CODEWITHSUNDEEP
c++cdllshared-librariesexe
Mikhail Kipa
Mikhail Kipa

Reputation: 111

Can executable and shared library contain functions with the same name?

What will happen if executable and shared library contain functions with the same name? For example EXE has definition like this:

extern int fund()
{
   return 0;
}

and shared library has same definition:

extern int fund()
{
   return 1;
}

what function will be called from executable and from shared library: 1 - for Windows? 2 - for unix-base?

PS: When I define AfxWinMain in my MFC application, on startup it will be called instead of the AfxWinMain in the MFC DLL. I need some theory why is it so?

Upvotes: 4

Views: 1617

Answers (1)

tofro
tofro

Reputation: 6063

You have answered the question in the heading yourselves already.

Non-shared library dependencies are resolved at link time, not at load time. Once the linker has satisfied that external reference towards a static library, it will stay that way and neither the Windows nor the Unix loader will try to resolve it anymore (the symbol is normally not even "visible" in the binary after the link stage).

When linking against libraries (regardless of static or dynamic), the linker stops searching for a symbol to resolve as soon as it has found a reference that satisfies the requirement and will not look any further in any other (or the same) library for that symbol. That is why you can supply multiple definitions for the same function in libraries (as opposed to object files, those are guaranteed to be searched exhaustively and thus will be checked for duplicate symbols).

Only symbols that need to be resolved at load time are marked as "external shared" and are resolved by the loader at runtime.

I don't see a fundamental difference in this respect between unixoid OSs and Windows.

Upvotes: 4

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