It's not dereferencing NULL that causes the segfault, its the actual reading or writing of the memory at the invalid address. So, ignoring undefined behavior e

It's not dereferencing NULL that causes the segfault, its the actual reading or writing of the memory at the invalid address. So, ignoring undefined behavior etc, "* ptr;" doesn't actually generate a load or store since its not really doing anything, but "x = * ptr;" or "* ptr = x;" would. You can also see similar behavior when calling a non-virtual member function on a NULL pointer, the crash doesn't occur until the function actually tries to access some data on "this". This is all with the caveat that the actual behavior depends on the system and compiler as many others have pointed out.