On Jun 6 17:57, Corinna Vinschen wrote: > > > On Wed, May 10, 2017 at 11:30:46AM +0200, Erik Bray wrote: > > >> [...] > > >> The attached test demonstrates the bug. Given an output buffer of N > > >> wide characters, wcsxfrm will cause bytes beyond the destination size > > >> to be reversed. I believe it might actually be a bug in the underlying > > >> LCMapStringW workhorse (this is on Windows 10; have not tested other > > >> versions). > > >> > > >> According to its docs [1], the cchDest argument (size of the > > >> destination buffer) is treated as a *byte* count when using > > >> LCMAP_SORTKEY. However, for the purposes of applying the > > >> LCMAP_BYTEREV transformation it seems to be treating the output size > > >> (in bytes) as character count. So in the example I give, where the > > >> output sort key is 7 bytes (including the null terminator), it swaps > > >> *14* bytes--the bytes including the sort key as well as the next 7 > > >> adjacent bytes. This is obviously a problem if the destination buffer > > >> is allocated out of some larger memory pool. > > >> > > >> This definitely has to be a bug, right? Or at least very poorly > > >> documented on MS's part. A workaround would either be to not use > > >> LCMAP_BYTEREV and just swap the bytes manually, or in a second call to > > >> LCMapStringW with LCMAP_BYTEREV and the correct character count... > > >> [...] > Incredible piece of detective work. Yeah, this looks very much like a > bug in LCMapStringW, embarrassingly one I didn't notice at the time of > writing the code. I just tested this on W7 and the problem was already > present. > > I don't know if this could be fixed by documentation. There's just no > safe way to combine LCMAP_SORTKEY with LCMAP_BYTEREV it seems, unless > you always allocate a buffer at least twice as big as actually required > for the sort key. > > So, yeah, I think manual swaping after calling LCMapStringW without > LCMAP_BYTEREV is the way to go. I'll prepare a fix. > > > Thanks for tracking down and the testcase, > Corinna
Latest snapshot from https://cygwin.com/snapshots/ has the patch applied. Please try. Thanks, Corinna -- Corinna Vinschen Please, send mails regarding Cygwin to Cygwin Maintainer cygwin AT cygwin DOT com Red Hat
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