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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Super confusing diag when overload prevents template argument inference"
href="https://bugs.llvm.org/show_bug.cgi?id=39561">39561</a>
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<th>Summary</th>
<td>Super confusing diag when overload prevents template argument inference
</td>
</tr>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</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>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++11
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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</tr>
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<th>Reporter</th>
<td>nicolasweber@gmx.de
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</tr>
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
</td>
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<div>
<pre>Someone asked me why this doesn't build:
$ cat parallel_merge_sort.cpp
#include <thread>
void mergesort(void *records, int start, int end, int threads) {
std::thread lthread(mergesort, records, start, end, threads);
};
$ clang++ -std=c++11 -c parallel_merge_sort.cpp
parallel_merge_sort.cpp:3:15: error: no matching constructor for initialization
of 'std::thread'
std::thread lthread(mergesort, records, start, end, threads);
^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:353:9:
note: candidate template ignored: couldn't infer template argument '_Fp'
thread::thread(_Fp&& __f, _Args&&... __args)
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:286:5:
note: candidate constructor not viable: requires 1 argument, but 5 were
provided
thread(const thread&);
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:309:5:
note: candidate constructor not viable: requires single argument '__t', but 5
arguments were provided
thread(thread&& __t) _NOEXCEPT : __t_(__t.__t_) {__t.__t_ = 0;}
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/thread:293:5:
note: candidate constructor not viable: requires 0 arguments, but 5 were
provided
thread() _NOEXCEPT : __t_(0) {}
^
1 error generated.
It builds fine on Windows, on Linux with libc++ and libstd++, but doesn't build
on macOS or on the BSDs.
The reason is that BSD has a function named "mergesort" in its C standard
library, which makes inference of the first thread ctor candidate fail. Our
diagnostic here could be much better.</pre>
</div>
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