Function stbi__addsizes_valid

lite/example/cpp_example/mge/cv/stb_image.h:1027–1035

return 1 if the sum is valid, 0 on overflow. negative terms are considered invalid.

// return 1 if the sum is valid, 0 on overflow.
// negative terms are considered invalid.
static int stbi__addsizes_valid(int a, int b) {
    if (b < 0)
        return 0;
    // now 0 <= b <= INT_MAX, hence also
    // 0 <= INT_MAX - b <= INTMAX.
    // And "a + b <= INT_MAX" (which might overflow) is the
    // same as a <= INT_MAX - b (no overflow)
    return a <= INT_MAX - b;
}

// returns 1 if the product is valid, 0 on overflow.
// negative factors are considered invalid.