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| <h3 class="section">22.7 Configuring the Current ABI</h3> |
| |
| <p><span class="sc">gdb</span> can determine the <dfn>ABI</dfn> (Application Binary Interface) of your |
| application automatically. However, sometimes you need to override its |
| conclusions. Use these commands to manage <span class="sc">gdb</span>'s view of the |
| current ABI. |
| |
| <p><a name="index-OS-ABI-1702"></a><a name="index-set-osabi-1703"></a><a name="index-show-osabi-1704"></a><a name="index-Newlib-OS-ABI-and-its-influence-on-the-longjmp-handling-1705"></a> |
| One <span class="sc">gdb</span> configuration can debug binaries for multiple operating |
| system targets, either via remote debugging or native emulation. |
| <span class="sc">gdb</span> will autodetect the <dfn>OS ABI</dfn> (Operating System ABI) in use, |
| but you can override its conclusion using the <code>set osabi</code> command. |
| One example where this is useful is in debugging of binaries which use |
| an alternate C library (e.g. <span class="sc">uClibc</span> for <span class="sc">gnu</span>/Linux) which does |
| not have the same identifying marks that the standard C library for your |
| platform provides. |
| |
| <p>When <span class="sc">gdb</span> is debugging the AArch64 architecture, it provides a |
| “Newlib” OS ABI. This is useful for handling <code>setjmp</code> and |
| <code>longjmp</code> when debugging binaries that use the <span class="sc">newlib</span> C library. |
| The “Newlib” OS ABI can be selected by <code>set osabi Newlib</code>. |
| |
| <dl> |
| <dt><code>show osabi</code><dd>Show the OS ABI currently in use. |
| |
| <br><dt><code>set osabi</code><dd>With no argument, show the list of registered available OS ABI's. |
| |
| <br><dt><code>set osabi </code><var>abi</var><dd>Set the current OS ABI to <var>abi</var>. |
| </dl> |
| |
| <p><a name="index-float-promotion-1706"></a> |
| Generally, the way that an argument of type <code>float</code> is passed to a |
| function depends on whether the function is prototyped. For a prototyped |
| (i.e. ANSI/ISO style) function, <code>float</code> arguments are passed unchanged, |
| according to the architecture's convention for <code>float</code>. For unprototyped |
| (i.e. K&R style) functions, <code>float</code> arguments are first promoted to type |
| <code>double</code> and then passed. |
| |
| <p>Unfortunately, some forms of debug information do not reliably indicate whether |
| a function is prototyped. If <span class="sc">gdb</span> calls a function that is not marked |
| as prototyped, it consults <kbd>set coerce-float-to-double</kbd>. |
| |
| |
| <a name="index-set-coerce_002dfloat_002dto_002ddouble-1707"></a> |
| <dl><dt><code>set coerce-float-to-double</code><dt><code>set coerce-float-to-double on</code><dd>Arguments of type <code>float</code> will be promoted to <code>double</code> when passed |
| to an unprototyped function. This is the default setting. |
| |
| <br><dt><code>set coerce-float-to-double off</code><dd>Arguments of type <code>float</code> will be passed directly to unprototyped |
| functions. |
| |
| <p><a name="index-show-coerce_002dfloat_002dto_002ddouble-1708"></a><br><dt><code>show coerce-float-to-double</code><dd>Show the current setting of promoting <code>float</code> to <code>double</code>. |
| </dl> |
| |
| <p><a name="index-set-cp_002dabi-1709"></a><a name="index-show-cp_002dabi-1710"></a><span class="sc">gdb</span> needs to know the ABI used for your program's C<tt>++</tt> |
| objects. The correct C<tt>++</tt> ABI depends on which C<tt>++</tt> compiler was |
| used to build your application. <span class="sc">gdb</span> only fully supports |
| programs with a single C<tt>++</tt> ABI; if your program contains code using |
| multiple C<tt>++</tt> ABI's or if <span class="sc">gdb</span> can not identify your |
| program's ABI correctly, you can tell <span class="sc">gdb</span> which ABI to use. |
| Currently supported ABI's include “gnu-v2”, for <code>g++</code> versions |
| before 3.0, “gnu-v3”, for <code>g++</code> versions 3.0 and later, and |
| “hpaCC” for the HP ANSI C<tt>++</tt> compiler. Other C<tt>++</tt> compilers may |
| use the “gnu-v2” or “gnu-v3” ABI's as well. The default setting is |
| “auto”. |
| |
| <dl> |
| <dt><code>show cp-abi</code><dd>Show the C<tt>++</tt> ABI currently in use. |
| |
| <br><dt><code>set cp-abi</code><dd>With no argument, show the list of supported C<tt>++</tt> ABI's. |
| |
| <br><dt><code>set cp-abi </code><var>abi</var><dt><code>set cp-abi auto</code><dd>Set the current C<tt>++</tt> ABI to <var>abi</var>, or return to automatic detection. |
| </dl> |
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