C++: delete vs. free and performance

Question

1. Consider:

   char *p=NULL;
   free(p) // or
   delete p;
   

   What will happen if I use free and delete on p?

Answer 1

Question one: nothing will happen.

From the current draft of ISO/IEC 14882 (or: C++):

20.8.15 C Library [c.malloc]

The contents [of , that is: where free lives,] are the same as the Standard C library [(see intro.refs for that)] header , with the following changes: [nothing that effects this answer].

So, from ISO/IEC 9899:1999 (or: C):

7.20.3.2 The free function

If [the] ptr [parameter] is a null pointer, no action occurs.

From the C++ standard again, for information about delete this time:

3.7.4.2 Deallocation functions [basic.stc.dynamic.deallocation]

The value of the first argument supplied to a deallocation function may be a null pointer value; if so, and if the deallocation function is one supplied in the standard library, the call has no effect.

See also:

• What is the difference between new/delete and malloc/free?
• What happens when you try to free() already freed memory in c?