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Fixed possible precision loss in microtime

This is related to the fix for bug #64370. MSVC natively supports __int64 type,
so calculating with 32 bit ints is neither necessary nor reliable. Therefore
an older piece of code is reused.
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1 parent bb935ff commit b022e54bd100a914417e216d0872d3e67edecaf9 @weltling weltling committed Mar 23, 2013
Showing with 13 additions and 6 deletions.
  1. +13 −6 win32/time.c
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19 win32/time.c
@@ -50,6 +50,7 @@ int getfilesystemtime(struct timeval *tv)
FILETIME ft;
unsigned __int64 ff = 0;
MyGetSystemTimeAsFileTime timefunc;
+ ULARGE_INTEGER fft;
timefunc = get_time_func();
if (timefunc) {
@@ -58,14 +59,20 @@ int getfilesystemtime(struct timeval *tv)
GetSystemTimeAsFileTime(&ft);
}
- ff |= ft.dwHighDateTime;
- ff <<= 32;
- ff |= ft.dwLowDateTime;
- ff /= 10; /* convert to microseconds */
+ /*
+ * Do not cast a pointer to a FILETIME structure to either a
+ * ULARGE_INTEGER* or __int64* value because it can cause alignment faults on 64-bit Windows.
+ * via http://technet.microsoft.com/en-us/library/ms724284(v=vs.85).aspx
+ */
+ fft.HighPart = ft.dwHighDateTime;
+ fft.LowPart = ft.dwLowDateTime;
+ ff = fft.QuadPart;
+
+ ff /= 10Ui64; /* convert to microseconds */
ff -= 11644473600000000Ui64; /* convert to unix epoch */
- tv->tv_sec = (long)(ff / 1000000UL);
- tv->tv_usec = (long)(ff % 1000000UL);
+ tv->tv_sec = (long)(ff / 1000000Ui64);
+ tv->tv_usec = (long)(ff % 1000000Ui64);
return 0;
}

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