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<a name="Stack-Smashing-Protection"></a>
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Next: <a rel="next" accesskey="n" href="Miscellaneous-Register-Hooks.html#Miscellaneous-Register-Hooks">Miscellaneous Register Hooks</a>,
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Previous: <a rel="previous" accesskey="p" href="Tail-Calls.html#Tail-Calls">Tail Calls</a>,
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Up: <a rel="up" accesskey="u" href="Stack-and-Calling.html#Stack-and-Calling">Stack and Calling</a>
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<h4 class="subsection">17.9.14 Stack smashing protection</h4>
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<p><a name="index-stack-smashing-protection-4321"></a>
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<div class="defun">
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— Target Hook: tree <b>TARGET_STACK_PROTECT_GUARD</b> (<var>void</var>)<var><a name="index-TARGET_005fSTACK_005fPROTECT_005fGUARD-4322"></a></var><br>
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<blockquote><p>This hook returns a <code>DECL</code> node for the external variable to use
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for the stack protection guard. This variable is initialized by the
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runtime to some random value and is used to initialize the guard value
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that is placed at the top of the local stack frame. The type of this
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variable must be <code>ptr_type_node</code>.
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<p>The default version of this hook creates a variable called
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‘<samp><span class="samp">__stack_chk_guard</span></samp>’, which is normally defined in <samp><span class="file">libgcc2.c</span></samp>.
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</p></blockquote></div>
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<div class="defun">
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— Target Hook: tree <b>TARGET_STACK_PROTECT_FAIL</b> (<var>void</var>)<var><a name="index-TARGET_005fSTACK_005fPROTECT_005fFAIL-4323"></a></var><br>
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<blockquote><p>This hook returns a <code>CALL_EXPR</code> that alerts the runtime that the
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stack protect guard variable has been modified. This expression should
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involve a call to a <code>noreturn</code> function.
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<p>The default version of this hook invokes a function called
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‘<samp><span class="samp">__stack_chk_fail</span></samp>’, taking no arguments. This function is
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normally defined in <samp><span class="file">libgcc2.c</span></samp>.
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</p></blockquote></div>
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<div class="defun">
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— Common Target Hook: bool <b>TARGET_SUPPORTS_SPLIT_STACK</b> (<var>bool report, struct gcc_options *opts</var>)<var><a name="index-TARGET_005fSUPPORTS_005fSPLIT_005fSTACK-4324"></a></var><br>
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<blockquote><p>Whether this target supports splitting the stack when the options described in <var>opts</var> have been passed. This is called after options have been parsed, so the target may reject splitting the stack in some configurations. The default version of this hook returns false. If <var>report</var> is true, this function may issue a warning or error; if <var>report</var> is false, it must simply return a value
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</p></blockquote></div>
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