Why signed integer overflow sucks

// Compile on a recent version of clang and run it:
// clang++ -std=c++11 -O3 -Wall -fsanitize=undefined stdint16.cpp -o stdint16
//
// You'll get a nice error:
// main.cpp:20:55: runtime error: signed integer overflow: 65535 * 65535 cannot be represented in type 'int'
//
// What's just awesome about this is that avoiding this problem portably (i.e.
// without depending upon a particular size of "int") requires a maze of "if"
// or "#if" statements or doing your multiplications using uintmax_t.  Great
// solution, huh? >.<
//

#include <cinttypes>
#include <cstdint>
#include <cstdio>

int main()
{
     std::uint8_t a =  UINT8_C(              0xFF); a *= a; // OK
    std::uint16_t b = UINT16_C(            0xFFFF); b *= b; // undefined!
    std::uint32_t c = UINT32_C(        0xFFFFFFFF); c *= c; // OK
    std::uint64_t d = UINT64_C(0xFFFFFFFFFFFFFFFF); d *= d; // OK

    std::printf("%02" PRIX8 " %04" PRIX16 " %08" PRIX32 " %016" PRIX64 "\n", a, b, c, d);

    return 0;
}