Question

I’m having some trouble with c code from a library that I use with Android NDK.

It works on the emulator, but not on a real device. It gives me a “libc – Fatal signal 11” (SIGSEGV)

I have traced the problem to a piece of code in the library, but I’m having trouble understanding what the second line does.

Here is the code:

int lookup_mpz(mpz_t z, const char *(*tab)(const char *), const char *key) {
  const char *data= tab(key); //--> Causes SEGV
  if (!data) {
    pbc_error("missing param: `%s'", key);
    return 1;
  }
  mpz_set_str(z, tab(key), 0);
  return 0;
}

Answer 1

The second line is invoking a function, via a function pointer named tab. The function has the signature:

const char* f(const char*);

Suggest checking that key and tab() are not NULL prior to calling tab().