dlsym-like functionality for non-dynamically-loaded code?

Question

I know how to use dlsym() to find symbols keyed by a string - when these symbols are exported by a shared library which I've dlopen()ed. But - what about other code? Just object code I've linked statically. Is it possible to somehow lookup symbols?

Notes:

• If it helps, make any reasonable assumptions about the compilation and linking process (e.g. which compiler, presence of debug info, PIC code etc.)
• I'm interested more in a non-OS-specific solution, but if it matters: Linux.
• Solutions involving pre-registration of functions are not relevant. Or rather, maybe they are, but I would rather avoid that.

Answer 1

You can indeed just use dlsym() for that purpose.. You just have to export all symbols to the dynamic symbol table. Link the binary with gcc -rdynamic for that.

Example:

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

void foo (void) {
    puts("foo");
}

int main (void) {
    void (*foo)(void) = dlsym(NULL, "foo");
    foo();
    return 0;
}

Compile with: gcc -rdynamic -O2 dl.c -o dl -ldl

$ ./dl
foo
$