Very Computer

hi, I've been puzzled by the mention of an RTLD_GLOBAL flag in the dlopen
man page; theoretically, you dlopen() a shared object with RTLD_GLOBAL in
the flags, and the object's symbols are then visible to anything else that
gets dlopened later. However, when I tried this I discovered that there Is No
RTLD_GLOBAL defined in the header files!

I really, really, REALLY need to make loaded modules visible to each other.
Has anyone done so successfully?

James

The key is probably to get a newer ld.so ... I believe anything
at 1.7.10 or above will do it; you will want 1.7.11 or better to
fix a bug with dlsym in 1.7.10.  Here is a test set; I just checked
it here.

all: mod1.so mod2.so driver

mod1.so: mod1.c
        gcc -fPIC -shared mod1.c -o mod1.so

mod2.so: mod2.c
        gcc -fPIC -shared mod2.c -o mod2.so

driver: driver.c
        gcc driver.c -o driver -ldl

clean:
        rm -f mod1.so mod2.so driver

int foo_var = 3;

#include <stdio.h>

extern int foo_var;
int foo_print() {
        printf("%d\n", foo_var);

Quote:}

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

int main(int argc, char **argv) {
    void *handle1, *handle2;
    void (*print)();
    const char *error;

          printf("mod1.so: ");                              
    handle1 = dlopen ("./mod1.so", RTLD_LAZY | RTLD_GLOBAL);
    if (!handle1) {
        fputs (dlerror(), stderr);
        exit(1);
    }
                printf("loaded.\n");

          printf("mod2.so: ");
    handle2 = dlopen ("./mod2.so", RTLD_LAZY | RTLD_GLOBAL);
    if (!handle2) {
        fputs (dlerror(), stderr);
        exit(1);
    }
                printf("loaded.\n");

                print = dlsym(handle2, "foo_print");
    if ((error = dlerror()) != NULL)  {
        fputs(error, stderr);
        exit(1);
    }

    (*print)();
    dlclose(handle1);
    dlclose(handle2);

Quote:}

enjoy =)

driver.c is prety much from man dlopen, btw...

good luck!
--randy

: hi, I've been puzzled by the mention of an RTLD_GLOBAL flag in the dlopen
: man page; theoretically, you dlopen() a shared object with RTLD_GLOBAL in
: the flags, and the object's symbols are then visible to anything else that
: gets dlopened later. However, when I tried this I discovered that there Is No
: RTLD_GLOBAL defined in the header files!

: I really, really, REALLY need to make loaded modules visible to each other.
: Has anyone done so successfully?

: James