Question

I am trying to understand a C code from another programmer. Sometimes I get segmentation faults and I think it could be due to stack overflow. I wonder whether in Visual Studio (or another way) is it possible to estimate in an easy way, given a call to a function, the size it will need on the stack when creating variables.

Thanks

Answer 1

The size of a frame on the stack is roughly the sum of the sizes of the parameters passed in plus the sum of the sizes of the local variables. There is also a little extra for the return address, base pointer, and perhaps some guard cookies for checking stack overruns.

Example:

int foo(int x, int y, char *string) {
  int array[10000];
  // ...
}

Integers in VC++ are 4 bytes each. A pointer is 4 bytes in a 32-bit executable, or 8 bytes in a 64-bit executable. So the parameters add up to 4+4+8. The local array is 40,000 bytes. This function consumes roughly 40 KB of stack. You could add up a lot of those before you overrun the stack.

An actual stack overflow in a Windows program generally only happens with runaway recursion. The default stack size is pretty large (1 MB). You can get stack corruption by overrunning a buffer that’s on the stack.

Chances are your crash has to do with accessing an array beyond its bounds or accessing through a pointer that isn’t pointing to valid memory (e.g., a NULL pointer).