Re: [Libguestfs] [libnbd PATCH] copy: Fail nbdcopy if NBD read or write fails

On 02/03/22 15:12, Eric Blake wrote: > On Thu, Feb 03, 2022 at 02:46:27PM +0200, Nir Soffer wrote: >> So we would use fprintf and strerror, and setting errno would be needed >> although it can be used with %m (is it portable?). > > %m is not portable in *printf(3). It IS portable in syslog(3), which > is why glibc printf(3) supports %m as well; and in nbdkit, we use a > printf wrapper on non-glibc to give unconditional %m support to nbdkit > plugins. But we do not have that printf wrapper here. Using > strerror() instead of perror() is doable in applications (we shouldn't > do it directly in libnbd since strerror() has multi-threaded > implications and we don't control what the application may be doing in > other threads, but in nbdcopy we control the entire application). Side topic: what do we think about strerror_r()?

... Hmmm I recall something... Yep: we now have guestfs_int_strerror() in the libguestfs-common project at least. (We cannot just copy it over I think, due to licence differences; however, with Rich having authored commit 9ec7cd8e23b5 ("utils: Fix usage of strerror_r", 2021-12-09), Red Hat seems to "own the copyright on that function" (if this statement makes any sense), so we could "relicense" it.)