diff options
| -rw-r--r-- | ChangeLog | 12 | ||||
| -rw-r--r-- | m4/mktime.m4 | 28 |
2 files changed, 29 insertions, 11 deletions
@@ -1,3 +1,15 @@ +2006-12-22 Paul Eggert <eggert@cs.ucla.edu> + + * m4/mktime.m4 (AC_FUNC_MKTIME): Sync from Autoconf. + Include <limits.h>, and use its INT_MAX to rewrite the + j loop so that it does not overflow 'int'. Problem reported by + Ralf Wildenhues in + <http://lists.gnu.org/archive/html/bug-gnulib/2006-12/msg00084.html>. + Play it safe by shifting left by 1 rather than multiplying by 2, + as GCC is less likely to optimize this away when the value + is signed (when it assumes overflow leads to undefined behavior). + Also, don't assume time_t uses two's complement. + 2006-12-21 Paul Eggert <eggert@cs.ucla.edu> * MODULES.html.sh: New module wctype. diff --git a/m4/mktime.m4 b/m4/mktime.m4 index ffc05e4417..a65a369b19 100644 --- a/m4/mktime.m4 +++ b/m4/mktime.m4 @@ -1,4 +1,4 @@ -#serial 8 +#serial 9 dnl Copyright (C) 2002, 2003, 2005, 2006 Free Software Foundation, Inc. dnl This file is free software; the Free Software Foundation dnl gives unlimited permission to copy and/or distribute it, @@ -6,10 +6,10 @@ dnl with or without modifications, as long as this notice is preserved. dnl From Jim Meyering. -# Redefine AC_FUNC_MKTIME, to fix a bug in Autoconf 2.60a and earlier. +# Redefine AC_FUNC_MKTIME, to fix a bug in Autoconf 2.61a and earlier. # This redefinition can be removed once a new version of Autoconf is assumed. # The redefinition is taken from -# <http://cvs.sv.gnu.org/viewcvs/*checkout*/autoconf/lib/autoconf/functions.m4?rev=1.108&root=autoconf>. +# <http://cvs.sv.gnu.org/viewcvs/*checkout*/autoconf/autoconf/lib/autoconf/functions.m4?rev=1.119>. # AC_FUNC_MKTIME # -------------- AC_DEFUN([AC_FUNC_MKTIME], @@ -30,6 +30,7 @@ AC_CACHE_CHECK([for working mktime], ac_cv_func_working_mktime, # endif #endif +#include <limits.h> #include <stdlib.h> #ifdef HAVE_UNISTD_H @@ -178,12 +179,15 @@ main () isn't worth using anyway. */ alarm (60); - for (time_t_max = 1; 0 < time_t_max; time_t_max *= 2) - continue; - time_t_max--; - if ((time_t) -1 < 0) - for (time_t_min = -1; (time_t) (time_t_min * 2) < 0; time_t_min *= 2) - continue; + for (;;) + { + t = (time_t_max << 1) + 1; + if (t <= time_t_max) + break; + time_t_max = t; + } + time_t_min = - ((time_t) ~ (time_t) 0 == (time_t) -1) - time_t_max; + delta = time_t_max / 997; /* a suitable prime number */ for (i = 0; i < N_STRINGS; i++) { @@ -198,10 +202,12 @@ main () && mktime_test ((time_t) (60 * 60 * 24)))) return 1; - for (j = 1; 0 < j; j *= 2) + for (j = 1; ; j <<= 1) if (! bigtime_test (j)) return 1; - if (! bigtime_test (j - 1)) + else if (INT_MAX / 2 < j) + break; + if (! bigtime_test (INT_MAX)) return 1; } return ! (irix_6_4_bug () && spring_forward_gap () && year_2050_test ()); |