Question

I am trying to compile a toolkit on mac. It has a reference to memalign function of malloc.h, but the only close function I could find for mac is posix_memalign. So I am trying to wrap posix_memalign to look like memalign.

I am a bit confused about how to do this (because of the void* and void** pointers):

The signature for posix_memalign is

int posix_memalign(void **memptr, size_t alignment, size_t size); 

and the signature for memalign is:

void *memalign(size_t blocksize, size_t bytes);

Any pointers much appreciated. ( Lame pun accidental! 🙂

thanks

Answer 1

Something like:

void *memalign(size_t blocksize, size_t bytes) {
  void *result=0;
  posix_memalign(&result, blocksize, bytes);
  return result;
}

The &result will get you a void** to call posix_memalign with and then you can return the result as memalign did.

One point to note: this doesn’t quite match the behaviour – memalign returns errors via errno, but posix_memalign returns them as an int and doesn’t touch errno. You should see to it that errors are handled appropriately somehow still.