Date: Thu, 18 Jan 2018 16:25:07 +0000 From: Adrián López Tejedor <adrianlzt@...il.com> To: musl@...ts.openwall.com Subject: Differences between strftime in musl and glibc Hi, I was having a problem parsing dates with python in an Alpine container and after some time digging I have found a difference in how musl and glibc calculate the unix Epoch using strftime. The format specifier to get the unix epoch is "%s", which is an extension of GNU ( https://www.gnu.org/software/libc/manual/html_node/Formatting-Calendar-Time.html ). In Glibc they use mktime ( https://github.com/bminor/glibc/blob/master/time/strftime_l.c#L1127), being this function aware of time zone. In musl is calculated without mktime, adding the seconds of each part of the tm struct ( https://git.musl-libc.org/cgit/musl/tree/src/time/strftime.c?h=v1.1.18#n132) and substracting the GMT offset. This method is unaware of the TZ data (I have not seen how to define that gmt offset when using strptime). Calling directly to musl/mktime work as expected. I have attached a small program which shows the difference between musl and glibc. Compiled with glibc: $ TZ=Europe/Madrid ./a.out strftime: -3600 mktime: -3600 $ TZ=America/New_York ./a.out strftime: 18000 mktime: 18000 Compiled with musl: $ TZ=Europe/Madrid ./a.out strftime: 0 mktime: -3600 $ TZ=America/New_York ./a.out strftime: 0 mktime: 18000 Thanks! Adrián Content of type "text/html" skipped View attachment "date_musl_glibc.c" of type "text/x-csrc" (498 bytes)
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