Pointer operations and operator precedence in C

Question

Background

Just had a chat with a C guy today and we disagreed on the following:

int intgA[2] = { 1, 2 };
int intgB[2] = { 3, 5 };

int *intAPtr = intg         


        

Answer 1

The statement

*intAPtr++ = *intBPtr++;

is parsed as

*(intAPtr++) = *(intBPtr++);

and breaks down as follows:

• The value currently pointed to by intBPtr (3) is assigned to the location pointed to by intAPtr (intgA[0]);
• The pointers intAPtr and intBPtr are incremented.

The exact order in which these things happen is unspecified; you cannot rely on intBPtr being incremented after intAPtr or vice-versa, nor can you rely on the assignment occuring before the increments, etc.

So by the time this is all done, intgA[0] == 3 and intAPtr == &intgA[1] and intBPtr == &intgB[1].

The expression a++ evaluates to the value of a before the increment.