Problems with linking of shared libraries in AIX

    Normally, in Solaris, Linux and other common platforms, shared libraries are represented with .so/.sl suffix. Static libraries are represented with .a suffix in filenames. But in AIX, static libraries have .a suffix and shared libraries can have either .so or .a suffix.

when we try to compile a c file which uses shared library with .so suffix, it wont succeed by default. It gives a compilation error. Additionally we have to pass “-Wl,-brtl” flag to the compiler. “-Wl” is to say that it is a flag to the linker, so “-brtl” is internally passed to the linker [ld]. “-brtl” says that it should consider files with .so suffix also as shared libraries. There is no need to pass this flag when your shared library contains .a suffix. This type of linking is loadtime linking.

When we want to access a shared library at runtime using dlopen & dlsym calls, it is called runtime linking. In this case, we wont get any compilation errors. If the shared library contains .a suffix, we wont get any errors at runtime also. But if the shared library contains .so suffix, we get segmentation fault at runtime. Confusing thing is, it succesfully executes dlopen call, but at the time of dlsym, it exits with segmentation fault. If we give “-Wl-brtl” flag to compiler at compilation time, runtime linking goes fine.


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