dynamically loading static library?

Question

Can a static libary *.a in Linux be dynamically loaded at runtime?
I've read here that

...both static and shared libraries can be used as dynamically loaded libraries.

How to dynamically load static library?

Answer 1

A static library is more or less just a collection of object files. If you want to use a static library in a program, you have to link the executable with it. The executable will then contain the static library (or the parts that you used).

If you want to load a static library at runtime using dlopen, you will have to first create a dynamic library libfoo.so containing it.

Answer 2

Opening a .a file using dlopen does not work (tested on Ubuntu 10.04). With the following example program:

#include <dlfcn.h>
#include <stdio.h>

int main()
{
  void *lib_handle = dlopen("/usr/lib/libz.a",RTLD_LAZY);
  printf("dlopen error=%s\n",dlerror());

  printf("lib_handle=%p\n",lib_handle);
}

I get:

dlopen error=/usr/lib/libz.a: invalid ELF header
lib_handle=(nil)

while when using /usr/lib/libz.so instead, I get:

dlopen error=(null)
lib_handle=0x19d6030

so the same code works for a shared object.