[SOLVED] Address of function is not actual code address

Address of function is not actual code address

Debugging some code in Visual Studio 2008 (C++), I noticed that the address in my function pointer variable is not the actual address of the function itself. This is an extern "C" function.

int main() {
   void (*printaddr)(const char *) = &print; // debug shows printaddr == 0x013C1429

}

Address: 0x013C4F10
void print() {
  ...
}

The disassembly of taking the function address is:

   void (*printaddr)(const char *) = &print;
013C7465 C7 45 BC 29 14 3C 01 mov         dword ptr [printaddr],offset print (13C1429h)

EDIT: I viewed the code at address 013C4F10 and the compiler is apparently inserting a "jmp" instruction at that address.

013C4F10 E9 C7 3F 00 00   jmp         print (013C1429h)

There is actually a whole jump table of every method in the .exe.

Can someone expound on why it does this? Is it a debugging "feature" ?

Solution

That is caused by 'Incremental Linking'. If you disable that in your compiler/linker settings the jumps will go away.

http://msdn.microsoft.com/en-us/library/4khtbfyf(VS.80).aspx