compile with clang 20.1.0 error: 'lifetimebound' attribute cannot be applied to a....

[marakew]

[5/6] D:\LLVM-20.x.x-win64\bin\clang++.exe  -isystem D:/msvc/VC/Tools/MSVC/14.43.34808/include -isystem D:/msvc/V
C/Tools/MSVC/14.43.34808/atlmfc/include -isystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/ucr
t" -isystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/shared" -isystem "D:/Program Files (x86)
/Windows Kits/10/Include/10.0.18362.0/um" -isystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/w
inrt" -O3 -DNDEBUG -std=c++20 -Xclang -flto-visibility-public-std -D_MT -Xclang --dependent-lib=libcmt -MD -MT CM
akeFiles/demo.dir/main.cpp.obj -MF CMakeFiles\demo.dir\main.cpp.obj.d @CMakeFiles\demo.dir\main.cpp.obj.modmap -o
 CMakeFiles/demo.dir/main.cpp.obj -c D:/T60/test/CMake_Modules/main.cpp
FAILED: CMakeFiles/demo.dir/main.cpp.obj
D:\LLVM-20.x.x-win64\bin\clang++.exe  -isystem D:/msvc/VC/Tools/MSVC/14.43.34808/include -isystem D:/msvc/VC/Tool
s/MSVC/14.43.34808/atlmfc/include -isystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/ucrt" -is
ystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/shared" -isystem "D:/Program Files (x86)/Windo
ws Kits/10/Include/10.0.18362.0/um" -isystem "D:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/winrt"
-O3 -DNDEBUG -std=c++20 -Xclang -flto-visibility-public-std -D_MT -Xclang --dependent-lib=libcmt -MD -MT CMakeFil
es/demo.dir/main.cpp.obj -MF CMakeFiles\demo.dir\main.cpp.obj.d @CMakeFiles\demo.dir\main.cpp.obj.modmap -o CMake
Files/demo.dir/main.cpp.obj -c D:/T60/test/CMake_Modules/main.cpp
In module 'MyModule' imported from D:/T60/test/CMake_Modules/main.cpp:1:
D:/msvc/VC/Tools/MSVC/14.43.34808/include\utility:784:6: error: 'lifetimebound' attribute cannot be applied to a
parameter of a function that returns void; did you mean 'lifetime_capture_by(X)'
  784 | void as_const(const _Ty&&) = delete;
      |      ^
1 error generated.
ninja: build stopped: subcommand failed.

is it clang issue or msvc stl ?

[StephanTLavavej]

This is very likely a bug in MSVC's STL. We haven't yet checked our implementation against Clang 20 (as VS is currently shipping Clang 19) - thanks for the heads up.

[frederick-vs-ja]

llvm/llvm-project@31b0be4 and LLVM-114203 seem related.

This is possibly a bug of Clang as we aren't applying [[clang::lifetimebound]] to that overload.

STL/stl/inc/utility

Lines 778 to 784 in fc15609

	_EXPORT_STD template <class _Ty>
	_NODISCARD _MSVC_INTRINSIC constexpr add_const_t<_Ty>& as_const(_Ty& _Val) noexcept { // view _Val through const lenses
	return _Val;
	}
	_EXPORT_STD template <class _Ty>
	void as_const(const _Ty&&) = delete;