ResultException::what behaves incorrectly

It appears that it returns an empty string, at least in my particular case, on non-English Windows 10 system (Visual Studio Build Tools 2019).

The GetFailureLogString part actually works fine:

https://github.com/microsoft/wil/blob/3e2ee372dcbbe77977934fbe0c58ff8ceb0236ee/include/wil/result_macros.h#L2639-L2644

I can get the full report from the created string, starting with the drive letter, e. g. "G:\\Test...".

The odd things start with this conversion from wchar_t to char array:

https://github.com/microsoft/wil/blob/3e2ee372dcbbe77977934fbe0c58ff8ceb0236ee/include/wil/result_macros.h#L2646-L2647

In this newly created messageA string Instead of the drive letter I get the null terminating character, the rest of it appears to be fine, e. g. its contents are - "(null terminating character here):\\Test...". Because this string starts with the null terminating character now, the subsequent call of strlen(messageA) returns zero, and nothing valuable is written to the buffer:

https://github.com/microsoft/wil/blob/3e2ee372dcbbe77977934fbe0c58ff8ceb0236ee/include/wil/result_macros.h#L2648

Start in include/wil/result_macros.h at the GetFailureLogString and ResultException::what code around lines 2639-2648, focusing on the wchar_t-to-char conversion and subsequent strlen call. Reproduce the behavior on a non-English Windows system or inspect the existing conversion path; done means what() preserves the full failure message instead of returning an empty string.