[PATCH 0/5] drop non-reentrant time usage

gmtime/localtime is considered unsafe in multithread environment.

git was started as single-thread application, but we have some multi-thread code, right now.

replace all usage of gmtime/localtime by their respective reentrant ones.

On Linux (with both glibc and musl), we won't notice any differences in performance, since they implemented gmtime and gmtime_r mostly the same.

On Windows, we may be taxed, since gmtime_r and localtime_r is our compat functions, because we memcpy from returned data of gmtime/localtime.

To address that, I made patch #5 and included it together with this series. I'm not sure how much portable it is. It seems to run fine with my Windows 7 x86 and Windows 10 x64 VM, (inside git-sdk for Windows, if it matters). I'm Cc-ing j6t and Dscho on that patch to get their opinions.

Doan Tran Cong Danh (5):
  date.c::datestamp: switch to reentrant localtime_r
  date.c::time_to_tm_local: use reentrant localtime_r(3)
  date.c::time_to_tm: use reentrant gmtime_r(3)
  archive-zip: use reentrant localtime_r(3)
  mingw: use {gm,local}time_s as backend for {gm,local}time_r

 archive-zip.c  | 10 +++++-----
 compat/mingw.c | 13 +++++++------
 date.c         | 18 ++++++++++--------
 3 files changed, 22 insertions(+), 19 deletions(-)