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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __builtin_offsetof doesn't allow scope qualifiers"
href="https://bugs.llvm.org/show_bug.cgi?id=34630">34630</a>
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<th>Summary</th>
<td>__builtin_offsetof doesn't allow scope qualifiers
</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>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>C++
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>myriachan@gmail.com
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>The following code does not compile, with a syntax error:
#include <cstddef>
struct A { int x; };
struct B { };
struct C : A, B { };
int meow()
{
return offsetof(C, A::x);
}
error: expected ')'
Whether this should be allowed in C++ is an interesting question. C++ defers
to C, which says a "member-designator" here, but then doesn't define that.
(There's a WG14 defect report somewhere on this, to be fixed for C2x?)
Normally, this wouldn't be necessary, because the first parameter should be a
standard-layout type, which can't have non-static members of conflicting names.
But pretty much every compiler supports offsetof() on everything but virtual
inheritance cases, so people use it. (Also, there's a C++ proposal in the
works to formally allow offsetof for any class not involving the word
"virtual".)
GCC allows this.</pre>
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