dlopen() returns undefined symbol for library w/ RTLD_LAZY

["Steve Lawler" <mirrorsh at atlantech dot net>]

I am using gcc-2.95.2 and glibc-2.2 (sadly, I am using RH7.0's glibc-2.2) w/ Linux 2.4.2.  Now perhaps I don't know how dlopen() is supposed to work, but....

 

If I try to dlopen() a shared library with RTLD_LAZY, and the library in question references an external symbol that is not defined in a system library (like libc or something), dlopen() fails and dlerror will print: "X.so: undefined symbol: FOO".

 

For example:

 

lib1.c:

#include <stdio.h>

 

extern int x(void);

 

void lib1_func(void) { printf("x = %d\n", x); }

-------------------

 

test.c:

#include <stdio.h>

 

int x(void) { return 99; }

 

int main(void) {

    void *h;

    h = dlopen("./lib1.so", RTLD_LAZY);

    if (!h) { printf("%s\n", dlerror()); }

    if (h) dlclose(h);

    return 0;

}

--------------------

 

$ cc -c lib1.c

$ cc -c test.c

$ ld -shared lib1.o -o lib1.so

$ cc test.o -o test -ldl

$ ./test

./lib1.so: undefined symbol: x

 

 

I thought that RTLD_LAZY forced symbols to be evaluated as they are loaded from the shared object; thus dlopen() would not try to load all of ./lib1.so's symbols immediately upon opening; that would be deferred until, say, I tried to load lib1_func with dlsym(), at which point it would try to resolve x() (and, I would hope, it would be resolved to the 'x' found in test.o but... ?) 

 

Also I am wondering why I don't get a message like "./lib1.so: undefined symbol: printf"