Arithmetic operation on int32 and int64 with parentheses

Question

given this operation:

int64_t a_int64, b_int64 = WHATEVER1;
int32_t c_int32 = WHATEVER2;

a_int64 = b_int64 - (c_int32 * 1000000);

Is c_int32 promoted to int64_t before the multiply? I know all integers are promoted to at least 'int' size before any arithmetic operations, and to the size of the larger operand for binary operators if this is of greater rank than an int. But are operations inside parentheses' are handled separately from the (second) operation, the substraction?

Answer 1

But are operations inside parentheses' are handled separately from the (second) operation, the substraction?

Yes; the promotions involved in evaluating c_int32 * 1000000 do not depend in any way on the context. Any necessary conversions due to that context happen on the result, afterward.

That said, c_int32 * 1000000 is only well-defined in cases where it doesn't overflow; and in such cases, it doesn't matter whether the 64-bit promotion happens before or after the multiplication. So a compiler could legitimately do it either way (e.g., if it sees some optimization opportunity).