ptrdiff_t

Uses of the ptrdiff_t Data Type

C and C++ define a special type for pointer arithmetic, namely ptrdiff_t, which is a typedef of a platform-specific signed integral type. You can use a variable of type ptrdiff_t to store the result of subtracting and adding pointers. For example:

  #include <stdlib.h> int main() { int buff[4]; ptrdiff_t diff = (&buff[3]) - buff; // diff = 3 diff = buff -(&buff[3]); // -3 } 

What are the advantages of using ptrdiff_t? First, the name ptrdiff_t is self-documenting and helps the reader understand that the variable is used in pointer arithmetic exclusively. Secondly, ptrdiff_t is portable: its underlying type may vary across platforms, but you don't need to make changes in the code when porting it.