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<h4 class="subsection">3.17.10 Darwin Options</h4>
<p><a name="index-Darwin-options-1528"></a>
These options are defined for all architectures running the Darwin operating
system.
<p>FSF GCC on Darwin does not create “fat” object files; it creates
an object file for the single architecture that GCC was built to
target. Apple's GCC on Darwin does create “fat” files if multiple
<samp><span class="option">-arch</span></samp> options are used; it does so by running the compiler or
linker multiple times and joining the results together with
<samp><span class="file">lipo</span></samp>.
<p>The subtype of the file created (like ‘<samp><span class="samp">ppc7400</span></samp>’ or ‘<samp><span class="samp">ppc970</span></samp>’ or
‘<samp><span class="samp">i686</span></samp>’) is determined by the flags that specify the ISA
that GCC is targeting, like <samp><span class="option">-mcpu</span></samp> or <samp><span class="option">-march</span></samp>. The
<samp><span class="option">-force_cpusubtype_ALL</span></samp> option can be used to override this.
<p>The Darwin tools vary in their behavior when presented with an ISA
mismatch. The assembler, <samp><span class="file">as</span></samp>, only permits instructions to
be used that are valid for the subtype of the file it is generating,
so you cannot put 64-bit instructions in a ‘<samp><span class="samp">ppc750</span></samp>’ object file.
The linker for shared libraries, <samp><span class="file">/usr/bin/libtool</span></samp>, fails
and prints an error if asked to create a shared library with a less
restrictive subtype than its input files (for instance, trying to put
a ‘<samp><span class="samp">ppc970</span></samp>’ object file in a ‘<samp><span class="samp">ppc7400</span></samp>’ library). The linker
for executables, <samp><span class="command">ld</span></samp>, quietly gives the executable the most
restrictive subtype of any of its input files.
<dl>
<dt><code>-F</code><var>dir</var><dd><a name="index-F-1529"></a>Add the framework directory <var>dir</var> to the head of the list of
directories to be searched for header files. These directories are
interleaved with those specified by <samp><span class="option">-I</span></samp> options and are
scanned in a left-to-right order.
<p>A framework directory is a directory with frameworks in it. A
framework is a directory with a <samp><span class="file">Headers</span></samp> and/or
<samp><span class="file">PrivateHeaders</span></samp> directory contained directly in it that ends
in <samp><span class="file">.framework</span></samp>. The name of a framework is the name of this
directory excluding the <samp><span class="file">.framework</span></samp>. Headers associated with
the framework are found in one of those two directories, with
<samp><span class="file">Headers</span></samp> being searched first. A subframework is a framework
directory that is in a framework's <samp><span class="file">Frameworks</span></samp> directory.
Includes of subframework headers can only appear in a header of a
framework that contains the subframework, or in a sibling subframework
header. Two subframeworks are siblings if they occur in the same
framework. A subframework should not have the same name as a
framework; a warning is issued if this is violated. Currently a
subframework cannot have subframeworks; in the future, the mechanism
may be extended to support this. The standard frameworks can be found
in <samp><span class="file">/System/Library/Frameworks</span></samp> and
<samp><span class="file">/Library/Frameworks</span></samp>. An example include looks like
<code>#include <Framework/header.h></code>, where <samp><span class="file">Framework</span></samp> denotes
the name of the framework and <samp><span class="file">header.h</span></samp> is found in the
<samp><span class="file">PrivateHeaders</span></samp> or <samp><span class="file">Headers</span></samp> directory.
<br><dt><code>-iframework</code><var>dir</var><dd><a name="index-iframework-1530"></a>Like <samp><span class="option">-F</span></samp> except the directory is a treated as a system
directory. The main difference between this <samp><span class="option">-iframework</span></samp> and
<samp><span class="option">-F</span></samp> is that with <samp><span class="option">-iframework</span></samp> the compiler does not
warn about constructs contained within header files found via
<var>dir</var>. This option is valid only for the C family of languages.
<br><dt><code>-gused</code><dd><a name="index-gused-1531"></a>Emit debugging information for symbols that are used. For stabs
debugging format, this enables <samp><span class="option">-feliminate-unused-debug-symbols</span></samp>.
This is by default ON.
<br><dt><code>-gfull</code><dd><a name="index-gfull-1532"></a>Emit debugging information for all symbols and types.
<br><dt><code>-mmacosx-version-min=</code><var>version</var><dd>The earliest version of MacOS X that this executable will run on
is <var>version</var>. Typical values of <var>version</var> include <code>10.1</code>,
<code>10.2</code>, and <code>10.3.9</code>.
<p>If the compiler was built to use the system's headers by default,
then the default for this option is the system version on which the
compiler is running, otherwise the default is to make choices that
are compatible with as many systems and code bases as possible.
<br><dt><code>-mkernel</code><dd><a name="index-mkernel-1533"></a>Enable kernel development mode. The <samp><span class="option">-mkernel</span></samp> option sets
<samp><span class="option">-static</span></samp>, <samp><span class="option">-fno-common</span></samp>, <samp><span class="option">-fno-use-cxa-atexit</span></samp>,
<samp><span class="option">-fno-exceptions</span></samp>, <samp><span class="option">-fno-non-call-exceptions</span></samp>,
<samp><span class="option">-fapple-kext</span></samp>, <samp><span class="option">-fno-weak</span></samp> and <samp><span class="option">-fno-rtti</span></samp> where
applicable. This mode also sets <samp><span class="option">-mno-altivec</span></samp>,
<samp><span class="option">-msoft-float</span></samp>, <samp><span class="option">-fno-builtin</span></samp> and
<samp><span class="option">-mlong-branch</span></samp> for PowerPC targets.
<br><dt><code>-mone-byte-bool</code><dd><a name="index-mone_002dbyte_002dbool-1534"></a>Override the defaults for <code>bool</code> so that <code>sizeof(bool)==1</code>.
By default <code>sizeof(bool)</code> is <code>4</code> when compiling for
Darwin/PowerPC and <code>1</code> when compiling for Darwin/x86, so this
option has no effect on x86.
<p><strong>Warning:</strong> The <samp><span class="option">-mone-byte-bool</span></samp> switch causes GCC
to generate code that is not binary compatible with code generated
without that switch. Using this switch may require recompiling all
other modules in a program, including system libraries. Use this
switch to conform to a non-default data model.
<br><dt><code>-mfix-and-continue</code><dt><code>-ffix-and-continue</code><dt><code>-findirect-data</code><dd><a name="index-mfix_002dand_002dcontinue-1535"></a><a name="index-ffix_002dand_002dcontinue-1536"></a><a name="index-findirect_002ddata-1537"></a>Generate code suitable for fast turnaround development, such as to
allow GDB to dynamically load <samp><span class="file">.o</span></samp> files into already-running
programs. <samp><span class="option">-findirect-data</span></samp> and <samp><span class="option">-ffix-and-continue</span></samp>
are provided for backwards compatibility.
<br><dt><code>-all_load</code><dd><a name="index-all_005fload-1538"></a>Loads all members of static archive libraries.
See man ld(1) for more information.
<br><dt><code>-arch_errors_fatal</code><dd><a name="index-arch_005ferrors_005ffatal-1539"></a>Cause the errors having to do with files that have the wrong architecture
to be fatal.
<br><dt><code>-bind_at_load</code><dd><a name="index-bind_005fat_005fload-1540"></a>Causes the output file to be marked such that the dynamic linker will
bind all undefined references when the file is loaded or launched.
<br><dt><code>-bundle</code><dd><a name="index-bundle-1541"></a>Produce a Mach-o bundle format file.
See man ld(1) for more information.
<br><dt><code>-bundle_loader </code><var>executable</var><dd><a name="index-bundle_005floader-1542"></a>This option specifies the <var>executable</var> that will load the build
output file being linked. See man ld(1) for more information.
<br><dt><code>-dynamiclib</code><dd><a name="index-dynamiclib-1543"></a>When passed this option, GCC produces a dynamic library instead of
an executable when linking, using the Darwin <samp><span class="file">libtool</span></samp> command.
<br><dt><code>-force_cpusubtype_ALL</code><dd><a name="index-force_005fcpusubtype_005fALL-1544"></a>This causes GCC's output file to have the ‘<samp><span class="samp">ALL</span></samp>’ subtype, instead of
one controlled by the <samp><span class="option">-mcpu</span></samp> or <samp><span class="option">-march</span></samp> option.
<br><dt><code>-allowable_client </code><var>client_name</var><dt><code>-client_name</code><dt><code>-compatibility_version</code><dt><code>-current_version</code><dt><code>-dead_strip</code><dt><code>-dependency-file</code><dt><code>-dylib_file</code><dt><code>-dylinker_install_name</code><dt><code>-dynamic</code><dt><code>-exported_symbols_list</code><dt><code>-filelist</code><dt><code>-flat_namespace</code><dt><code>-force_flat_namespace</code><dt><code>-headerpad_max_install_names</code><dt><code>-image_base</code><dt><code>-init</code><dt><code>-install_name</code><dt><code>-keep_private_externs</code><dt><code>-multi_module</code><dt><code>-multiply_defined</code><dt><code>-multiply_defined_unused</code><dt><code>-noall_load</code><dt><code>-no_dead_strip_inits_and_terms</code><dt><code>-nofixprebinding</code><dt><code>-nomultidefs</code><dt><code>-noprebind</code><dt><code>-noseglinkedit</code><dt><code>-pagezero_size</code><dt><code>-prebind</code><dt><code>-prebind_all_twolevel_modules</code><dt><code>-private_bundle</code><dt><code>-read_only_relocs</code><dt><code>-sectalign</code><dt><code>-sectobjectsymbols</code><dt><code>-whyload</code><dt><code>-seg1addr</code><dt><code>-sectcreate</code><dt><code>-sectobjectsymbols</code><dt><code>-sectorder</code><dt><code>-segaddr</code><dt><code>-segs_read_only_addr</code><dt><code>-segs_read_write_addr</code><dt><code>-seg_addr_table</code><dt><code>-seg_addr_table_filename</code><dt><code>-seglinkedit</code><dt><code>-segprot</code><dt><code>-segs_read_only_addr</code><dt><code>-segs_read_write_addr</code><dt><code>-single_module</code><dt><code>-static</code><dt><code>-sub_library</code><dt><code>-sub_umbrella</code><dt><code>-twolevel_namespace</code><dt><code>-umbrella</code><dt><code>-undefined</code><dt><code>-unexported_symbols_list</code><dt><code>-weak_reference_mismatches</code><dt><code>-whatsloaded</code><dd><a name="index-allowable_005fclient-1545"></a><a name="index-client_005fname-1546"></a><a name="index-compatibility_005fversion-1547"></a><a name="index-current_005fversion-1548"></a><a name="index-dead_005fstrip-1549"></a><a name="index-dependency_002dfile-1550"></a><a name="index-dylib_005ffile-1551"></a><a name="index-dylinker_005finstall_005fname-1552"></a><a name="index-dynamic-1553"></a><a name="index-exported_005fsymbols_005flist-1554"></a><a name="index-filelist-1555"></a><a name="index-flat_005fnamespace-1556"></a><a name="index-force_005fflat_005fnamespace-1557"></a><a name="index-headerpad_005fmax_005finstall_005fnames-1558"></a><a name="index-image_005fbase-1559"></a><a name="index-init-1560"></a><a name="index-install_005fname-1561"></a><a name="index-keep_005fprivate_005fexterns-1562"></a><a name="index-multi_005fmodule-1563"></a><a name="index-multiply_005fdefined-1564"></a><a name="index-multiply_005fdefined_005funused-1565"></a><a name="index-noall_005fload-1566"></a><a name="index-no_005fdead_005fstrip_005finits_005fand_005fterms-1567"></a><a name="index-nofixprebinding-1568"></a><a name="index-nomultidefs-1569"></a><a name="index-noprebind-1570"></a><a name="index-noseglinkedit-1571"></a><a name="index-pagezero_005fsize-1572"></a><a name="index-prebind-1573"></a><a name="index-prebind_005fall_005ftwolevel_005fmodules-1574"></a><a name="index-private_005fbundle-1575"></a><a name="index-read_005fonly_005frelocs-1576"></a><a name="index-sectalign-1577"></a><a name="index-sectobjectsymbols-1578"></a><a name="index-whyload-1579"></a><a name="index-seg1addr-1580"></a><a name="index-sectcreate-1581"></a><a name="index-sectobjectsymbols-1582"></a><a name="index-sectorder-1583"></a><a name="index-segaddr-1584"></a><a name="index-segs_005fread_005fonly_005faddr-1585"></a><a name="index-segs_005fread_005fwrite_005faddr-1586"></a><a name="index-seg_005faddr_005ftable-1587"></a><a name="index-seg_005faddr_005ftable_005ffilename-1588"></a><a name="index-seglinkedit-1589"></a><a name="index-segprot-1590"></a><a name="index-segs_005fread_005fonly_005faddr-1591"></a><a name="index-segs_005fread_005fwrite_005faddr-1592"></a><a name="index-single_005fmodule-1593"></a><a name="index-static-1594"></a><a name="index-sub_005flibrary-1595"></a><a name="index-sub_005fumbrella-1596"></a><a name="index-twolevel_005fnamespace-1597"></a><a name="index-umbrella-1598"></a><a name="index-undefined-1599"></a><a name="index-unexported_005fsymbols_005flist-1600"></a><a name="index-weak_005freference_005fmismatches-1601"></a><a name="index-whatsloaded-1602"></a>These options are passed to the Darwin linker. The Darwin linker man page
describes them in detail.
</dl>
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