I was trying call a function that complied with the host ELF executable file.

Here is the sample code:

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

// or with some tricks
// void __attribute__((visibility("default")))
void test_func(void)
{
    printf("test_func in %s n",__FILE__);
}

int main()
{
    void *handle = dlopen(0, RTLD_LAZY); // or RTLD_GLOBAL
    printf("dlopen return %pn", handle);

    void (*func)() = dlsym(handle, "test_func");
    printf("dlsym  return %pn", func);

    if (func) (*func)();
    return 0;
}

It failed with output like this:

$ ./a.out
dlopen return 0xe29dfbec1c7bc0d
dlsym  return 0x0

I can read the symbol in the ELF. It hits my head that it must be some way to get the test_func function and call it.

$ readelf -s a.out | grep test_func
    40: 00000000000017c8    36 FUNC    GLOBAL DEFAULT   13 test_func

Is there something I missing? Can it also work in Windows?