dlsym() returns 'symbol not found'

Asked Nov 08 '13 at 15:23

Active Nov 08 '13 at 16:54

Viewed 4,292 times

I'm using OS X 10.7 (Lion), XCode 4.6.3 and libstdc++ as the C++ Standard Library.

I have this code in my main project:

shared.cpp:

extern "C" int sharedFun()
{
    return 5;
}

And this in my side project, that needs to dynamically load the main one:

loader.cpp:

#include <dlfcn.h>

int main(int argc, const char * argv[])
{
    void* mainApp = dlopen("mainApp.dylib", RTLD_LAZY);

    char* error;
    dlsym(mainApp, "sharedFun");

    if ((error = dlerror()) != nullptr)
    {
         ....
    }
}

nm output:

nm -gU mainApp.dylib | grep sharedFun
002a3a10 - 01 0000   FUN _sharedFun
002a3a10 T _sharedFun

dlopen loads the library just fine, but dlsym returns "symbol not found". Any ideas?

Thanks.

edited Nov 08 '13 at 16:54

asked Nov 08 '13 at 15:23

Tsury

1

Why aren't you assigning the return value of `dlsym()` to a variable? – trojanfoe Nov 08 '13 at 15:26
I am (in my original code), but it is irrelevant here. – Tsury Nov 08 '13 at 15:41
2

Sure, but you probably need to assure viewers of your question that you are checking for error by checking for a null return from `dlsym()` rather than relying on `dlerror()` alone. If nothing else, it avoids questions like mine. – trojanfoe Nov 08 '13 at 15:44
1

Are you sure that `dlopen` is successfully opening your library? – Sean Nov 08 '13 at 15:49
1

Do you have a typo in your real code as well? – molbdnilo Nov 08 '13 at 15:52
the mainApp handle is not null after the dlopen line, and when checking dlerror right after dlopen, it returns null. – Tsury Nov 08 '13 at 15:52
molbdnilo, what typo? (Obviously it compiles and runs just fine) – Tsury Nov 08 '13 at 15:53
Is that because of the *lazy flag*? – trojanfoe Nov 08 '13 at 16:01
Scratch that *again*. dlopen is working. I also tried the other NOW | GLOBAL variations, still no go. – Tsury Nov 08 '13 at 16:05
shared.cpp calls it `sharedFunc`. Is this intentional? – Anya Shenanigans Nov 08 '13 at 16:46
It was a typo in the post and not in the code. Fixed. – Tsury Nov 08 '13 at 16:55

dlsym() returns 'symbol not found'

0 Answers0