[perl #123495] Stop gmtime(nan) from crashing

We were getting a time struct like this:

$12 = {
  tm_sec = -2147483588,
  tm_min = 2147483647,
  tm_hour = -2147483624,
  tm_mday = -2147483647,
  tm_mon = 11,
  tm_year = 69,
  tm_wday = -2147483641,
  tm_yday = -2147483314,
  tm_isdst = 0,
  tm_gmtoff = 0,
  tm_zone = 0x1004f6bb6 "UTC"
}

which resulted in dayname[tmbuf.tm_wday] reading past the beginning
of the array.  We should check for nan explicitly instead of falling
through to the time calculations.

(cherry picked from commit d8bd3d828a02f8df716063d9980b8b9af539ca42)

1 files changed, 7 insertions, 1 deletions

diff --git a/pp_sys.c b/pp_sys.c
index a4172ac55d..af9cc844f1 100644
--- a/pp_sys.c
+++ b/pp_sys.c
@@ -4460,11 +4460,16 @@ PP(pp_gmtime)
     }
     else {
 	NV input = Perl_floor(POPn);
+	const bool isnan = Perl_isnan(input);
 	when = (Time64_T)input;
-	if (when != input) {
+	if (UNLIKELY(isnan || when != input)) {
 	    /* diag_listed_as: gmtime(%f) too large */
 	    Perl_ck_warner(aTHX_ packWARN(WARN_OVERFLOW),
 			   "%s(%.0" NVff ") too large", opname, input);
+	    if (isnan) {
+		err = NULL;
+		goto failed;
+	    }
 	}
     }
 
@@ -4490,6 +4495,7 @@ PP(pp_gmtime)
     if (err == NULL) {
 	/* diag_listed_as: gmtime(%f) failed */
 	/* XXX %lld broken for quads */
+      failed:
 	Perl_ck_warner(aTHX_ packWARN(WARN_OVERFLOW),
 		       "%s(%.0" NVff ") failed", opname, when);
     }