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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __has_declspec_attribute falsely reports some attrs as supported for MinGW and Cygwin targets"
href="https://bugs.llvm.org/show_bug.cgi?id=50614">50614</a>
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<th>Summary</th>
<td>__has_declspec_attribute falsely reports some attrs as supported for MinGW and Cygwin targets
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>12.0
</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>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
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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
</td>
</tr>
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<th>Reporter</th>
<td>xtkoba@gmail.com
</td>
</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>Created <span class=""><a href="attachment.cgi?id=24923" name="attach_24923" title="Repro">attachment 24923</a> <a href="attachment.cgi?id=24923&action=edit" title="Repro">[details]</a></span>
Repro
It is true that the warnings for this specific repro can be silenced by adding
the -fms-extensions option, but this option causes other problems in practice
(causing function redefinition errors) and so I think I cannot use it.
$ cat mingw-declspec.c
#if __has_declspec_attribute(noalias)
__declspec(noalias)
#else
#warning no declspec noalias
#endif
void foo(void *a, void *b);
struct
#if __has_declspec_attribute(align)
__declspec(align(8))
#else
#warning no declspec align
#endif
bar { int i, j; } baz;
$ clang --target=x86_64-w64-mingw32 -fdeclspec -c mingw-declspec.c
mingw-declspec.c:3:12: warning: unknown attribute 'noalias' ignored
[-Wunknown-attributes]
__declspec(noalias)
^~~~~~~
<built-in>:343:38: note: expanded from here
#define __declspec(a) __attribute__((a))
^
mingw-declspec.c:11:12: warning: unknown attribute 'align' ignored
[-Wunknown-attributes]
__declspec(align(8))
^~~~~~~~
<built-in>:343:38: note: expanded from here
#define __declspec(a) __attribute__((a))
^
2 warnings generated.</pre>
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