From 96caee5e9a16b172611c6ead9df0ab39cb7acfa6 Mon Sep 17 00:00:00 2001 From: Paul Eggert Date: Mon, 26 Mar 2018 19:23:33 -0700 Subject: [PATCH] time_rz: work around Mac OS X 10.6 infloop MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit * 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. --- ChangeLog | 10 +++++++++ doc/posix-functions/localtime.texi | 5 +++++ doc/posix-functions/localtime_r.texi | 8 ++++++- lib/time_rz.c | 15 +++++++++++++ m4/time_rz.m4 | 32 ++++++++++++++++++++++++++++ 5 files changed, 69 insertions(+), 1 deletion(-) diff --git a/ChangeLog b/ChangeLog index 4b08908768..99f219c268 100644 --- a/ChangeLog +++ b/ChangeLog @@ -1,3 +1,13 @@ +2018-03-26 Paul Eggert + + 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 test-version-etc.sh: don't use diff directly: use init.sh's compare diff --git a/doc/posix-functions/localtime.texi b/doc/posix-functions/localtime.texi index 02d069cc1e..c8a2b83b06 100644 --- a/doc/posix-functions/localtime.texi +++ b/doc/posix-functions/localtime.texi @@ -16,6 +16,11 @@ when the environment variable @code{TZ} has been set by Cygwin. 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. diff --git a/doc/posix-functions/localtime_r.texi b/doc/posix-functions/localtime_r.texi index 6ca2aed6ce..4862cbfd69 100644 --- a/doc/posix-functions/localtime_r.texi +++ b/doc/posix-functions/localtime_r.texi @@ -22,7 +22,13 @@ HP-UX 10. 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 diff --git a/lib/time_rz.c b/lib/time_rz.c index 4682beb573..f9262c1720 100644 --- a/lib/time_rz.c +++ b/lib/time_rz.c @@ -286,6 +286,21 @@ revert_tz (timezone_t tz) 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 diff --git a/m4/time_rz.m4 b/m4/time_rz.m4 index 4378148978..af9fa02b57 100644 --- a/m4/time_rz.m4 +++ b/m4/time_rz.m4 @@ -13,6 +13,38 @@ AC_DEFUN([gl_TIME_RZ], 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 + #include + #include + #include + ]], [[ + 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 ]]) if test "$ac_cv_type_timezone_t" = yes; then HAVE_TIMEZONE_T=1 -- 2.39.5