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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - clang -mkernel/-ffreestanding/-fno-builtin evaluates "__has_builtin(__builtin___memcpy_chk)" as true"
href="https://llvm.org/bugs/show_bug.cgi?id=23093">23093</a>
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<th>Summary</th>
<td>clang -mkernel/-ffreestanding/-fno-builtin evaluates "__has_builtin(__builtin___memcpy_chk)" as true
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<th>Product</th>
<td>clang
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<th>Version</th>
<td>trunk
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<th>Hardware</th>
<td>PC
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<th>OS</th>
<td>All
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<th>Status</th>
<td>NEW
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<th>Severity</th>
<td>normal
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<th>Priority</th>
<td>P
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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>ahmed.bougacha@gmail.com
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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<p>
<div>
<pre>__has_builtin currently disregards -mkernel/-ffreestanding/-fno-builtin for the
various __builtin_s. I tried with __builtin_memcpy_chk and __builtin_expect,
and they're always marked as available.
For the latter that's perfectly fine (as it is for most __builtin_s), but is it
also for the _chk functions? We provide them as builtins, but they really are
functions, so perhaps an exception is acceptable.
One alternative would be to tell users to check for freestanding/kernel, but
that's a bit contrived when there's the more descriptive __has_builtin.
$ cat builtin.c
#if __has_builtin(__builtin___memcpy_chk)
#warning "__memcpy_chk is available"
#else
#warning "__memcpy_chk is not available"
#endif
$ clang ./builtin.c -fsyntax-only -fno-builtin
./builtin.c:2:2: warning: "__memcpy_chk is available" [-W#warnings]
#warning "__memcpy_chk is available"
^
1 warning generated.</pre>
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