Mercurial > gnulib
changeset 39291:27f187a5e5d0
time_rz: work around Mac OS X 10.6 infloop
* doc/posix-functions/localtime.texi:
* doc/posix-functions/localtime_r.texi: Mention the bug.
* lib/time_rz.c (localtime_rz): Work around the bug. It’d be
better to fix localtime and localtime_r instead, but that would be
more work and is not needed to fix the Emacs problem.
* m4/time_rz.m4 (gl_TIME_RZ): Detect the bug.
author | Paul Eggert <eggert@cs.ucla.edu> |
---|---|
date | Mon, 26 Mar 2018 19:23:33 -0700 |
parents | 6c3d7fccbe2d |
children | f3e5ba124466 |
files | ChangeLog doc/posix-functions/localtime.texi doc/posix-functions/localtime_r.texi lib/time_rz.c m4/time_rz.m4 |
diffstat | 5 files changed, 69 insertions(+), 1 deletions(-) [+] |
line wrap: on
line diff
--- a/ChangeLog Sat Mar 24 09:48:47 2018 -0700 +++ b/ChangeLog Mon Mar 26 19:23:33 2018 -0700 @@ -1,3 +1,13 @@ +2018-03-26 Paul Eggert <eggert@cs.ucla.edu> + + time_rz: work around Mac OS X 10.6 infloop + * doc/posix-functions/localtime.texi: + * doc/posix-functions/localtime_r.texi: Mention the bug. + * lib/time_rz.c (localtime_rz): Work around the bug. It’d be + better to fix localtime and localtime_r instead, but that would be + more work and is not needed to fix the Emacs problem. + * m4/time_rz.m4 (gl_TIME_RZ): Detect the bug. + 2018-03-24 Jim Meyering <meyering@fb.com> test-version-etc.sh: don't use diff directly: use init.sh's compare
--- a/doc/posix-functions/localtime.texi Sat Mar 24 09:48:47 2018 -0700 +++ b/doc/posix-functions/localtime.texi Mon Mar 26 19:23:33 2018 -0700 @@ -16,6 +16,11 @@ Portability problems not fixed by Gnulib: @itemize @item +On some platforms, this function loops forever for values +near extrema (such as the year @math{-2**31}): +Mac OS X 10.6. +You can use the @code{time_rz} module to work around the problem. +@item On some platforms, this function returns nonsense values for unsupported arguments (like @math{2^56}), rather than failing: FreeBSD 10.
--- a/doc/posix-functions/localtime_r.texi Sat Mar 24 09:48:47 2018 -0700 +++ b/doc/posix-functions/localtime_r.texi Mon Mar 26 19:23:33 2018 -0700 @@ -22,7 +22,13 @@ Portability problems not fixed by Gnulib: @itemize -@item On some platforms, this function returns nonsense values for +@item +On some platforms, this function loops forever for values +near extrema (such as the year @math{-2**31}): +Mac OS X 10.6. +You can use the @code{time_rz} module to work around the problem. +@item +On some platforms, this function returns nonsense values for unsupported arguments (like @math{2^56}), rather than failing: FreeBSD 10. @end itemize
--- a/lib/time_rz.c Sat Mar 24 09:48:47 2018 -0700 +++ b/lib/time_rz.c Mon Mar 26 19:23:33 2018 -0700 @@ -286,6 +286,21 @@ struct tm * localtime_rz (timezone_t tz, time_t const *t, struct tm *tm) { +#ifdef HAVE_LOCALTIME_INFLOOP_BUG + /* The -67768038400665599 comes from: + https://lists.gnu.org/r/bug-gnulib/2017-07/msg00142.html + On affected platforms the greatest POSIX-compatible time_t value + that could return nonnull is 67768036191766798 (when + TZ="XXX24:59:59" it resolves to the year 2**31 - 1 + 1900, on + 12-31 at 23:59:59), so test for that too while we're in the + neighborhood. */ + if (! (-67768038400665599 <= *t && *t <= 67768036191766798)) + { + errno = EOVERFLOW; + return NULL; + } +#endif + if (!tz) return gmtime_r (t, tm); else
--- a/m4/time_rz.m4 Sat Mar 24 09:48:47 2018 -0700 +++ b/m4/time_rz.m4 Mon Mar 26 19:23:33 2018 -0700 @@ -13,6 +13,38 @@ AC_REQUIRE([gl_HEADER_TIME_H_DEFAULTS]) AC_REQUIRE([AC_STRUCT_TIMEZONE]) + # Mac OS X 10.6 loops forever with some time_t values less + # than -67768038400665599. See Bug#27706, Bug#27736, and + # https://lists.gnu.org/r/bug-gnulib/2017-07/msg00142.html + AC_CACHE_CHECK([whether localtime loops forever near extrema], + [gl_cv_func_localtime_infloop_bug], + [gl_cv_func_localtime_infloop_bug=no + AC_RUN_IFELSE( + [AC_LANG_PROGRAM( + [[#include <stdlib.h> + #include <string.h> + #include <unistd.h> + #include <time.h> + ]], [[ + time_t t = -67768038400665600; + struct tm *tm; + char *tz = getenv ("TZ"); + if (! (tz && strcmp (tz, "QQQ0") == 0)) + return 0; + alarm (2); + tm = localtime (&t); + /* Use TM and *TM to suppress over-optimization. */ + return tm && tm->tm_isdst; + ]])], + [TZ=QQQ0 ./conftest$EXEEXT || gl_cv_func_localtime_infloop_bug=yes], + [], + [gl_cv_func_localtime_infloop_bug="guessing no"])]) + if test "$gl_cv_func_localtime_infloop_bug" = yes; then + AC_DEFINE([HAVE_LOCALTIME_INFLOOP_BUG], 1, + [Define if localtime-like functions can loop forever on + extreme arguments.]) + fi + AC_CHECK_TYPES([timezone_t], [], [], [[#include <time.h>]]) if test "$ac_cv_type_timezone_t" = yes; then HAVE_TIMEZONE_T=1