<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/69284>69284</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang hangs when compile attatched bug.cpp
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          pbl-pw
      </td>
    </tr>
</table>

<pre>
    # Clang hangs when compile attatched bug.cpp

command line: clang++ -std=c++20 -c bug.cpp -O3
test on msys2 ucrt64 clang and offcial LLVM win64 clang, both hangs.

emit llvm comand line `clang++ -std=c++20 -c bug.cpp -O3 -emit-llvm` ok

run `llc bug.bc` output:

``` cmd
c:/msys2/ucrt64/bin/llc.exe: error: c:/msys2/ucrt64/bin/llc.exe: bug.bc: error: Invalid cast (Producer: 'LLVM17.0.2' Reader: 'LLVM 17.0.2')
```

source bug.cpp:

``` c++
class IFunction
{
 void *_ptr;

public:
 template <typename T>
 constexpr IFunction(T &&obj) noexcept : _ptr{new void *{(void *)&ClassVTable<T>}} {}

public:
 struct TRawVTable
 {
  void (*_operatorCall)(void *);
 };

 template <typename T> // requires std::is_invocable_r_v<void, T>
 static constexpr TRawVTable ClassVTable{[](void *ptr) -> void { return (*(T *)ptr)(); /* return; ok */ }};
};

enum class TrChID : unsigned _BitInt(1) // unsigned _BitInt(2) ok
{
 A = 0,
 B = 1,
};

extern void other(TrChID chid, IFunction) noexcept;

IFunction func(TrChID chid)
{
 return [chid] { other(chid, []() -> void {}); };
}
```

msys2 clang info:

``` cmd
"c:\msys2\ucrt64\bin\clang++.exe" -std=c++20  -c bug.cpp -O3 -v
clang version 17.0.2
Target: x86_64-w64-windows-gnu
Thread model: posix
InstalledDir: c:/msys2/ucrt64/bin
 (in-process)
 "c:/msys2/ucrt64/bin/clang++.exe" -cc1 -triple x86_64-w64-windows-gnu -emit-obj -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name bug.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -mms-bitfields -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -debugger-tuning=gdb -v -fcoverage-compilation-dir=E:/Projects/bug/.Build -resource-dir c:/msys2/ucrt64/lib/clang/17 -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++ -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/backward -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0 -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0/backward -internal-isystem c:/msys2/ucrt64/include/c++/13.2.0 -internal-isystem c:/msys2/ucrt64/include/c++/13.2.0/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/include/c++/13.2.0/backward -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++ -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++/backward -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0/backward -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2/backward -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13/x86_64-w64-mingw32 -internal-isystem c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13/backward -internal-isystem c:/msys2/ucrt64/lib/clang/17/include -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/include -internal-isystem c:/msys2/ucrt64/x86_64-w64-mingw32/usr/include -internal-isystem c:/msys2/ucrt64/include -O3 -std=c++20 -fdeprecated-macro -fdebug-compilation-dir=E:/Projects/bug/.Build -ferror-limit 19 -fmessage-length=220 -femulated-tls -fno-use-cxa-atexit -fgnuc-version=4.2.1 -fno-implicit-modules -fcxx-exceptions -fexceptions -exception-model=seh -fcolor-diagnostics -vectorize-loops -vectorize-slp -faddrsig -o bug.o -x c++ bug.cpp
clang -cc1 version 17.0.2 based upon LLVM 17.0.2 default target x86_64-w64-windows-gnu
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include/c++/13.2.0/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/c++/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2.0/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13.2/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13/x86_64-w64-mingw32"
ignoring nonexistent directory "c:/msys2/ucrt64/lib/gcc/x86_64-w64-mingw32/13.2.0/include/g++-v13/backward"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/include"
ignoring nonexistent directory "c:/msys2/ucrt64/x86_64-w64-mingw32/usr/include"
#include "..." search starts here:
#include <...> search starts here:
 c:/msys2/ucrt64/include/c++/13.2.0
 c:/msys2/ucrt64/include/c++/13.2.0/x86_64-w64-mingw32
 c:/msys2/ucrt64/include/c++/13.2.0/backward
 c:/msys2/ucrt64/lib/clang/17/include
 c:/msys2/ucrt64/include
End of search list.
```

offcial LLVM win64 clang info:

``` cmd
"c:\LLVM\bin\clang++.exe" -std=c++20  -c bug.cpp -O3 -v
clang version 17.0.2
Target: x86_64-pc-windows-msvc
Thread model: posix
InstalledDir: c:\LLVM\bin
 (in-process)
 "c:\\LLVM\\bin\\clang++.exe" -cc1 -triple x86_64-pc-windows-msvc19.20.0 -emit-obj -mincremental-linker-compatible -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name bug.cpp -mrelocation-model pic -pic-level 2 -mframe-pointer=none -fmath-errno -ffp-contract=on -fno-rounding-math -mconstructor-aliases -funwind-tables=2 -target-cpu x86-64 -tune-cpu generic -v "-fcoverage-compilation-dir=E:\\Projects\\bug\\.Build" -resource-dir "c:\\LLVM\\lib\\clang\\17" -internal-isystem "c:\\LLVM\\lib\\clang\\17\\include" -internal-isystem "C:/Program Files/Microsoft Visual Studio 10.0/VC/include" -internal-isystem "C:/Program Files/Microsoft Visual Studio 9.0/VC/include" -internal-isystem "C:/Program Files/Microsoft Visual Studio 9.0/VC/PlatformSDK/Include" -internal-isystem "C:/Program Files/Microsoft Visual Studio 8/VC/include" -internal-isystem "C:/Program Files/Microsoft Visual Studio 8/VC/PlatformSDK/Include" -O3 -std=c++20 -fdeprecated-macro "-fdebug-compilation-dir=E:\\Projects\\bug\\.Build" -ferror-limit 19 -fmessage-length=220 -fno-use-cxa-atexit -fms-extensions -fms-compatibility -fms-compatibility-version=19.20 -fdelayed-template-parsing -fno-implicit-modules -fcxx-exceptions -fexceptions -fcolor-diagnostics -vectorize-loops -vectorize-slp -faddrsig -o bug.o -x c++ bug.cpp
clang -cc1 version 17.0.2 based upon LLVM 17.0.2 default target x86_64-pc-windows-msvc
ignoring nonexistent directory "C:/Program Files/Microsoft Visual Studio 10.0/VC/include"
ignoring nonexistent directory "C:/Program Files/Microsoft Visual Studio 9.0/VC/include"
ignoring nonexistent directory "C:/Program Files/Microsoft Visual Studio 9.0/VC/PlatformSDK/Include"
ignoring nonexistent directory "C:/Program Files/Microsoft Visual Studio 8/VC/include"
ignoring nonexistent directory "C:/Program Files/Microsoft Visual Studio 8/VC/PlatformSDK/Include"
#include "..." search starts here:
#include <...> search starts here:
 c:\LLVM\lib\clang\17\include
End of search list.
```

</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzkWl9v2zgS_zTMy4CGTfnvQx4SuwaK28UVu0FfA4oayWwpUkdSjnOf_kBKlp3ETtMkdnJYoI1tcjR_fkMOZ4bizslCI16S0TUZLS547VfGXlapotXdRWqy-0vCEpgrrgtYcV04uFuhBmHKSioE7j33YoUZpHXRE1VF-gvSv2r-ClOWXGegpEaSXIEIXAi7JuwaqPMZSRai-cn6QMWWBdB_Jw0Dj86D0VC6e8egFtaPhw0XCHxNngvJFfzxx_c_4U7q7SRhc0iNXzUK9_ZVwlJ6UGpdBgu2ugEZ939DN6CBCw1cyLgP5ue-AFvrwE6p5pFURJLaV7UnydU-JRn3m38gyqwFLJCwZTSXsGVjMGHLVGrClkqJHm4ikmitsRHSlz7RKrP_7Fe95kpmILjzQNj0mzVZLTDOETYJqA4mvX6PETaBv5BnD6agmyNs9siifTOdqa3AbnkcxaABu8VBcefg67LWwkujW9pJOwtrIzMg7Oq28pYk1_sMqzpVUnRSwGNZKe4RSDL39xVqXiLckORLOy-Mdh43ld2TxqY3QNiYsLFJfxA2A21wI7DyEMyPQifXGu86PYJmbNr9YjPCxvNgwvcbniokyTxKnCzIZAGBeLJ4TmfnbS083PzF71oGzfgOgK3kaQDBVGi5N3bOlYqyH2iyhQeC0IdYHQcHCFsStgSL_6mlRQdxQ1yR5Eq6W6nXRgS1bu3tmiTzIC3suD1Unedeij1wd7bAPjCT6ybs7Okc0GUzoEGLZmxyDRZ9bXVrcOufYF1DHIeDpY3aVy15GDA_G8olNOjvEHiCBuq6hGbh3dj56usiervWMT5mcHst_VftCZsOgn4tQAemWZjuYkLnsisgyQL6hM3bges4MOgGDmi08Wh1g4LxK7TB8kY1sWow31u0u2X6iE1HA3mtxWMes8eKbrEeXUeCUVyxnfyt4M5vT5wV7Gi98Qjv4zGiie9NYJc6N7-OlISxuGNG8yb0jeZt6BvNQ-gbzffieQyBjD0N60_i-roLP7qANVoXUGvjXJy54bbAEMhhMx3fjof0LvyXOjN3jha6bqlWFnkGpclQBdrKOLlpnaGd50phtpC_jN_tvmVTqWlljUDnOn_BFoCjsf8QAEIMgHorK4VHDGjPNpP-AJpJF3YpzS0iUKGQW8qdpynmxiJNufiJOtvRhQORrtHKXKKNw4LbjK65qpGG2OKAllxqmkvVDOzQLy0qI3hYpjTiBpUUQCspqMI1KmBAy9zyEmllpPbhKFpooxFoXnK_omitNkDzvKLCaG-58CRZGA0014ZaU-tM6oIGWqBljEwhyhpLuZLcRd1KR1Ppc4kqc0DzWgdgqA_GOZIsGFAf_U9FVQf86HgI1Nca40CBGm1QOsO0Lgq0YUrqgiSLIkuBroHmwqzR8gJpkz819mZhKSy-NN78Zs0PFN4FP9YFYcvedS1VBtRic5IG8qPLRsl05_rlYAI0YqW5otLdO4_l0Uf31kMpdXGXhFmphaozDDy3udE7MzxIeAopYbnecZudgvcg6bFe_3SczwZSJ-4VaL0LMKfD4L3NbbZaIcQxfDvmb9lEb5DyVsDeJvpMiLYnHF3_9kp7B2kfgfBTFT4C6XPK-nCUPwTj80n6YHzfgu4u0dlxf6dj8a1samdfxax7ItQjT_pQeYaVRcE9ZrTkwpo4lNbFKxLKPDaCqJKl9DCYhUQanQvJqUJd-FXIeKNMLGsVJXrlmnS6dkjFhlPucSM90LzQtaBtwUSSxbDHeoOGVJaVkkL6kNXXKqTZudhsaFOpSqPDwP6P7jtty6eFw1XMnJWxNJO80MZ5KRzQNYb8Xf4XqTKmejDgVAU051lmnSyAmlhoGKCbbZ_pYbuyKfhiefSw6oOUO8ygroyGvaYXZJjzWnlo6oFni0FZaGOlLiBUKxvpPGoPmbRR1_vn6riXZm3sXIIOEp5P-jZMnFPmNnadX-IHg_0kvXgH4W_KKD9W-mm88T4p9gcp8iQT_RxafB5PHU_VP4NCn0OHT-qtT-Wrz6DBp_TTOXOC07B_UCV0QghLtmUAYazX6xHGwCG3YgXOc-sdrNDi7pZkjz6ZB_rky3P0r-mRvfrBg5a_gVvn8ed5HC8QXyg8Un2JbxlssVTS-d4z11jH3kf47TutwODcN1mV6GqX0q3F626yHqj-ovur0Xz3UGfyEasPXF890now67F-r79_i1VKLSyWqD1XVEn9E20slrmXqcJ_3i3Xq6-11sFnv77Cit7rmg6NU-ui-dK0HqIvH1xnHVkMYQ_vLYb4NezkQ92p32MRP3dh9zC_eddAKSwvYSkDXmz5pxTWOJN7-C5dzRX87etMGhj0Y3z6Pn8Q0d-F9ewcnL8p7nNjy78X_yJs-fV95UxPpP_019q_sJEWF_ezvbQXruwX99UONdJKR3HjUbu2NVa6LlhJJf39gaG9vlsMf9E4xe8xo9sXfGjFrQtZy6tacv8XvbeDx9evs7V32eMnEnZw159e1rGddCLJByLDqSU9b-F5su_ukGpOqO3xFM-mV6WgF9llks2SGb_Ay8F4NhkNpoPJ4GJ1yWaz6XQ6Hs-mOEqztJ_ipD8TySQfjiY8y_iFvGR9lgz6g0l_OJwlg95kMmE4HU15PhhOxumQDPtYcql6IffpGVtcSOdqvBzP2HR4oXiKysUXiBlr0zZGRosLexlzpbQuHBn2g-Zux8FLr_Dy5e8VX9RWXa68r1zj9FAJSr-q054wZXzVdb39CMlmiNFhTQU9w5qIqv4vAAD__9q91Bc">