4

I found that when I compile my C/C++ programs with VS2010 (I haven't checked other compilers) in Debug mode, when I look at the disassembly, all function calls, whether to library functions, my own functions, class member functions etc. all have a 2-step call. The actual function call is translated to a call instruction to an address, A. When I go to address A, I see it is some kind of large list of jmp instructions, each to a different function. A (small) part of it might look like this

fooFunc:
08CB1776  jmp         fooFunc (8D11F60h) 
barFunc:
08CB177B  jmp         barFunc (8D25240h) 
std::allocator<unsigned int>::max_size:
08CB1780  jmp         std::allocator<unsigned int>::max_size (8CE3D00h) 
std::_Copy_backward_opt<int *,int *>:
08CB1785  jmp         std::_Copy_backward_opt<int *,int *> (8D325D0h) 
std::_Checked_base<int *>:
08CB178A  jmp         std::_Checked_base<int *> (8D32360h) 
@ILT+1950(_foobarFunc):
08CB17A3  jmp         foobarFunc (8F31450h) 
@ILT+1955(_anotherFunc):
08CB17A8  jmp         anotherFunc (8E4BD20h) 
std::vector<unsigned short,std::allocator<unsigned short> >::capacity:
08CB17B2  jmp         std::vector<unsigned short,std::allocator<unsigned short> >::capacity (8D8AAF0h) 
yetAnother:
08CB17B7  jmp         yetAnother (8D18630h) 
@ILT+1975(_f):
08CB17BC  jmp         f (8E4FC50h) 
std::_Debug_range<char *>:
08CB17C6  jmp         std::_Debug_range<char *> (8D32480h) 
std::_Vector_const_iterator<MyClass *,std::allocator<MyClass *> >::operator+=:
08CB17CB  jmp         std::_Vector_const_iterator<MyClass *,std::allocator<MyClass *> >::operator+= (8D64C80h)

These jmp instructions in turn go to the actual function bodies. This is only when compiling in Debug mode. In Release, the function calls are compiled into direct calls to the function body.

What is the point of this indirect function calling?

Daniel A. White
  • 187,200
  • 47
  • 362
  • 445
Baruch
  • 20,590
  • 28
  • 126
  • 201
  • 1
    Perhaps some insight in this http://stackoverflow.com/questions/10859188/in-visual-studio-debugmode-compiled-executable-jmp-to-function-body-instead-of although I'm not sure it's exactly a duplicate. – jcoder Dec 02 '13 at 13:35

1 Answers1

0

Here's the answer by @RaptorFactor:

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

egur
  • 7,830
  • 2
  • 27
  • 47