CODEWITHSUNDEEP
clinuxlinkersymbols
akris
akris

Reputation: 57

Symbols in .lib are not there in .so

I have a library file (.lib) where there are many functions. I am trying to build a shared object out of it. But non of the symbols in library are there in shared object that are in library. However, when I generate executable out of the same library the symbols are visible.

Is some thing wrong with libraries? Do I need to compile libraries in a format suitable for creating shared object?

Upvotes: 0

Views: 726

Answers (1)

Maxim Egorushkin
Maxim Egorushkin

Reputation: 136208

What linkers do is they pull only those .o files from an archive .a that resolve an unresolved symbol.

When you link a shared library and pass only .a files to the linker, there are no unresolved symbols, hence no object files from .a get pulled into the shared library.

To link a shared library the object files must be compiled as position independent code (-fPIC, .o files for .a are normally built without this option) and then linked into a shared library. No .a files are necessary for that.

Another option is when linking .a files is to explicitly undefine the symbols that are present in .a using -Wl,--undefined=<symbol> linker option. But this does not scale well because it requires mentioning at least one symbol from each .o comprising .a (assuming the linker pulls in an entire .o, rather than just one symbol from it).

Upvotes: 3

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