Question

What is the difference between the following pointer expressions

*ptr++

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++*ptr

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(*ptr)++

Answer 1

The first one will is equivalent to *(ptr++) which will will return a temporary pointer with it’s current value and then increment ptr.

The second one will increment the value pointed to by ptr (assuming it is a type with ++ defined) and return the incremented value

The third one will return the current value pointed to by ptr and then increment ptr

Ex.

int a = 0;
int * ptr = &a;
int b = *ptr++;

a = 0, b = 0, but ptr will point to nonsense.

int a = 0;
int * ptr = &a;
int b = ++*ptr;

a = 1, b = 1

int a = 0;
int * ptr = &a;
int b = (*ptr)++;

a = 1, b = 0