On Tue, 23 Sep 2025, Pali Rohár wrote:
Function _gmtime64 is available since msvcr70.dll. For older msvcrt versions
provide emulation via WinAPI FileTimeToSystemTime() function which is
available on all Windows versions and takes 64-bit time value. To retrieve
thread local storage for gmtime return value (struct tm), use the
_gmtime32() function with dummy value.
---
mingw-w64-crt/Makefile.am | 2 ++
mingw-w64-crt/lib-common/msvcrt.def.in | 2 +-
mingw-w64-crt/misc/_gmtime64.c | 46 ++++++++++++++++++++++++++
3 files changed, 49 insertions(+), 1 deletion(-)
create mode 100644 mingw-w64-crt/misc/_gmtime64.c
+static const short int days_in_year[] = { -1, 30, 58, 89, 119, 150, 180, 211,
242, 272, 303, 333, 364 };
+
+static struct tm *__cdecl emu__gmtime64(const __time64_t *timeptr)
+{
+ struct tm *tmptr;
+ unsigned long long value;
+ FILETIME filetime;
+ SYSTEMTIME systemtime;
+
+ value = (*timeptr * 10000000) + 116444736000000000LL;
+ filetime.dwLowDateTime = value & 0xffffffff;
+ filetime.dwHighDateTime = value >> 32;
+ if (!FileTimeToSystemTime(&filetime, &systemtime))
+ return NULL;
+
+ /* retrieve thread local storage for gmtime tm */
+ tmptr = _gmtime32(&(__time32_t){0});
+ if (!tmptr)
+ return NULL;
+
+ tmptr->tm_sec = systemtime.wSecond;
+ tmptr->tm_min = systemtime.wMinute;
+ tmptr->tm_hour = systemtime.wHour;
+ tmptr->tm_mday = systemtime.wDay;
+ tmptr->tm_mon = systemtime.wMonth-1;
+ tmptr->tm_year = systemtime.wYear-1900;
Some spaces around the operator would make this more readable
+ tmptr->tm_wday = systemtime.wDayOfWeek;
+ tmptr->tm_yday = days_in_year[tmptr->tm_mon] + systemtime.wDay + ((systemtime.wMonth >= 3
&& ((systemtime.wYear % 4 == 0 && systemtime.wYear % 100 != 0) || systemtime.wYear % 400
== 0)) ? 1 : 0);
This expression is quite unwieldy; it would be much nicer with two
intermediate variables; leap_year and leap_day I think.
// Martin
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