fork(1) download

copy

#include <iostream>
#include <cstdint>
using namespace std;
 
constexpr uint16_t operator "" _int(char const * s, size_t len)
{
    return (len == 2) ? s[0] | (s[1] << 8) : throw "len must be 2!";
}
 
int main() {
    constexpr uint16_t i1 = "AB"_int; // OK
    cout << i1 << endl;
    constexpr uint16_t i2 = "ABC"_int; // error
    cout << i2 << endl;
    return 0;
}

prog.cpp: In function ‘int main()’:
prog.cpp:13:29:   in constexpr expansion of ‘operator""_int(((const char*)"ABC"), 3ul)’
prog.cpp:7:52: error: expression ‘<throw-expression>’ is not a constant-expression
     return (len == 2) ? s[0] | (s[1] << 8) : throw "len must be 2!";
                                                    ^~~~~~~~~~~~~~~~

Standard output is empty