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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Clang treats differently on function return type with a union"
href="https://bugs.llvm.org/show_bug.cgi?id=46645">46645</a>
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<th>Summary</th>
<td>Clang treats differently on function return type with a union
</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>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>haoxintu@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
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<pre>Hi, all.
This code, test.cc, line 1 and 2 equals to line 3 (right?). Clang treats it
differently.
$cat test.cc
typedef union{} typedef_union;
typename :: typedef_union foo1 () {}
union {} foo2 () {}
$clang++ -c -w test.cc
test.cc:3:1: error: '(anonymous union at test.cc:3:1)' cannot be defined in the
result type of a function
union {} foo2 () {}
^
1 error generated.
Clang rejects line 3 but accepts line 2.
While in GCC
$g++ -c -w test.cc
test.cc:2:13: error: ‘class’ tag used in naming ‘union typedef_union’
[-fpermissive]
2 | typename :: typedef_union foo1 () {}
| ^~~~~~~~~~~~~
test.cc:1:17: note: ‘union typedef_union’ was previously declared here
1 | typedef union{} typedef_union;
| ^~~~~~~~~~~~~
test.cc:3:1: error: new types may not be defined in a return type
3 | union {} foo2 () {}
| ^~~~~
test.cc:3:1: note: (perhaps a semicolon is missing after the definition of
‘<unnamed union>’)
GCC emits two errors in line 2 and line 3.
I guess Clang might treat the line 2 and line 3 equally. So is this a Clang's
accept-invalid bug or GCC's reject-valid?
Thanks,
Haoxin</pre>
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