On Mon, Jun 23, 2025 at 10:52 AM Corinna Vinschen <corinna-cyg...@cygwin.com> wrote: > > On Jun 20 13:33, Sebastian Feld wrote: > > On Fri, Jun 20, 2025 at 12:03 PM Johannes Schindelin > > <johannes.schinde...@gmx.de> wrote: > > > winsup/cygwin/path.cc | 21 ++++++++++++++++----- > > > 1 file changed, 16 insertions(+), 5 deletions(-) > > > > > > diff --git a/winsup/cygwin/path.cc b/winsup/cygwin/path.cc > > > index 42919a7cf5..ed08398930 100644 > > > --- a/winsup/cygwin/path.cc > > > +++ b/winsup/cygwin/path.cc > > > @@ -1855,9 +1855,18 @@ symlink_native (const char *oldpath, path_conv > > > &win32_newpath) > > > while (towupper (*++c_old) == towupper (*++c_new)) > > > > 1 unrelated issue: > > I think this towupper() code is WRONG if the filesystem (e.g. WSL) is > > case-sensitive! > > The preceding comment tries to explain why we always compare case > insensitive. There's a high probability that the symlink will be used > by native (non-Cygwin) processes which are insensitive.
OK, but this is at least bad for performance. Some stats from a profiling tool I am working on: German language, multibyte locale, codepage 65001: Each towupper() traverses 11 functions, covering between 8002 and 11722 instructions, and between 260 and 469 branches, on 64bit. If the code could just use the per-volume case sensitive flag, then this could be reduced to 20-30 instructions just to do the indirect load (2 times) and compare. > > How can code in cygwin.dll test whether the current path is on a > > case-sensitive volume, or not? > > There's a twist here. NTFS or ReFS or other filesystems (but not FAT) > are usually case sensitive. It's the OS which makes them case insensitve > by using a specific flag at open time, combined with a kernel registry > key. So apart from FAT, the creator of a file decides if it's created > sensitive or insensitive, and the one searching for and opening a file > is deciding if the search/open is sensitive or insensitive. > > Also, we're creating the symlink via CreateSymbolicLinkW, which is > probably acting case insensitive anyway... > > What if the perr-dir case-sensitive > > feature is ON, should that be probed and handled too? > > ...unless the symlink is created in a case sensitive dir, I assume. > > Right now we don't handle case sensitive dirs in the path_conv code. We > only check for the kernel registry key and the FILE_CASE_SENSITIVE_SEARCH > filesystem flag. > > To add the sensitive dirs to the picture, path_conv() would have to > check every directory on NTFS for > NtQueryInformationFile(FileCaseSensitiveInformation). It would then > set the path_conv::caseinsensitive flag accordingly. Yikes. Does Windows cache this per-dir info somewhere? Sebi -- Sebastian Feld - IT security consultant -- Problem reports: https://cygwin.com/problems.html FAQ: https://cygwin.com/faq/ Documentation: https://cygwin.com/docs.html Unsubscribe info: https://cygwin.com/ml/#unsubscribe-simple
