Are there general guidelines for solving undefined reference/unresolved symbol issues?

Question

I\'m having several \"undefined reference\" (during linkage) and \"unresolved symbol\" (during runtime after dlopen) issues where I work. It is quite a large makefile system

Answer 1

Setting up a build system where X depends on Y which depends on Z helps. It's when you get into circles (Z depends on X) that things get ugly.

Oftentimes it's the order libraries are linked ("-lZ -lY -lX" vs "-lX -lY -lZ") that causes grief. More rarely, you have the same library-name in multiple places on your search path, or your linking against outdated versions that have not yet been recompiled.

"nm --demangle" can let you see where things are defined/used.

"ldd" can be used to see what dynamic libraries you depend on.

The gcc/g++ flag -print-file-name=LIBRARY can help track down exactly which library is being used.

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Afterthought: (Since you ask about rules/guidelines.)

It is possible to set up a makefile system such that:

• If module=D depends on modules A,B,&C.
• Then trying to make module=D would first make modules A,B,&C.
• And, more importantly, module=D would automatically determine its libraries (-lA,etc), library paths (-LA), and include paths (-IA) from the makefiles for modules A,B,&C.

That can get a little hairy to set up. Last time I did it, I favored merely caching the information rather than forking an excessive number of make subprocesses. Coupled with makefile-importing and a little perl script to remove duplicates. Kludgey, I know. (Powers that be didn't want to spend time on infrastructure.) But it can be done.

Then again, I was using GNU-make, which has a few extensions.