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c++windowscode-size

Getting The Size of a C++ Function

I was reading this question because I'm trying to find the size of a function in a C++ program, It is hinted at that there may be a way that is platform specific. My targeted platform is windows

The method I currently have in my head is the following:
1. Obtain a pointer to the function
2. Increment the Pointer (& counter) until I reach the machine code value for ret
3. The counter will be the size of the function?

Edit1: To clarify what I mean by 'size' I mean the number of bytes (machine code) that make up the function.
Edit2: There have been a few comments asking why or what do I plan to do with this. The honest answer is I have no intention, and I can't really see the benefits of knowing a functions length pre-compile time. (although I'm sure there are some)

This seems like a valid method to me, will this work?

Solution

  • No, this will not work:

    1. There is no guarantee that your function only contains a single ret instruction.
    2. Even if it only does contain a single ret, you can't just look at the individual bytes - because the corresponding value could appear as simply a value, rather than an instruction.

    The first problem can possibly be worked around if you restrict your coding style to, say, only have a single point of return in your function, but the other basically requires a disassembler so you can tell the individual instructions apart.