std :: stoul没有抛出std :: out_of_range

Question

Consider following code:

#include <iostream>
#include <cstring>
#include <cerrno>

int main() {
    unsigned long num = strtoul("0xFFFFFFFFFFFF11223344556677889900AABBCCDDEEFF", NULL, 16);
    std::cout << std::strerror(errno) << "\n";
    unsigned long num2 = std::stoul("0xFFFFFFFFFFFF11223344556677889900AABBCCDDEEFF");
    std::stoul("hello world");
    return 0;
}

This code is expected to print some "Out of range" from strerror and then to throw out_of_range exception according to documentation . It should never reach the last stoul line.

In practice, it does not throw on the second stoul statement. I have tried GCC 4.8.5 and MinGW 8.2.0, both failed to throw the out_of_range exception and only delivered invalid_argument on the last stoul statement.

Is this a bug that should be reported or am I missing something and this is expected behaviour?

Answer 1

Default base for std::stoul is 10.
stoul reads 0 , x is invalid so the rest of the string is ignored and numeric value 0 is returned.

Use similar syntax as in strtoul :

unsigned long num2 = std::stoul("0xFFFFFFFFFFFF11223344556677889900AABBCCDDEEFF", nullptr, 16);

Or with automatic deduction of numeric base:

unsigned long num2 = std::stoul("0xFFFFFFFFFFFF11223344556677889900AABBCCDDEEFF", nullptr, 0);

Both of the above versions will throw. See it online!