Compilation errors with clang on windows: error: constexpr variable 'value' must be initialized by a constant expression #1409
Description
D:\LLVM\bin\clang-cl.exe -TP -imsvcD:\Clion\vcpkg\installed\x64-windows\include /DWIN32 /D_WINDOWS /EHsc /Ob0 /Od /RTC1 -std:c++latest -MDd -Zi /clang:-Wall -Wextra -Wpedantic -Wconversion /showIncludes /FoCMakeFiles\rundll.dir\main.cpp.obj /FdCMakeFiles\rundll.dir\ -c -- D:\Clion\Project\rundll\main.cpp
In file included from D:\Clion\Project\rundll\main.cpp:1:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\fstream:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\__msvc_filebuf.hpp:12:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\streambuf:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xiosbase:11:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\system_error:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\__msvc_system_error_abi.hpp:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\cstddef:12:
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xtr1common(27,26): error: constexpr variable 'value' must be initialized by a constant expression
27 | static constexpr _Ty value = _Val;
| ^ ~~~~
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xtr1common(33,16): note: in instantiation of static data member 'std::integral_constant<int (*)(sqlite3_stmt *), &sqlite3_finalize>::value' requested here
33 | return value;
| ^
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\memory(3409,13): note: in instantiation of member function 'std::integral_constant<int (*)(sqlite3_stmt *), &sqlite3_finalize>::operator int (*)(sqlite3_stmt *)' requested here
3409 | _Mypair._Get_first()(_Mypair._Myval2);
| ^
D:\Clion\vcpkg\installed\x64-windows\include\sqlite_orm/sqlite_orm.h(13652,83): note: in instantiation of member function 'std::unique_ptr<sqlite3_stmt, std::integral_constant<int (*)(sqlite3_stmt *), &sqlite3_finalize>>::~unique_ptr' requested here
13652 | mapped_iterator(const db_objects_type& dbObjects, statement_finalizer stmt) :
| ^
In file included from D:\Clion\Project\rundll\main.cpp:1:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\fstream:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\__msvc_filebuf.hpp:12:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\streambuf:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xiosbase:11:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\system_error:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\__msvc_system_error_abi.hpp:10:
In file included from E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\cstddef:12:
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xtr1common(27,26): error: constexpr variable 'value' must be initialized by a constant expression
27 | static constexpr _Ty value = _Val;
| ^ ~~~~
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\xtr1common(33,16): note: in instantiation of static data member 'std::integral_constant<void (*)(void *), &sqlite3_free>::value' requested here
33 | return value;
| ^
E:\VS\ToolChain\VC\Tools\MSVC\14.43.34808\include\memory(3409,13): note: in instantiation of member function 'std::integral_constant<void (*)(void *), &sqlite3_free>::operator void (*)(void *)' requested here
3409 | _Mypair._Get_first()(_Mypair._Myval2);
| ^
D:\Clion\vcpkg\installed\x64-windows\include\sqlite_orm/sqlite_orm.h(14189,30): note: in instantiation of member function 'std::unique_ptr<char, std::integral_constant<void (*)(void *), &sqlite3_free>>::~unique_ptr' requested here
14189 | if (char_ptr sql{sqlite3_expanded_sql(this->stmt)}) {
| ^I found the following, and it seems that clang does not yet support constexpr constraints for a dllimport function.
llvm/llvm-project#125952
llvm/llvm-project#50900
Possible solutions:
#ifdef __clang__
struct sqlite3_finalizer {
int operator()(sqlite3_stmt *pStmt) {
return sqlite3_finalize(pStmt);
}
};
using statement_finalizer = std::unique_ptr<sqlite3_stmt, sqlite3_finalizer>;
#else
using statement_finalizer =
std::unique_ptr<sqlite3_stmt, std::integral_constant<decltype(&sqlite3_finalize), sqlite3_finalize>>;
#endif#ifdef __clang__
struct sqlite3_freer {
void operator()(void* ptr) {
sqlite3_free(ptr);
}
};
using char_ptr = std::unique_ptr<char, sqlite3_freer>;
#else
using char_ptr = std::unique_ptr<char, std::integral_constant<decltype(&sqlite3_free), sqlite3_free>>;
#endif