指针和数组的删除行为不同

Question

I stumbled on this problem while tinkering with old school arrays. An interesting one though:

a[] = {1,2,3,4,5};
a[][] = {{1,2,3,4}, {4,5,6,7}, {8,9,10,11}, {12,13,14,15}}

Consider 2 scenarios:

1.)

void func(int *a) { //passing a 1D array
   a[1] = 100; //modified an element here
   delete a;  //This would have no effect on the array outside this function. 
}

2.)

void func(int (*a)[4]) { //passing a 2D array
   a[1][2] = 100; //modified an element here of 2D array
   delete a;  //Would have an effect on the outside. Would delete a[0][0]'s memory outside.
} 

Question is why? In 1.) pointer shall point to an array variable memory hence, the delete signature won't clear the memory a[0]?

In 2.) the signature of parameter and passed variable match exactly hence the delete would indeed delete the memory held by local variable?

Any pointers here?

Answer 1

You're invoking undefined behavior on multiple levels. Calling delete on an array rather than delete[] ...and calling any form of delete on an object not allocated with new .

Your program can do anything it wants.