Are arguments of the called function part of its stack frame in Intel x86?

Question

Hi everyone and sorry for the silly question. Let's say that "main" calls an "add" function (pseudocode):

main { add(5,10) }

The stack would be something similar:

...main...
|  10   |
|  05   |
|  RET  |
|  EBP  |
...add...

The stack frame of "add" starts from EBP or include also 10, 5 (args) and RET? In a CDECL calling convention the caller (main) is in charge of cleaning the stack after the "add" function returns. I suppose clean means "remove" (by increasing esp) the arguments from the stack, not the local vars of the "add" function, right?

Thanks a lot

Answer 1

The short answer is sometimes. Depending on the calling convention and the compiler, some arguments may be stored in registers rather than on the stack. See this wikipedia article: https://en.wikipedia.org/wiki/X86_calling_conventions#Microsoft_x64_calling_convention

To be a little more clear, if the caller pushes an argument on the stack, the caller is typically responsible for cleaning it up. According to the C specification, a function does not know how many arguments are being passed in to the function (consider functions like printf() and friends) The code that knows how many arguments are actually on the stack and how to deal with them is the calling function. All this is convention, however. C makes very few requirements for how this all actually ties together on any given physical machine.

In practical code, you will usually see sub ESP, in the calling function.