Assertion fails after using memcpy()

I have the following code, where the assertion fails. Can anyone explain me why?

double *E = (double *) malloc(sizeof(double) * voxelSpaceSize);
double *E_new = (double *) malloc(sizeof(double) * voxelSpaceSize);

// ...some manipulations inside E and E_new, the memory loc开发者_Python百科ations do not change though
...

memcpy(E, E_new, sizeof(double) * voxelSpaceSize);        

for (int i=0; i<voxelSpaceSize; i++) {
  assert(E[i] == E_new[i]);
}

By definition, the special floating-point value NaN is not equal to itself: NaN == NaN returns false. So now I'm betting the value at the unequal index is NaN. You may want to print out the value at the index where the value's not equal to itself, rather than using assert.

Assuming you want to copy from E to E_new, your arguments to memcpy are in the wrong order -- the second argument is the source pointer, the first is the destination.