mktime: new test for mktime failure

[BZ#23789]
Based on a test suggested by Albert Aribaud in:
https://www.sourceware.org/ml/libc-alpha/2018-10/msg00662.html
* time/Makefile (tests): Add bug-mktime4.
* time/bug-mktime4.c: New file.

ChangeLog

@@ -1,5 +1,12 @@
 2018-11-15  Paul Eggert  <eggert@cs.ucla.edu>
 
+	mktime: new test for mktime failure
+	[BZ#23789]
+	Based on a test suggested by Albert Aribaud in:
+	https://www.sourceware.org/ml/libc-alpha/2018-10/msg00662.html
+	* time/Makefile (tests): Add bug-mktime4.
+	* time/bug-mktime4.c: New file.
+
 	mktime: fix EOVERFLOW bug
 	[BZ#23789]
 	* time/mktime.c [!_LIBC && !DEBUG_MKTIME]:

time/Makefile

@@ -43,7 +43,7 @@ tests	:= test_time clocktest tst-posixtz tst-strptime tst_wcsftime \
 	   tst-getdate tst-mktime tst-mktime2 tst-ftime_l tst-strftime \
 	   tst-mktime3 tst-strptime2 bug-asctime bug-asctime_r bug-mktime1 \
 	   tst-strptime3 bug-getdate1 tst-strptime-whitespace tst-ftime \
-	   tst-tzname tst-y2039
+	   tst-tzname tst-y2039 bug-mktime4
 
 include ../Rules
 

time/bug-mktime4.c

@@ -0,0 +1,92 @@
+#include <time.h>
+#include <errno.h>
+#include <limits.h>
+#include <stdbool.h>
+#include <stdio.h>
+#include <string.h>
+
+static bool
+equal_tm (struct tm const *t, struct tm const *u)
+{
+  return (t->tm_sec == u->tm_sec && t->tm_min == u->tm_min
+	  && t->tm_hour == u->tm_hour && t->tm_mday == u->tm_mday
+	  && t->tm_mon == u->tm_mon && t->tm_year == u->tm_year
+	  && t->tm_wday == u->tm_wday && t->tm_yday == u->tm_yday
+	  && t->tm_isdst == u->tm_isdst && t->tm_gmtoff == u->tm_gmtoff
+	  && t->tm_zone == u->tm_zone);
+}
+
+static int
+do_test (void)
+{
+  /* Calculate minimum time_t value.  This would be simpler with C11,
+     which has _Generic, but we cannot assume C11.  It would also
+     be simpler with intprops.h, which has TYPE_MINIMUM, but it's
+     better not to use glibc internals.  */
+  time_t time_t_min = -1;
+  time_t_min = (0 < time_t_min ? 0
+		: sizeof time_t_min == sizeof (long int) ? LONG_MIN
+		: sizeof time_t_min == sizeof (long long int) ? LLONG_MIN
+		: 1);
+  if (time_t_min == 1)
+    {
+      printf ("unknown time type\n");
+      return 1;
+    }
+  time_t ymin = time_t_min / 60 / 60 / 24 / 366;
+  bool mktime_should_fail = ymin == 0 || INT_MIN + 1900 < ymin + 1970;
+
+  struct tm tm0 = { .tm_year = INT_MIN, .tm_mday = 1, .tm_wday = -1 };
+  struct tm tm = tm0;
+  errno = 0;
+  time_t t = mktime (&tm);
+  long long int llt = t;
+  bool mktime_failed = tm.tm_wday == tm0.tm_wday;
+
+  if (mktime_failed)
+    {
+      if (! mktime_should_fail)
+	{
+	  printf ("mktime failed but should have succeeded\n");
+	  return 1;
+	}
+      if (errno == 0)
+	{
+	  printf ("mktime failed without setting errno");
+	  return 1;
+	}
+      if (t != (time_t) -1)
+	{
+	  printf ("mktime returned %lld but did not set tm_wday\n", llt);
+	  return 1;
+	}
+      if (! equal_tm (&tm, &tm0))
+	{
+	  printf ("mktime (P) failed but modified *P\n");
+	  return 1;
+	}
+    }
+  else
+    {
+      if (mktime_should_fail)
+	{
+	  printf ("mktime succeeded but should have failed\n");
+	  return 1;
+	}
+      struct tm *lt = localtime (&t);
+      if (lt == NULL)
+	{
+	  printf ("mktime returned a value rejected by localtime\n");
+	  return 1;
+	}
+      if (! equal_tm (lt, &tm))
+	{
+	  printf ("mktime result does not match localtime result\n");
+	  return 1;
+	}
+    }
+  return 0;
+}
+
+#define TIMEOUT 1000
+#include "support/test-driver.c"