I'm trying to link a C++ binary, but I get undefined symbol errors. My binary shouldn't need those symbols, and I'd like to understand the dependency chain causing the linker (GNU ld or GNU gold) think that they are needed. There is libfoo.a containing hundreds of .o files. My program is calling function in libfoo.a. I'd like to get a dependency graph containing all .o files in libfoo.a which the linker thinks are needed to link my program.

I need it because I suspect that there is a mistake somewhere in libfoo.a, calling functions which are not really needed. I can modify the source code of libfoo.a (and thus remove the unneeded calls), and for that I need to understand where the unneeded calls are. The dependency graph could help me find it.

Please note that there is no resulting executable, because of the undefined symbols.

Please note that my ultimate goal is not to build this particular binary, but to make sure that unneeded functions are not called in libfoo.a.

I've looked at man ld, but I couldn't find any command-line flag that could give me more verbose output.

Example error from the linker:

libfoo++.a(foo1.o):foo1.cc:function foo1f: error: undefined reference to 'bar'

How do I figure out what caused foo1.o to be linked to the executable? (It's OK for me that bar is undefined, because I don't need it. My problem is that foo1.o is needed, but it shouldn't be, and I'd like to remove the call which caused foo1.o to be linked in.)