diff mbox

[v4] Ensure mktime sets errno on error (bug 23789)

Message ID 9947f682-fc46-f2d6-4b07-536c03b9e657@cs.ucla.edu
State New, archived
Headers show

Commit Message

Paul Eggert Nov. 3, 2018, 2:13 a.m. UTC
[cc'ing to bug-gnulib since mktime.c is shared with gnulib]

In <https://www.sourceware.org/ml/libc-alpha/2018-10/msg00662.html> Albert 
ARIBAUD (3ADEV) wrote:

>   	 useful than returning -1.  */
>         goto offset_found;
>       else if (--remaining_probes == 0)
> -      return -1;
> +      {
> +	__set_errno (EOVERFLOW);
> +	return -1;
> +      }

There should be no need to set errno here, since localtime_r or gmtime_r should 
have already set errno. And setting errno to EOVERFLOW would be a mistake if 
localtime_r or gmtime_r set errno to some value other than EOVERFLOW. 
Conversely, guess_time_tm should set errno on overflow error.

>     /* We have a match.  Check whether tm.tm_isdst has the requested
>        value, if any.  */
> @@ -507,7 +511,10 @@ __mktime_internal (struct tm *tp,
>         if (INT_ADD_WRAPV (t, sec_adjustment, &t)
>   	  || ! (mktime_min <= t && t <= mktime_max)
>   	  || ! convert_time (convert, t, &tm))
> -	return -1;
> +	{
> +	  __set_errno (EOVERFLOW);
> +	  return -1;
> +	}

Similarly, this should not set errno if ! convert_time (convert, t, &tm) since 
convert_time should set errno on failure and we shouldn't second-guess it.

> @@ -522,13 +529,12 @@ __mktime_internal (struct tm *tp,
>   time_t
>   mktime (struct tm *tp)
>   {
> +# if defined _LIBC || NEED_MKTIME_WORKING
> +  static mktime_offset_t localtime_offset;
>     /* POSIX.1 8.1.1 requires that whenever mktime() is called, the
>        time zone names contained in the external variable 'tzname' shall
>        be set as if the tzset() function had been called.  */
>     __tzset ();
> -
> -# if defined _LIBC || NEED_MKTIME_WORKING
> -  static mktime_offset_t localtime_offset;
>     return __mktime_internal (tp, __localtime_r, &localtime_offset);
>   # else
>   #  undef mktime

Come to think of it, this part of the change is not needed. The glibc 
documentation already says that mktime (p) updates *p only if mktime succeeds. 
So a caller that wants to determine whether a mktime that returned ((time_t) -1) 
succeeded merely needs to (say) set p->tm_wday = -1 before calling mktime (p), 
and then test whether p->tm_wday is still negative after mktime returns. So 
there is no need for mktime to save and restore errno after all.

So, I propose that we install the following patches instead:

1. Apply the first attached patch to glibc.

2. Apply the second attached patch to Gnulib, so that its mktime.c stays in sync 
with glibc.

3. Please construct a third patch containing your mktime test case for glibc, 
and we then apply that patch to glibc.
diff mbox

Patch

From 96e52c5786964954e41e3242b5342a9462f6fa78 Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Fri, 2 Nov 2018 18:48:57 -0700
Subject: [PATCH] mktime: fix EOVERFLOW bug

This fixes a glibc bug I reported here:
https://sourceware.org/bugzilla/show_bug.cgi?id=23789
* lib/mktime.c: Sync from glibc, incorporating the following:
[!_LIBC && !DEBUG_MKTIME]:
Include libc-config.h, not config.h, for __set_errno.
(guess_time_tm, __mktime_internal): Set errno to EOVERFLOW on overflow.
* m4/mktime.m4 (gl_FUNC_MKTIME_WORKS):
Check for EOVERFLOW bug in glibc 2.28 and earlier.
* modules/mktime (Depends-on): Add libc-config.
---
 ChangeLog      | 11 +++++++++++
 lib/mktime.c   | 21 +++++++++++++++------
 m4/mktime.m4   |  5 ++++-
 modules/mktime |  1 +
 4 files changed, 31 insertions(+), 7 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index bbf379b8c..2ce3520fb 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,16 @@ 
 2018-11-02  Paul Eggert  <eggert@cs.ucla.edu>
 
+	mktime: fix EOVERFLOW bug
+	This fixes a glibc bug I reported here:
+	https://sourceware.org/bugzilla/show_bug.cgi?id=23789
+	* lib/mktime.c: Sync from glibc, incorporating the following:
+	[!_LIBC && !DEBUG_MKTIME]:
+	Include libc-config.h, not config.h, for __set_errno.
+	(guess_time_tm, __mktime_internal): Set errno to EOVERFLOW on overflow.
+	* m4/mktime.m4 (gl_FUNC_MKTIME_WORKS):
+	Check for EOVERFLOW bug in glibc 2.28 and earlier.
+	* modules/mktime (Depends-on): Add libc-config.
+
 	gnulib-common.m4: port _Noreturn to C++
 	Problem reported by Akim Demaille in:
 	https://lists.gnu.org/r/bug-bison/2018-10/msg00067.html
diff --git a/lib/mktime.c b/lib/mktime.c
index 00f0dec6b..26f7a2751 100644
--- a/lib/mktime.c
+++ b/lib/mktime.c
@@ -39,7 +39,7 @@ 
  */
 
 #if !defined _LIBC && !DEBUG_MKTIME
-# include <config.h>
+# include <libc-config.h>
 #endif
 
 /* Assume that leap seconds are possible, unless told otherwise.
@@ -51,6 +51,7 @@ 
 
 #include <time.h>
 
+#include <errno.h>
 #include <limits.h>
 #include <stdbool.h>
 #include <stdlib.h>
@@ -255,8 +256,9 @@  long_int_avg (long_int a, long_int b)
    If TP is null, return a value not equal to T; this avoids false matches.
    YEAR and YDAY must not be so large that multiplying them by three times the
    number of seconds in a year (or day, respectively) would overflow long_int.
-   If the returned value would be out of range, yield the minimal or
-   maximal in-range value, except do not yield a value equal to T.  */
+   If TP is non-null and the returned value would be out of range, set
+   errno to EOVERFLOW and yield a minimal or maximal in-range value
+   that is not equal to T.  */
 static long_int
 guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
 	       long_int t, const struct tm *tp)
@@ -269,9 +271,10 @@  guess_time_tm (long_int year, long_int yday, int hour, int min, int sec,
 			       tp->tm_hour, tp->tm_min, tp->tm_sec);
       if (! INT_ADD_WRAPV (t, d, &result))
 	return result;
+      __set_errno (EOVERFLOW);
     }
 
-  /* Overflow occurred one way or another.  Return the nearest result
+  /* An error occurred, probably overflow.  Return the nearest result
      that is actually in range, except don't report a zero difference
      if the actual difference is nonzero, as that would cause a false
      match; and don't oscillate between two values, as that would
@@ -344,6 +347,8 @@  ranged_convert (struct tm *(*convert) (const time_t *, struct tm *),
    Use *OFFSET to keep track of a guess at the offset of the result,
    compared to what the result would be for UTC without leap seconds.
    If *OFFSET's guess is correct, only one CONVERT call is needed.
+   If successful, set *TP to the canonicalized struct tm;
+   otherwise leave *TP alone, return ((time_t) -1) and set errno.
    This function is external because it is used also by timegm.c.  */
 time_t
 __mktime_internal (struct tm *tp,
@@ -505,8 +510,12 @@  __mktime_internal (struct tm *tp,
       sec_adjustment -= sec;
       sec_adjustment += sec_requested;
       if (INT_ADD_WRAPV (t, sec_adjustment, &t)
-	  || ! (mktime_min <= t && t <= mktime_max)
-	  || ! convert_time (convert, t, &tm))
+	  || ! (mktime_min <= t && t <= mktime_max))
+	{
+	  __set_errno (EOVERFLOW);
+	  return -1;
+	}
+      if (! convert_time (convert, t, &tm))
 	return -1;
     }
 
diff --git a/m4/mktime.m4 b/m4/mktime.m4
index 4b3e399be..88f5dc92f 100644
--- a/m4/mktime.m4
+++ b/m4/mktime.m4
@@ -1,4 +1,4 @@ 
-# serial 30
+# serial 31
 dnl Copyright (C) 2002-2003, 2005-2007, 2009-2018 Free Software Foundation,
 dnl Inc.
 dnl This file is free software; the Free Software Foundation
@@ -43,6 +43,7 @@  AC_DEFUN([gl_FUNC_MKTIME_WORKS],
     [AC_RUN_IFELSE(
        [AC_LANG_SOURCE(
 [[/* Test program from Paul Eggert and Tony Leneis.  */
+#include <errno.h>
 #include <limits.h>
 #include <stdlib.h>
 #include <time.h>
@@ -150,6 +151,8 @@  bigtime_test (int j)
                   == (tm.tm_isdst < 0 ? -1 : 0 < tm.tm_isdst))))
         return 0;
     }
+  else if (errno != EOVERFLOW)
+    return 0;
   return 1;
 }
 
diff --git a/modules/mktime b/modules/mktime
index f08c5b14c..17ed3cd78 100644
--- a/modules/mktime
+++ b/modules/mktime
@@ -10,6 +10,7 @@  Depends-on:
 time
 multiarch
 intprops        [test $REPLACE_MKTIME = 1]
+libc-config     [test $REPLACE_MKTIME = 1]
 stdbool         [test $REPLACE_MKTIME = 1]
 time_r          [test $REPLACE_MKTIME = 1]
 verify          [test $REPLACE_MKTIME = 1]
-- 
2.19.1