What should I do if two libraries provide a functi

Question

What should I do if I have two libraries that provide functions with equivalent names?

Answer 1

Swear? As far as I am aware, there isn't much you can do if you have two libraries that expose link points with the same name and you need to link against both.

Answer 2

It is possible to rename symbols in an object file using objcopy --redefine-sym old=new file (see man objcopy).

Then just call the functions using their new names and link with the new object file.

Answer 3

Under Windows, you could use LoadLibrary() to load one of those libraries into memory and then use GetProcAddress() to get the address of each function you need to call and call the functions through a function pointer.

e.g.

HMODULE lib = LoadLibrary("foo.dll");
void *p = GetProcAddress(lib, "bar");
// cast p to the approriate function pointer type (fp) and call it
(*fp)(arg1, arg2...);
FreeLibrary(lib);

would get the address of a function named bar in foo.dll and call it.

I know Unix systems support similar functionality, but I can't think of their names.

Answer 4

I've never used dlsym, dlopen, dlerror, dlclose, dlvsym, etc., but I'm looking at the man page, and it gives an example of opening libm.so and extracting the cos function. Does dlopen go through the process of looking for collisions? If it doesn't, the OP could just load both libraries manually and assign new names to all the functions his libraries provide.

Answer 5

You should write a wrapper library around one of them. Your wrapper library should expose symbols with unique names, and not expose the symbols of the non-unique names.

Your other option is to rename the function name in the header file, and rename the symbol in the library object archive.

Either way, to use both, it's gonna be a hack job.

Answer 6

You should not use them together. If I remember correctly, the linker issues an error in such a case.

I didn't try, but a solution may be with dlopen(), dlsym() and dlclose() which allow you to programmatically handle dynamic libraries. If you don't need the two functions at the same time, you could open the first library, use the first function and close the first library before using the second library/function.