c++ - 奇怪的 "invalid conversion from <type> to <type>"错误

Question

这里是输出:

g++ -DDEBUG -DUNITTEST -IC:/Users/Steven/Dropbox/Programming/entropy_p5_makefile/cpp/game/../include/ -O0 -g3 -Wall -c -fmessage-length=0 -o Input.o ..\Input.cpp
..\Input.cpp: In function 'void mousehookCustomRoutine(E_thread*, void*)':
..\Input.cpp:78:93: error: invalid conversion from 'LRESULT (*)(int, WPARAM, LPARAM)' to 'LRESULT (*)(int, WPARAM, LPARAM)'
..\Input.cpp:78:93: error:   initializing argument 2 of 'void* SetWindowsHookExA(int, LRESULT (*)(int, WPARAM, LPARAM), HINSTANCE__*, DWORD)'
Build error occurred, build is stopped

这是代码:

LRESULT CALLBACK MouseHookProc(int nCode, WPARAM wParam, LPARAM lParam) {
    //...
}

void mousehookCustomRoutine(E_thread *me, void *arg = (void *)&MouseHookProc) {
    // arg is the ptr to LL Mouse Routine

    me->sendMessage(0x14,me,(void*)GetCurrentThreadId());
    // send message to self in order for my parent to know how to identify me via threadID
    HHOOK mousehook = SetWindowsHookEx(WH_MOUSE_LL, (LRESULT (*)(int,WPARAM,LPARAM))arg,NULL, 0); // I am line 78
    if (mousehook == NULL) printf("Mousehook error %lu\n",GetLastError());
    //...
}

这没有任何意义，因为我正在转换为它期望接收的确切类型，没有任何限定符或任何不同的东西。这里可能发生了什么？

Answer 1

编译器忽略了错误消息中的调用约定——SetWindowsHookEx 想要一个 LRESULT (__stdcall *)(int,WPARAM,LPARAM)，但您传递一个 LRESULT (__cdecl *)(int,WPARAM,LPARAM)。