dlsym() problem

subham · 10-22-2010, 12:41 PM

dlopen() is working correctly but dlsym() says cannot find symbol.

Here are my C (not C++) codes:
------
f1.c
------
#include<dlfcn.h>

int main()
{
char *str="name";
void *handle=dlopen("libsharedtest.so",RTLD_LAZY);
void (*p)(char *);
p = (void (*)(char *))dlsym(handle,"printer");
char* lError = dlerror();
if (lError)
{

printf("Error: %s\n", lError);
}
(*p)(str);
dlclose(handle);
return 0;
}

-----
f2.c
-----

#include<stdio.h>

void printer(char *str)
{
printf("%s",str);
}

codewad · 10-22-2010, 05:59 PM

If you're using gcc, there's a good chance that it's running your symbols through it's C++ name mangling stuff, even though you're coding in C.

The way I know of to fix this is to use extern "C" in your dynamic lib code, something like this:

Code:

#include<stdio.h>

extern "C" {

  void printer(char *str)
  {
    printf("%s",str);
  }

}

This will tell the compiler not to mangle the symbol names. There are also a couple other ways to use extern "C", I think. This is just the only way I remember off the top of my head.