Bug 22323 – Link error for virtual destructor of C++ class in DLL

A C++ class with virtual destructor in a DLL can't be used from D, because a symbol is not found during linking. /////////////// testdestructor.d ///////////////// extern(C++) class C { ~this(); } void main() { C o = new C; } ///////////// testdestructorcpp.cpp ////////////// class __declspec(dllexport) C { public: virtual ~C(); }; C::~C() { } ////////////////////////////////////////////////// First I'm compiling a DLL from the C++ file: cl /LD /nologo testdestructorcpp.cpp Then I try to compile the D program using the DLL, which fails to link: dmd -m64 testdestructor.d testdestructorcpp.lib testdestructor.obj : error LNK2001: unresolved external symbol "public: virtual void * __cdecl C::`scalar deleting destructor'(unsigned int)" (??_GC@@UEAAPEAXI@Z) testdestructor.exe : fatal error LNK1120: 1 unresolved externals Error: linker exited with status 1120 It works using static linking. In the forum I found a description of the same problem: https://forum.dlang.org/thread/[email protected]

(In reply to Tim from comment #0) > It works using static linking. Then it looks like the MS compiler generates the symbol but doesn't export it even when exporting the class - or at least doesn't include the forwarder in the DLL import lib. It looks like this might be solvable by removing the condition in https://github.com/dlang/dmd/blob/0bbb30aad9a782b4e9a1cbec62704240729d7864/src/dmd/clone.d#L1069, where the D compiler only defines it in case the regular destructor is defined in D as well. The symbol would most likely need to be emitted as a weak definition though to prevent conflicts when linking statically etc.

(In reply to kinke from comment #1) > It looks like this might be solvable by removing the condition in > https://github.com/dlang/dmd/blob/0bbb30aad9a782b4e9a1cbec62704240729d7864/ > src/dmd/clone.d#L1069, where the D compiler only defines it in case the > regular destructor is defined in D as well. The symbol would most likely > need to be emitted as a weak definition though to prevent conflicts when > linking statically etc. Thanks for the suggestion. It seems to work in a first test.

@tim-dlang created dlang/dmd pull request #13148 "fix Issue 22323: Link error for virtual destructor of C++ class in DLL" fixing this issue: - fix Issue 22323: Link error for virtual destructor of C++ class in DLL The new test test/dshell/dll_cxx.d is based on test/dshell/dll.d, but builds the DLL/SO from C++ instead of D. https://github.com/dlang/dmd/pull/13148

dlang/dmd pull request #13148 "fix Issue 22323: Link error for virtual destructor of C++ class in DLL" was merged into master: - d71fd29d62bf404e887740274ee6c98e56c7bd6f by Tim Schendekehl: fix Issue 22323: Link error for virtual destructor of C++ class in DLL The new test test/dshell/dll_cxx.d is based on test/dshell/dll.d, but builds the DLL/SO from C++ instead of D. https://github.com/dlang/dmd/pull/13148

dlang/dmd pull request #13160 "fix Issue 22323: Link error for virtual destructor of C++ class in DLL" was merged into stable: - 062a2f27565b8e3dabde457757742ebc3c9af8c6 by Tim Schendekehl: fix Issue 22323: Link error for virtual destructor of C++ class in DLL The new test test/dshell/dll_cxx.d is based on test/dshell/dll.d, but builds the DLL/SO from C++ instead of D. https://github.com/dlang/dmd/pull/13160

dlang/dmd pull request #13164 "Merge stable" was merged into master: - 1e6217535f271fe9e6911bc1bf113df1a345a589 by Tim Schendekehl: fix Issue 22323: Link error for virtual destructor of C++ class in DLL The new test test/dshell/dll_cxx.d is based on test/dshell/dll.d, but builds the DLL/SO from C++ instead of D. https://github.com/dlang/dmd/pull/13164