common: validate PLIST_DATE values before Time64_T conversion

Avoid undefined behavior when serializing malformed PLIST_DATE values
containing NaN, infinity, or values outside the Time64_T range. Add a
shared helper for checked date conversion and use it across writer paths.

1 files changed, 7 insertions, 0 deletions

diff --git a/src/time64.h b/src/time64.h
index 28968c0..2c20ffe 100644
--- a/src/time64.h
+++ b/src/time64.h
@@ -11,6 +11,13 @@ typedef long long       Int64;
 typedef Int64           Time64_T;
 typedef Int64           Year;
 
+#ifndef TIME64_MIN
+#define TIME64_MIN ((Time64_T)INT64_MIN)
+#endif
+
+#ifndef TIME64_MAX
+#define TIME64_MAX ((Time64_T)INT64_MAX)
+#endif
 
 /* A copy of the tm struct but with a 64 bit year */
 struct TM64 {