Eric Wong <e@xxxxxxxxx> writes: > Paul Eggert <eggert@xxxxxxxxxxx> wrote: >> Use gettimeofday instead of time(NULL) to get current time. >> This avoids clock skew on glibc 2.31+ on Linux, where in the >> first 1 to 2.5 ms of every second, time(NULL) returns a >> value that is one less than the tv_sec part of >> higher-resolution timestamps such as those returned by >> gettimeofday or timespec_get, or those in the file system. >> There are similar clock skew problems on AIX and MS-Windows, >> which have problems in the first 5 ms of every second. > > Wow, this is enlightening... and unfortunate :< > > I decided to check glibc archives to find more discussion on it. > So far, I've found: > > https://inbox.sourceware.org/libc-alpha/20230306160321.2942372-1-adhemerval.zanella@xxxxxxxxxx/T/ > > and the original bug: > https://sourceware.org/bugzilla/show_bug.cgi?id=30200 > > And this is due to the time64 changes in glibc 2.31+? > (<= 2.30 isn't affected?) > > <snip> > >> Yet another possibility would be to fix the Linux kernel so >> that the time syscall is consistent with the other timestamp >> syscalls. I suppose this has not been done due to >> performance implications. (Git's use of timestamps is rare >> enough that performance is not a significant consideration >> for git.) However, this wouldn't fix Git's problem on older >> Linux kernels, or on AIX or MS-Windows. > > Agreed on the older kernels and other OSes part. Yeah, this is interesting. I however wonder if we should follow our usual pattern of implementing git_time() with the identical function signature as what we replace (i.e. system's time()), and #undef/#define the symbol we replace with git_time, though. Wouldn't it make [1/2] a lot smaller and future-proof?
