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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - __uuidof at a template argument causes infinite template instantiation"
href="https://bugs.llvm.org/show_bug.cgi?id=40395">40395</a>
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<th>Summary</th>
<td>__uuidof at a template argument causes infinite template instantiation
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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>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++'17
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>mail+llvm@tzik.jp
</td>
</tr>
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<th>CC</th>
<td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
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<p>
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<pre>Extra SubstNonTypeTemplateParmExpr around __uuidof causes infinite template
instantiation.
Here is a repro below. The output contains multiple instantiation of
A<&__uuidof(B)> with different AST around __uuidof.
The AST of |piid| on the second instantiation is:
| | |-TemplateArgument expr
| | | `-ConstantExpr 0x1f94990 <line:6:26> 'const _GUID *'
| | | `-SubstNonTypeTemplateParmExpr 0x1f94970 <col:26> 'const _GUID *'
| | | `-ConstantExpr 0x1f630c8 <line:10:5, col:16> 'const _GUID *'
| | | `-UnaryOperator 0x1f630b0 <col:5, col:16> 'const _GUID *' prefix
'&' cannot overflow
| | | `-CXXUuidofExpr 0x1f63080 <col:6, col:16> 'const _GUID' lvalue
And it on the third instantiation is:
| | |-TemplateArgument expr
| | | `-ConstantExpr 0x1f97678 <line:6:26> 'const _GUID *'
| | | `-SubstNonTypeTemplateParmExpr 0x1f97658 <col:26> 'const _GUID *'
| | | `-ConstantExpr 0x1f94990 <col:26> 'const _GUID *'
| | | `-SubstNonTypeTemplateParmExpr 0x1f94970 <col:26> 'const _GUID *'
| | | `-ConstantExpr 0x1f630c8 <line:10:5, col:16> 'const _GUID *'
| | | `-UnaryOperator 0x1f630b0 <col:5, col:16> 'const _GUID *'
prefix '&' cannot overflow
| | | `-CXXUuidofExpr 0x1f63080 <col:6, col:16> 'const _GUID'
lvalue
That is, the value of __uuidof is wrapped by SubstNonTypeTemplateParmExpr
multiple times, and A<&__uuidof(B)> is instantiated for each variant of wrap
level.
$ clang++ -ftemplate-depth=3 -Xclang -ast-dump -fms-extensions -fsyntax-only
-std=c++17 foo.cc
---- foo.cc ----
struct _GUID {};
struct __declspec(uuid("{AAAAAAAA-AAAA-AAAA-AAAA-AAAAAAAAAAAA}")) B {};
template <const _GUID* piid>
struct A {
virtual void baz() { A<piid>(); }
};
void f() {
A<&__uuidof(B)>();
}
----</pre>
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