[BUG]: Current Universal CRT on windows compilers appears out of date

[tjaurini]

Describe the bug

The current Universal C runtime on the website seems to still have the "round away from zero" bug. The IEEE standard since 1985 has been to "round to nearest even" or "banker's rounding" which reduces bias across aggregate calculations.

We only just noticed this bug at my office. The following C++ code on x64/x86 exhibits the issue, as it is part of the crt, not the compiler:

#include

int main () {
char str[30];
sprintf(str, "%.0lf", 2.5);
std::cout << str;
}

The output should be "2" but is still giving "3". I think this update is part of 21H2 but don't quote me on it. I have yet to find the change log.

Steps to reproduce

#include

// Type your code here, or load an example.
int main () {
char str[30];
sprintf(str, "%.0lf", 2.5);
std::cout << str;
}

Expected behavior

Output: 2

Reproduction link

Not applicable

Screenshots

Not applicable

Operating System

Windows 10

Browser version

Firefox 99.01

[mattgodbolt]

Hi! Can you please make a link so we can see what you're seeing? Thanks!

[OfekShilon]

@mattgodbolt I'm able to reproduce: https://godbolt.org/z/h3Pbarre3

[pmor13]

FYI: Fixed in 19.32.31302:

$ cat t67.cpp
#include <iostream>

int main () {
    char str[30];
    sprintf(str, "%.0lf", 2.5);
    std::cout << str;
}

$ cl t67.cpp /EHsc
Microsoft (R) C/C++ Optimizing Compiler Version 19.32.31302 for x64

$ ./t67.exe
2

Similar issue: https://stackoverflow.com/q/68851345/1778275.