samp> 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. |
| </p> |
| </dd> |
| <dt><code>%e<var>str</var></code></dt> |
| <dd><p>Print <var>str</var> as an error message. <var>str</var> is terminated by a newline. |
| Use this when inconsistent options are detected. |
| </p> |
| </dd> |
| <dt><code>%(<var>name</var>)</code></dt> |
| <dd><p>Substitute the contents of spec string <var>name</var> at this point. |
| </p> |
| </dd> |
| <dt><code>%x{<var>option</var>}</code></dt> |
| <dd><p>Accumulate an option for ‘<samp>%X</samp>’. |
| </p> |
| </dd> |
| <dt><code>%X</code></dt> |
| <dd><p>Output the accumulated linker options specified by <samp>-Wl</samp> or a ‘<samp>%x</samp>’ |
| spec string. |
| </p> |
| </dd> |
| <dt><code>%Y</code></dt> |
| <dd><p>Output the accumulated assembler options specified by <samp>-Wa</samp>. |
| </p> |
| </dd> |
| <dt><code>%Z</code></dt> |
| <dd><p>Output the accumulated preprocessor options specified by <samp>-Wp</samp>. |
| </p> |
| </dd> |
| <dt><code>%a</code></dt> |
| <dd><p>Process the <code>asm</code> spec. This is used to compute the |
| switches to be passed to the assembler. |
| </p> |
| </dd> |
| <dt><code>%A</code></dt> |
| <dd><p>Process the <code>asm_final</code> spec. This is a spec string for |
| passing switches to an assembler post-processor, if such a program is |
| needed. |
| </p> |
| </dd> |
| <dt><code>%l</code></dt> |
| <dd><p>Process the <code>link</code> 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</samp>’ sequences. |
| </p> |
| </dd> |
| <dt><code>%D</code></dt> |
| <dd><p>Dump out a <samp>-L</samp> 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. |
| </p> |
| </dd> |
| <dt><code>%L</code></dt> |
| <dd><p>Process the <code>lib</code> spec. This is a spec string for deciding which |
| libraries are included on the command line to the linker. |
| </p> |
| </dd> |
| <dt><code>%G</code></dt> |
| <dd><p>Process the <code>libgcc</code> spec. This is a spec string for deciding |
| which GCC support library is included on the command line to the linker. |
| </p> |
| </dd> |
| <dt><code>%S</code></dt> |
| <dd><p>Process the <code>startfile</code> 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 <samp>crt0.o</samp>. |
| </p> |
| </dd> |
| <dt><code>%E</code></dt> |
| <dd><p>Process the <code>endfile</code> spec. This is a spec string that specifies |
| the last object files that are passed to the linker. |
| </p> |
| </dd> |
| <dt><code>%C</code></dt> |
| <dd><p>Process the <code>cpp</code> spec. This is used to construct the arguments |
| to be passed to the C preprocessor. |
| </p> |
| </dd> |
| <dt><code>%1</code></dt> |
| <dd><p>Process the <code>cc1</code> spec. This is used to construct the options to be |
| passed to the actual C compiler (‘<samp>cc1</samp>’). |
| </p> |
| </dd> |
| <dt><code>%2</code></dt> |
| <dd><p>Process the <code>cc1plus</code> spec. This is used to construct the options to be |
| passed to the actual C++ compiler (‘<samp>cc1plus</samp>’). |
| </p> |
| </dd> |
| <dt><code>%*</code></dt> |
| <dd><p>Substitute the variable part of a matched option. See below. |
| Note that each comma in the substituted string is replaced by |
| a single space. |
| </p> |
| </dd> |
| <dt><code>%<<code>S</code></code></dt> |
| <dd><p>Remove all occurrences of <code>-S</code> from the command line. Note—this |
| command is position dependent. ‘<samp>%</samp>’ commands in the spec string |
| before this one see <code>-S</code>, ‘<samp>%</samp>’ commands in the spec string |
| after this one do not. |
| </p> |
| </dd> |
| <dt><code>%:<var>function</var>(<var>args</var>)</code></dt> |
| <dd><p>Call the named function <var>function</var>, passing it <var>args</var>. |
| <var>args</var> 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. |
| </p> |
| <p>The following built-in spec functions are provided: |
| </p> |
| <dl compact="compact"> |
| <dt><code><code>getenv</code></code></dt> |
| <dd><p>The <code>getenv</code> 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 <code>TOPDIR</code> is defined as <samp>/path/to/top</samp>, then: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%:getenv(TOPDIR /include) |
| </pre></div> |
| |
| <p>expands to <samp>/path/to/top/include</samp>. |
| </p> |
| </dd> |
| <dt><code><code>if-exists</code></code></dt> |
| <dd><p>The <code>if-exists</code> spec function takes one argument, an absolute |
| pathname to a file. If the file exists, <code>if-exists</code> returns the |
| pathname. Here is a small example of its usage: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">*startfile: |
| crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s |
| </pre></div> |
| |
| </dd> |
| <dt><code><code>if-exists-else</code></code></dt> |
| <dd><p>The <code>if-exists-else</code> spec function is similar to the <code>if-exists</code> |
| 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</code> |
| returns the pathname. If it does not exist, it returns the second argument. |
| This way, <code>if-exists-else</code> can be used to select one file or another, |
| based on the existence of the first. Here is a small example of its usage: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">*startfile: |
| crt0%O%s %:if-exists(crti%O%s) \ |
| %:if-exists-else(crtbeginT%O%s crtbegin%O%s) |
| </pre></div> |
| |
| </dd> |
| <dt><code><code>replace-outfile</code></code></dt> |
| <dd><p>The <code>replace-outfile</code> 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: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%{fgnu-runtime:%:replace-outfile(-lobjc -lobjc-gnu)} |
| </pre></div> |
| |
| </dd> |
| <dt><code><code>remove-outfile</code></code></dt> |
| <dd><p>The <code>remove-outfile</code> 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: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%:remove-outfile(-lm) |
| </pre></div> |
| |
| </dd> |
| <dt><code><code>pass-through-libs</code></code></dt> |
| <dd><p>The <code>pass-through-libs</code> spec function takes any number of arguments. It |
| finds any <samp>-l</samp> options and any non-options ending in <samp>.a</samp> (which it |
| assumes are the names of linker input library archive files) and returns a |
| result containing all the found arguments each prepended by |
| <samp>-plugin-opt=-pass-through=</samp> and joined by spaces. This list is |
| intended to be passed to the LTO linker plugin. |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%:pass-through-libs(%G %L %G) |
| </pre></div> |
| |
| </dd> |
| <dt><code><code>print-asm-header</code></code></dt> |
| <dd><p>The <code>print-asm-header</code> function takes no arguments and simply |
| prints a banner like: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">Assembler options |
| ================= |
| |
| Use "-Wa,OPTION" to pass "OPTION" to the assembler. |
| </pre></div> |
| |
| <p>It is used to separate compiler options from assembler options |
| in the <samp>--target-help</samp> output. |
| </p></dd> |
| </dl> |
| |
| </dd> |
| <dt><code>%{<code>S</code>}</code></dt> |
| <dd><p>Substitutes the <code>-S</code> 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}</samp>’ matches the command-line option <samp>-foo</samp> |
| and outputs the command-line option <samp>-foo</samp>. |
| </p> |
| </dd> |
| <dt><code>%W{<code>S</code>}</code></dt> |
| <dd><p>Like %{<code>S</code>} but mark last argument supplied within as a file to be |
| deleted on failure. |
| </p> |
| </dd> |
| <dt><code>%{<code>S</code>*}</code></dt> |
| <dd><p>Substitutes all the switches specified to GCC whose names start |
| with <code>-S</code>, but which also take an argument. This is used for |
| switches like <samp>-o</samp>, <samp>-D</samp>, <samp>-I</samp>, etc. |
| GCC considers <samp>-o foo</samp> as being |
| one switch whose name starts with ‘<samp>o</samp>’. %{o*} substitutes this |
| text, including the space. Thus two arguments are generated. |
| </p> |
| </dd> |
| <dt><code>%{<code>S</code>*&<code>T</code>*}</code></dt> |
| <dd><p>Like %{<code>S</code>*}, but preserve order of <code>S</code> and <code>T</code> options |
| (the order of <code>S</code> and <code>T</code> 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*}</samp>’. |
| </p> |
| </dd> |
| <dt><code>%{<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if the <samp>-S</samp> switch is given to GCC. |
| </p> |
| </dd> |
| <dt><code>%{!<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if the <samp>-S</samp> switch is <em>not</em> given to GCC. |
| </p> |
| </dd> |
| <dt><code>%{<code>S</code>*:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code> if one or more switches whose names start with |
| <code>-S</code> are specified to GCC. Normally <code>X</code> is substituted only |
| once, no matter how many such switches appeared. However, if <code>%*</code> |
| appears somewhere in <code>X</code>, then <code>X</code> is substituted once |
| for each matching switch, with the <code>%*</code> replaced by the part of |
| that switch matching the <code>*</code>. |
| </p> |
| <p>If <code>%*</code> appears as the last part of a spec sequence then a space |
| will be added after the end of the last substitution. If there is more |
| text in the sequence however then a space will not be generated. This |
| allows the <code>%*</code> substitution to be used as part of a larger |
| string. For example, a spec string like this: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%{mcu=*:--script=%*/memory.ld} |
| </pre></div> |
| |
| <p>when matching an option like <code>-mcu=newchip</code> will produce: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">--script=newchip/memory.ld |
| </pre></div> |
| |
| </dd> |
| <dt><code>%{.<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if processing a file with suffix <code>S</code>. |
| </p> |
| </dd> |
| <dt><code>%{!.<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if <em>not</em> processing a file with suffix <code>S</code>. |
| </p> |
| </dd> |
| <dt><code>%{,<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if processing a file for language <code>S</code>. |
| </p> |
| </dd> |
| <dt><code>%{!,<code>S</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code>, if not processing a file for language <code>S</code>. |
| </p> |
| </dd> |
| <dt><code>%{<code>S</code>|<code>P</code>:<code>X</code>}</code></dt> |
| <dd><p>Substitutes <code>X</code> if either <code>-S</code> or <code>-P</code> is given to |
| GCC. This may be combined with ‘<samp>!</samp>’, ‘<samp>.</samp>’, ‘<samp>,</samp>’, and |
| <code>*</code> sequences as well, although they have a stronger binding than |
| the ‘<samp>|</samp>’. If <code>%*</code> appears in <code>X</code>, all of the |
| alternatives must be starred, and only the first matching alternative |
| is substituted. |
| </p> |
| <p>For example, a spec string like this: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">%{.c:-foo} %{!.c:-bar} %{.c|d:-baz} %{!.c|d:-boggle} |
| </pre></div> |
| |
| <p>outputs the following command-line options from the following input |
| command-line options: |
| </p> |
| <div class="smallexample"> |
| <pre class="smallexample">fred.c -foo -baz |
| jim.d -bar -boggle |
| -d fred.c -foo -baz -boggle |
| -d jim.d -bar -baz -boggle |
| </pre></div> |
| |
| </dd> |
| <dt><code>%{S:X; T:Y; :D}</code></dt> |
| <dd> |
| <p>If <code>S</code> is given to GCC, substitutes <code>X</code>; else if <code>T</code> is |
| given to GCC, substitutes <code>Y</code>; else substitutes <code>D</code>. There can |
| be as many clauses as you need. This may be combined with <code>.</code>, |
| <code>,</code>, <code>!</code>, <code>|</code>, and <code>*</code> as needed. |
| </p> |
| |
| </dd> |
| </dl> |
| |
| <p>The conditional text <code>X</code> in a %{<code>S</code>:<code>X</code>} or similar |
| construct may contain other nested ‘<samp>%</samp>’ constructs or spaces, or |
| even newlines. They are processed as usual, as described above. |
| Trailing white space in <code>X</code> is ignored. White space may also |
| appear anywhere on the left side of the colon in these constructs, |
| except between <code>.</code> or <code>*</code> and the corresponding word. |
| </p> |
| <p>The <samp>-O</samp>, <samp>-f</samp>, <samp>-m</samp>, and <samp>-W</samp> switches are |
| handled specifically in these constructs. If another value of |
| <samp>-O</samp> or the negated form of a <samp>-f</samp>, <samp>-m</samp>, or |
| <samp>-W</samp> switch is found later in the command line, the earlier |
| switch value is ignored, except with {<code>S</code>*} where <code>S</code> is |
| just one letter, which passes all matching options. |
| </p> |
| <p>The character ‘<samp>|</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 <samp>-pipe</samp> is specified. |
| </p> |
| <p>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). |
| </p> |
| <p>GCC also knows implicitly that arguments starting in <samp>-l</samp> are to be |
| treated as compiler output files, and passed to the linker in their |
| proper position among the other output files. |
| </p> |
| |
| <hr> |
| <div class="header"> |
| <p> |
| Next: <a href="Target-Options.html#Target-Options" accesskey="n" rel="next">Target Options</a>, Previous: <a href="Directory-Options.html#Directory-Options" accesskey="p" rel="prev">Directory Options</a>, Up: <a href="Invoking-GCC.html#Invoking-GCC" accesskey="u" rel="up">Invoking GCC</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Option-Index.html#Option-Index" title="Index" rel="index">Index</a>]</p> |
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