On Windows:

1. Create a directory with a very long name. For instance:

C:\abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz1234567890abcdefghijklmnopqrstuvwxyz12345

The path above takes 250 characters, which is close enough to the old Windows path length limit of 260 characters.

2. In LibreOffice, create a Writer document, and use File->Save As to attempt to save to the newly created long-name directory; a file name is irrelevant, may be a simple "1.odt".

This fails in 7.4 with "Error saving the document Untitled 1: Write Error. The file could not be written."

This succeeded in 7.3.

This is a regression from commit 92e835dbf00590c9c29509d2995cc7918a9bbb90
  Author Kunal Pawar <hellokunalpawar@gmail.com>
  Date   Fri Feb 18 19:15:04 2022 +0530
    tdf#98705 Replace GetCaseCorrectPathName with GetLongPathNameW

The failure happens in osl_getSystemPathFromFileURL_ called from osl_openFile called from File::open called from lcl_createName called from CreateTempName_Impl.

The problem is: GetCaseCorrectPathName didn't require that the path exists; GetLongPathNameW does. So the check "if ( nDecodedLen - nSkip <= MAX_PATH - 12 )" fails, and a branch involving GetLongPathNameW (previously GetCaseCorrectPathName) triggers; it now gives an empty string as a result (because, indeed, the file doesn't yet exist there).

It looks like we should re-implement the GetCaseCorrectPathName in some form, possibly using a combination of GetLongPathNameW and GetFullPathNameW, like this: first, try GetLongPathNameW; if it succeeds, return (and thus, keep the performance improvement we got in the fix for bug 98705); if it fails with "file does not exist", then use GetFullPathNameW to get the pointer to the last path segment, and repeat GetLongPathNameW with the path before the last segment, until we find a path segment that succeeds (so we get the correct case for the leading existing part, and keep the trailing non-existing part as is).