dlopen on new binary with same name returns old handle

Question

I\'m using dlopen to load dynamically generated code. The program calls the compiler on the code and generates a .so file which is then loaded by the program to extend itsel

Answer 1

Most probly dlclose failed to unload the library. This usually happens when it contains GNU_UNIQUE symbols (which tend to sneak in if you link with static libstdc++). This can be verified via

$ readelf -sW --dyn-syms path/to/libxyz.so | grep '\bUNIQUE\b'
...
3808: 0000000000302e78     8 OBJECT  UNIQUE DEFAULT   27 _ZNSt8messagesIcE2idE@@GLIBCXX_3.4

To fix this, you can try one of the following:

• build library with -fvisibility=hidden and __attribute__((visibility("default"))) to hide unique symbols
• build with -Wl,--version-script to achieve the same
• build shlib with toolchain that was configured with --disable-gnu-unique-object (see discussion in GCC list)