dlclose() doesn't work with factory function & complex static in function?

Question

I\'m making a simple plugin framework in which I\'d like to be able to dlopen() a shared library (i.e. plugin), inspect and use whatever factory functions is provides and ev

Answer 1

What's happening is that there is a STB_GNU_UNIQUE symbol in libempty.so:

readelf -Ws libempty.so | grep _ZGVZN3Foo4initEvE2ns
 91: 0000000000203e80     8 OBJECT  UNIQUE DEFAULT   25 _ZGVZN3Foo4initEvE2ns
 77: 0000000000203e80     8 OBJECT  UNIQUE DEFAULT   25 _ZGVZN3Foo4initEvE2ns

The problem is that STB_GNU_UNIQUE symbols work quite un-intuitively, and persist across dlopen/dlclose calls.

The use of that symbol forces glibc to mark your library as non-unloadable here.

There are other surprises with GNU_UNIQUE symbols as well. If you use sufficiently recent gold linker, you can disable the GNU_UNIQUE with --no-gnu-unique flag.