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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - ConvertDeclSpecToType mishandles cv-qualifiers on a function type"
href="http://llvm.org/bugs/show_bug.cgi?id=16654">16654</a>
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<th>Summary</th>
<td>ConvertDeclSpecToType mishandles cv-qualifiers on a function type
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
</tr>
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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>C++
</td>
</tr>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>james.widman@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>The following is well-formed C++11/1y, ill-formed C++2003, and
well-formed-but-with-undefined-behavior in C99:
typedef int F();
template<typename T> struct A {};
extern A<F> x;
extern A<F const > x;
extern A<F volatile > x;
extern A<F const volatile> x;
C++11 and C++1y say that the last three declarations of X are well-formed (but
redundant) because, as used above, "cv-qualifiers are ignored." [dcl.fct p6]
So in each declaration of x above, the canonical type is "A<function of ()
returning int>".
But with ToT (r186588), running:
clang++ -std=c++1y -stdlib=libc++ -pedantic -O3 -Wall -c t1.cpp
... Clang seems to behave as if the canonical type is different for each
declaration. Here's an excerpt:
--
t1.cpp:5:12: warning: qualifier on function type 'F' (aka 'int ()') has
unspecified behavior
extern A<F const > x;
~~^~~~~
t1.cpp:5:20: error: redefinition of 'x' with a different type: 'A<const F>' vs
'A<F>'
extern A<F const > x;
^
t1.cpp:4:13: note: previous definition is here
extern A<F> x;
^
The "unspecified behavior" remark is better suited to C99.
And C++2003 says the program is ill-formed for trying to cv-qualify a function
type.
The code issuing the diagnostic is ConvertDeclSpecToType() in .
I'm guessing that in lib/Sema/SemaType.cpp -> ConvertDeclSpecToType() -> "if
(Result->isFunctionType() && TypeQuals)", for C++ (all years), you would want:
TypeQuals &= ~DeclSpec::TQ_const;
.. after giving a dialect-appropriate diagnostic. (Ditto for volatile.)
For C, status quo seems good (though maybe adjust the diagnostic to mention
undefined rather than unspecified behavior).</pre>
</div>
</p>
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