[flang-commits] [flang] [flang] Update the date_and_time intrinsic for AIX (PR #104849)

[via flang-commits]

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@@ -247,6 +247,59 @@ static void DateAndTimeUnavailable(Fortran::runtime::Terminator &terminator,
 }
 
 #ifndef _WIN32
+#ifdef _AIX
+// Compute the time difference from GMT/UTC to get around the behavior of
+// strfname on AIX that requires setting an environment variable for numeric
+// value for ZONE.
+// The ZONE and the VALUES(4) arguments of the DATE_AND_TIME intrinsic has
+// the resolution to the minute.
+static int computeUTCDiff(const tm &localTime, bool *err) {
+  tm utcTime;
+  const time_t timer{mktime(const_cast<tm *>(&localTime))};
+  if (timer < 0) {
+    *err = true;
+    return 0;
+  }
+
+  // Get the GMT/UTC time
+  if (gmtime_r(&timer, &utcTime) == nullptr) {
+    *err = true;
+    return 0;
+  }
+
+  // Adjust for day difference
+  auto dayDiff{localTime.tm_mday - utcTime.tm_mday};
+  auto localHr{localTime.tm_hour};
+  if (dayDiff > 0) {
+    if (dayDiff == 1)
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jeanPerier wrote:

nit: if/then/else are always braced inside runtime code.

https://github.com/llvm/llvm-project/pull/104849