Is my casting wrong?

Question

void xGetFunctionAddress(void* FunctionDefinition, std::string FunctionName)
{
    *static_cast<FARPROC*>(FunctionDefinition) = xProcAddress(Module, FunctionName.c_str());
}

In the above code, I'm trying to get rid of that FARPROC* to make it cross-platform. However, if I cast to long long int (*)(), it gives me the error that it cannot statically cast to that. So when I typedef it, it works:

Ex:

//This works:
void xGetFunctionAddress(void* FunctionDefinition, std::string FunctionName)
{
    typedef __stdcall long long int (*Ptr)();
    *static_cast<Ptr*>(FunctionDefinition) = GetProcAddress(Module, FunctionName.c_str());
}

//This doesn't:
void xGetFunctionAddress(void* FunctionDefinition, std::string FunctionName)
{
    *static_cast<long long int(*)()>(FunctionDefinition) = GetProcAddress(Module, FunctionName.c_str());
}

What am I doing wrong in the second example? :S

It returns FARPROC's signature. Aka typedef __int64 (__stdcall *FARPROC)(); — Brandon, Jun 02 '13 at 01:31

score 3 · Accepted Answer · answered Jun 02 '13 at 01:23

3

Your are casting the void pointer to a function pointer and then dereferencing it. This evaluates to an assignment to a function instead of a function pointer. The following should take of the problem

*static_cast<long long int(__stdcall **)()>(FunctionDefinition) = GetProcAddress(Module, FunctionName.c_str());
                                     ^^

Notice the additional pointer level next to __stdcall.

answered Jun 02 '13 at 01:23

Captain Obvlious

19,754
5
44
74

Wow.. That Magic! I never knew that was what was happening. So if I remove the dereference it would have worked? – Brandon Jun 02 '13 at 01:29
1

No, because it would then evaluated to an rvalue. – Captain Obvlious Jun 02 '13 at 01:30

score 1 · Answer 2 · edited May 23 '17 at 10:25

1

It would be useful to see the specific error message, but it looks like you might be missing the __stdcall dcl-specifier in your static_cast. Does it work if you add that?

Edit:

Looking further, it appears this may not be supported. Please see this answer: https://stackoverflow.com/a/1096349/279130 which seems to address the same question.

edited May 23 '17 at 10:25

Community

1
1

answered Jun 02 '13 at 01:14

jwismar

12,164
3
32
44

No I tried that too. error: invalid static_cast from type 'void*' to type 'long long int (*)() with and without the __stdcall Changing it to the typedef gives no problems at all.. – Brandon Jun 02 '13 at 01:17
OK. Did some additional research. Modifying answer above. – jwismar Jun 02 '13 at 01:21

score 1 · Answer 3 · edited May 23 '17 at 12:18

1

What is GetProcAddress() defined to return?

If it's a void *, you can't portably cast that to a function pointer. See https://stackoverflow.com/a/1096349/37386

edited May 23 '17 at 12:18

Community

1
1

answered Jun 02 '13 at 01:24

user9876

10,954
6
44
66

FARPROC that is something like void(*)(void) – Balog Pal Jun 02 '13 at 01:45

Is my casting wrong?

3 Answers3