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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 - std::call_once always segfaults on MinGW (regression 11->12)"
href="https://bugs.llvm.org/show_bug.cgi?id=50146">50146</a>
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<th>Summary</th>
<td>std::call_once always segfaults on MinGW (regression 11->12)
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Windows NT
</td>
</tr>
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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>
</tr>
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<th>Component</th>
<td>-New Bugs
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>blckcat@inbox.ru
</td>
</tr>
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<th>CC</th>
<td>htmldeveloper@gmail.com, llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
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<p>
<div>
<pre>Any use of `std::call_once` on MinGW causes a segfault. It used to work in
Clang 11, but broke in 12.
Minimal example:
#include <iostream>
#include <mutex>
int main()
{
std::once_flag flag;
std::call_once(flag, []{std::cout << "Once!\n";});
}
The clang version is: Ubuntu clang version
12.0.1-++20210423082613+072c90a863aa-1~exp1~20210423063319.76
The flags I use: clang++-12 --version --target=x86_64-w64-mingw32
--sysroot=/mingw64 -pthread -femulated-tls
The libstdc++ comes from MSYS2 GCC 10.2.0 (rev 10).
Here's what GDB says if I add `-g`:
Program received signal SIGSEGV, Segmentation fault.
0x00000001e014dc4a in ?? () from
Z:\home\holyblackcat\Sandbox\2\libgcc_s_seh-1.dll
(gdb) bt
#0 0x00000001e014dc4a in ?? () from
Z:\home\holyblackcat\Sandbox\2\libgcc_s_seh-1.dll
#1 0x00000000004015f3 in std::call_once<main::$_0> (__once=..., __f=...)
at /mingw64/include/c++/10.2.0/mutex:721
#2 0x00000000004015b5 in main () at 1.cpp:8
(gdb) f 1
#1 0x00000000004015f3 in std::call_once<main::$_0> (__once=..., __f=...)
at /mingw64/include/c++/10.2.0/mutex:721
721 __once_callable = std::__addressof(__callable);
(gdb) list
716 auto __callable = [&] {
717 std::__invoke(std::forward<_Callable>(__f),
718 std::forward<_Args>(__args)...);
719 };
720 #ifdef _GLIBCXX_HAVE_TLS
721 __once_callable = std::__addressof(__callable);
722 __once_call = []{
(*(decltype(__callable)*)__once_callable)(); };
723 #else
724 unique_lock<mutex> __functor_lock(__get_once_mutex());
725 __once_functor = __callable;</pre>
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