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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - inlines with names matching __builtin_* have entire function body removed when calling builtin"
href="https://bugs.llvm.org/show_bug.cgi?id=50322">50322</a>
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<th>Summary</th>
<td>inlines with names matching __builtin_* have entire function body removed when calling builtin
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>-New Bugs
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>keescook@chromium.org
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</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre><a href="https://godbolt.org/z/fs9q55daM">https://godbolt.org/z/fs9q55daM</a>
typedef unsigned long size_t;
void fortify_panic(void) __attribute__((noreturn));
#ifndef USE_BUILTIN
extern void *memcpy_implementation(void *p, const void *q, size_t size);
#define __underlying_memcpy memcpy_implementation
#else
#define __underlying_memcpy __builtin_memcpy
#endif
// inlines with names matching a __builtin_* have their entire
// contents ignored when the matching __builtin is called anywhere
// in the function, regardless to conditionals or outcomes.
// If this isn't named "memcpy" or it doesn't ultimately call
// "__builtin_memcpy" it will work correctly.
inline void *memcpy(void *p, const void *q, size_t size)
{
size_t p_size = __builtin_object_size(p, 0);
if (p_size < size)
fortify_panic();
if (size > 4)
__underlying_memcpy(p, q, size);
return 0;
}
static char buf[8];
void *maybe_overflow(char *src, size_t size)
{
return memcpy(buf, src, size);
}
void *always_overflow(char *src)
{
return memcpy(buf, src, 16);
}
With -DUSE_BUILTIN all of the memcpy logic vanishes.</pre>
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