Cheat Engine

[iPromise]

How would we determine the size of a function?

For example, the size of LoadLibraryA or your own usermode function.

[Dark Byte]

Follow all direct jumps (conditional or normal)
And from the largest jumplocation go down till you find a ret

And take care of situations that are just stupid. E.g,: The windows vista+ function stubs for kernelbase.dll functions

[Slugsnack]

not sure if this applies to portable executables but with elf files, you can parse the symbol table (through the libelf interface) to enumerate functions and find their sizes. i suspect that something similar would be available for PE files through winapi