I was surprised that gcc did not find an error in the following example.
My understanding is that assignment to a void pointer is ok, but arithmetic
is _not_ ok. I have tried this code on my arm cross compiler gcc v. 4.1.1 and my ubuntu system compiler 4.1.3. Gcc treats the void pointer type as char 

gcc --version
        gcc (GCC) 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)

Example pointer arithmetic on a void pointer that should have caused an error
   #include <stdlib.h>
   int main (int argc, char **argv)
   {
      void *x;
      x = malloc(1025 * sizeof(*x));

      x++;    // i expected an error on this line!

      return 1;
   }