<chrono>: UB in year_month_day_last::day() when !ok() #1647
Description
Describe the bug
year_month_day_last::day() accesses an array without bounds check.
Lines 1511 to 1513 in 7f08bb3
Lines 1334 to 1343 in 7f08bb3
Other call sites of
_Last_day have checked _Month.ok() before calling, except year_month_day_last::day().
Returns: If
ok()istrue, [...]. Otherwise, the returned value is unspecified.
year_month_day_last::day() shouldn't invoke UB even if !ok().
Command-line test case
#include <chrono>
#include <iostream>
using namespace std;
using namespace std::chrono;
int main() {
cout << static_cast<unsigned int>((2020y / 0 / last).day()) << "\n";
return 0;
}C:\Users\He\source\test>cl /EHsc /W4 /std:c++latest ymd_last.cpp
用于 x64 的 Microsoft (R) C/C++ 优化编译器 19.28.29828 版
版权所有(C) Microsoft Corporation。保留所有权利。
/std:c++latest 作为最新的 C++
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而更改或移除。有关详细信息，请参阅
https://go.microsoft.com/fwlink/?linkid=2045807。
ymd_last.cpp
Microsoft (R) Incremental Linker Version 14.28.29828.0
Copyright (C) Microsoft Corporation. All rights reserved.
/out:ymd_last.exe
ymd_last.obj
C:\Users\He\source\test>.\ymd_last.exe
C:\Users\He\source\test>echo %ERRORLEVEL%
-1073741819
Expected behavior
Should print an unspecified value, but not crash.
STL version