Proper use libdl and dynamically linked libraries

Question

I need to dynamically link a library that I have created. I'm not exactly sure what the issue is. It all compiles properly, but I always catch

handle

as the

NULL

pointer:

void *handle;

char *error;

handle = dlopen ("./hw11-lib-michaelSchilling.so", RTLD_LAZY);

//same error comes up with full path as well as './hw11...'

if(!handle){

    error = dlerror();

    printf("%s\n", error);

    printf("Error loading library.\n");

    exit(1);

}

I cant get passed this error and I'm not sure what could possibly be wrong. I'm pretty sure I've compiled everything correctly. Here are the compilation steps I used:

gcc -rdynamic -c hw11-lib-michaelSchilling.c -o hw11-lib-michaelSchilling.so

gcc hw11-michaelSchilling-4.c -ldl -o hw11-michaelSchilling-4

I'm getting an error that reads

./hw11-lib-michaelSchilling.so: only ET_DYN and ET_EXEC can be loaded.

What does this mean?

Thanks.

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Answer 1

When building hw11-lib-michaelSchilling.so, you don't appear to be telling gcc that you want a shared object (the .so in the name isn't enough).

With the -c it's producing an object file (not a shared object) and calling it michaelSchilling.so. The linker doesn't even get invoked.

Remove the -c from the gcc command line and add -shared:

gcc -shared -rdynamic hw11-lib-michaelSchilling.c -o hw11-lib-michaelSchilling.so

Proper use libdl and dynamically linked libraries

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