c - Precedence of dereference and postfix

Question

When I read the TCPL by K&R, I just couldn't understand two expressions:

*p++ = val;  /*push val onto stack */

Here is my idea:

• dereference and postfix has the same precedence, and associativity is right to left,so

  *p++ = val maybe the same with *(p++) = val, because the pointer usually is the next position to the top , so in this code, p increase 1 first because of the parenthesis, so the p is the two units above the current top ,but not the one unit above the current top ,where the val should be!!! Thx

Answer 1

The prefix increment/decrement and dereference operators are equal precedence, but the postfix operator is higher, so *p++ is the same as *(p++), which is like writing *p = val; p++;

If you wrote (*p)++ = val, it wouldn't compile, as you'd be trying to assign a value to a number.