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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong alignment of __declspec(align)ed structs"
href="https://bugs.llvm.org/show_bug.cgi?id=48776">48776</a>
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<th>Summary</th>
<td>Wrong alignment of __declspec(align)ed structs
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>11.0
</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>
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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>C
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>ju.orth@gmail.com
</td>
</tr>
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<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Consider
__declspec(align(2)) struct X {
int a;
};
#pragma pack(1)
struct Y {
struct X x;
};
int f(void) {
return _Alignof(struct Y);
}
msvc returns 2, clang returns 4 on the x86_64-pc-windows-msvc target.
Presumably because of [1]. If a struct has _any_ alignment attribute, the
branch is taken and the overall alignment of the struct is considered required.
I do not know the actual behavior of msvc, but I figure that the fix is to
exclude RecordType fields from this branch because their required alignment is
already handled in [2]. This bug seems to have been introduced in [3].
[1]
<a href="https://github.com/llvm-mirror/clang/blob/aa231e4be75ac4759c236b755c57876f76e3cf05/lib/AST/RecordLayoutBuilder.cpp#L2447-L2449">https://github.com/llvm-mirror/clang/blob/aa231e4be75ac4759c236b755c57876f76e3cf05/lib/AST/RecordLayoutBuilder.cpp#L2447-L2449</a>
[2]
<a href="https://github.com/llvm-mirror/clang/blob/aa231e4be75ac4759c236b755c57876f76e3cf05/lib/AST/RecordLayoutBuilder.cpp#L2456-L2462">https://github.com/llvm-mirror/clang/blob/aa231e4be75ac4759c236b755c57876f76e3cf05/lib/AST/RecordLayoutBuilder.cpp#L2456-L2462</a>
[3] <a href="https://reviews.llvm.org/D4714">https://reviews.llvm.org/D4714</a></pre>
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