Thread: Shared Library Not Executing Function

I think it's good of you to post a link to your other post, rather than replicate the post here - but it's still a kind of cross posting, which leads to this:
1. This question probably should be in the Linux section.
2. What makes you think this forum is better at answering a Linux question here than on a board that is SPECIFICALLY for Linux?

--
Mats

Well, because this is more of a programming issue than a Linux issue (or at least I think it is), and while that is a Linux forum with a SECTION for programming, this is programming forum with a SECTION for Linux. I figure you guys might know better than they would, seeing as (I would assume) all of the user base is made up of programmers, whereas there only a certain percentage is.

Shane

1. Moved to correct forum.

> but it's still a kind of cross posting
2. It's the more acceptable kind, since Osiris990 has actually waited for several days without reply before trying the next forum on the list. It's the ones who broadcast in several places at the same time which are the real bane.

3. A 1-function main() calling a 1-function DLL, and showing how you linked the various components.

Code:

$ cat bar.c
#include <stdio.h>
#include <dlfcn.h>

void myfunc ( void (*fn)(void) ) {
  printf("In dl func, calling back\n" );
  fn();
  printf("In dl func, done\n" );
}

$ cat foo.c
#include <stdio.h>
#include <dlfcn.h>

void callback ( void ) {
    printf("In callback\n");
}

int main() {
    void *lib = dlopen("bar.so",RTLD_NOW);
    if ( lib ) {
        void *f1 = dlsym(lib,"myfunc");
        void (*func)(void (*)(void)) = (void(*)(void (*)(void)))f1;
        func(callback);
        dlclose(lib);
    } else {
        printf("&#37;s\n",dlerror() );
    }
    return 0;
}

$ gcc -o bar.so bar.c -shared
$ gcc foo.c
$ ./a.exe
In dl func, calling back
In callback
In dl func, done

Experiment with simple ideas, then try to integrate them into your main application.
Also, experiment with the major ideas you're likely to need in the whole project before trying to actually use them.

Originally Posted by GNU LD Manual

--export-dynamic
When creating a dynamically linked executable, add all symbols to the dynamic symbol table. The
dynamic symbol table is the set of symbols which are visible from dynamic objects at run time.

If you do not use this option, the dynamic symbol table will normally contain only those symbols
which are referenced by some dynamic object mentioned in the link.

If you use dlopen to load a dynamic object which needs to refer back to the symbols defined by
the program, rather than some other dynamic object, then you will probably need to use this
option when linking the program itself.

You can also use the version script to control what symbols should be added to the dynamic symbol
table if the output format supports it. See the description of --version-script in VERSION.

I started with these commands.

Code:

gcc -g -ansi -o circbot circbot.c circbot_irc.c circbot_settings.c -ldl -lpcre
gcc -g -ansi -o modules/test.so test.c -shared -Wl,--just-symbols=circbot

It didn't produce any warnings, but neither did it run (or didn't seem to at any rate, it could just be cygwin). At any rate, perhaps it will provide some clues.

GNU LD certainly seems capable of doing what you ask, it's just a matter of getting the right options. But tiredness (and flu) is slowing me down .

I understand what it is you're trying to do (.exe depends on .so, and .so depends on .exe).