[1mdiff --git a/NEWS b/NEWS[m
[1mindex eafd7d69..0f71628d 100644[m
[1m--- a/NEWS[m
[1m+++ b/NEWS[m
[36m@@ -27,36 +27,33 @@[m [mGNU Autoconf NEWS - User visible changes.[m

** New features[m

*** New [31mmacros AC_SYS_YEAR2038 and AC_SYS_YEAR2038_REQUIRED.[m
[31m  These macros attempt[m[32mmacro AC_SYS_YEAR2038.[m
[32m  This causes 'configure'[m to [31menlarge[m[32mwiden[m time_t [31mto 64 bits,[m[32mif possible[m on systems where
  [31mit has historically been only 32 bits wide, and therefore (assuming[m
[31m  the usual Unix epoch)[m[32mtime_t by default[m cannot represent [31mdates[m[32mfile and other timestamps[m after
  [31mmid-January of[m
[31m  2038 (hence the names).  The difference between the two[m[32mJanuary 2038.  Widening[m is [31mthat[m
[31m  AC_SYS_YEAR2038_REQUIRED unconditionally causes 'configure' to error[m
[31m  out if 64-bit time_t is not available.[m

[31m  Enlarging time_t to 64 bits is likely to have the side effect of[m
[31m  enlarging off_t[m[32mpossible only on 32-bit GNU/Linux x86[m and
  [31mrelated types to 64 bits as well, as if you[m
[31m  had used AC_SYS_LARGEFILE.  See the manual for details.[m

[31m  Library authors should be cautious about adding these macros to[m
[31m  their[m[32mARM systems with glibc 2.34 or later.  To prevent widening,[m
  configure [31mscripts; they can break binary backward compatibility.[m

[31m*** New macro AC_SYS_LARGEFILE_REQUIRED.[m[32mwith --disable-year2038.[m

  This macro [31mis[m[32malso has[m the [31msame[m[32meffects[m as [31mthe existing AC_SYS_LARGEFILE except[m[32mAC_SYS_LARGEFILE, because in[m
[32m  practice time_t cannot be widened without large-file sypport.[m

[32m  Application and library builders should take care[m that [31mit will cause 'configure'[m[32mpackages[m
[32m  configured with --enable-year2038 and --disable-year2038 options[m
[32m  are configured consistently,[m to [31merror out if 64-bit off_t[m[32mavoid breaking binary compatibility.[m
[32m  This[m is [31mnot available,[m[32msimilar to longstanding consistency requirements with[m
[32m  --enable-largefile[m and [31mit does not provide a --disable-largefile option.[m[32m--disable-largefile.[m

*** AC_SYS_LARGEFILE now optionally arranges to [31menlarge[m[32mwiden[m time_t.
  [31mAs an experimental measure to make it easier[m[32mIt now acts like AC_SYS_YEAR2038, except 'configure' defaults[m to
  [31mrebuild old programs[m[32m--disable-year2038 unless AC_SYS_YEAR2038 is also present.[m
[32m  As[m with [31msupport for dates after Jan 2038, if you regenerate any[m[32mAC_SYS_YEAR2038, application and library builders should[m
  configure [31mscript that uses[m[32mconsistently.[m

[32m*** New macros AC_SYS_LARGEFILE_REQUIRED and AC_SYS_YEAR2038_REQUIRED.[m
[32m  These act like[m AC_SYS_LARGEFILE [31m(but not AC_SYS_YEAR2038) using[m
[31m  Autoconf 2.72, it will gain an --enable-year2038 option.  When the[m
[31m  program is configured with this option, time_t will be enlarged if[m
[31m  possible, as if[m[32mand[m AC_SYS_YEAR2038 [31mhad been used.[m

[31m  Using this option in a[m[32mrespectively,[m
[32m  except that they require large-file and year-2038 support respectively.[m
[32m  As with AC_SYS_YEAR2038, application and[m library [31mbuild also potentially breaks binary[m
[31m  backward compatibility.[m[32mbuilders should[m
[32m  configure consistently.[m

*** AC_USE_SYSTEM_EXTENSIONS now enables C23 Annex F extensions[m
  by defining __STDC_WANT_IEC_60559_EXT__.[m
[1mdiff --git a/doc/autoconf.texi b/doc/autoconf.texi[m
[1mindex df96280b..ce214284 100644[m
[1m--- a/doc/autoconf.texi[m
[1m+++ b/doc/autoconf.texi[m
[36m@@ -8798,71 +8798,109 @@[m [mif the system supports @samp{#!}, @samp{no} if not.[m
@defmac AC_SYS_LARGEFILE[m
@acindex{SYS_LARGEFILE}[m
@cvindex _FILE_OFFSET_BITS[m
[32m@cvindex _TIME_BITS[m
@ovindex CC[m
@cindex Large file support[m
@cindex LFS[m
If the default @code{off_t} type is a 32-bit integer,
and therefore cannot be used[31mto work[m with files [31mlarger than 4 gigabytes, arrange to[m[32m2 GiB or larger,[m
make a [31mlarger[m[32mwider[m @code{off_t} [31mavailable,[m[32mavailable[m if the system supports [31mthis.[m
[31mSeveral[m[32mit.[m
[32mSimilarly, widen[m other types related to[31mthe[m sizes of files and file systems
[31mwill[m
[31malso be enlarged: @code{ino_t},[m[32mif possible.  These types may include[m @code{blkcnt_t}, [32m@code{dev_t},[m
[32m@code{ino_t},[m @code{fsblkcnt_t}, @code{fsfilcnt_t}, and [31mpossibly @code{dev_t}.[m[32m@code{rlim_t}.[m

[32mAlso, arrange for a @command{configure} option @code{--enable-year2038}[m
[32mto request widening the type @code{time_t} as needed to represent file[m
[32mwand other timestamps after January 2038.  This widening is possible[m
[32monly on 32-bit GNU/Linux x86 and ARM systems with glibc 2.34 or later.[m
If [32myear-2038 support is requested but @command{configure} fails to find[m a [31mlarge @code{off_t}[m[32mway[m
[32mto widen @code{time_t} and inspection of the system suggests that[m
[32mthis feature[m is available [31m(whether[m[32msomehow, @command{configure} will error out.[m
[32mIf you want the default to be @code{--enable-year2038}, you can use[m
[32m@code{AC_SYS_YEAR2038} instead of @code{AC_SYS_LARGEFILE}.[m
[32mIn other words, older packages that have long used @code{AC_SYS_LARGEFILE}[m
[32mcan have year-2038 support on 32-bit GNU/Linux x86 and ARM systems either by[m
[32mregenerating @file{configure} with current Autoconf and configuring with[m
[32m@option{--enable-year2038},[m or [31mnot any arrangements[m
[31mwere necessary),[m[32mby using @code{AC_SYS_YEAR2038} and[m
[32mconfiguring without @option{--disable-year2038}.[m
[32mA future version of Autoconf might change the @code{AC_SYS_LARGEFILE}[m
[32mdefault to @code{--enable-year2038}; if and when that happens,[m
[32m@code{AC_SYS_LARGEFILE} and @code{AC_SYS_YEAR2038} will become equivalent.[m
[32m@xref{AC_SYS_YEAR2038}.[m

[32mSet[m the shell variable @code{ac_have_largefile}[31mwill be set[m to [31m@samp{yes}; if not, it will be[m[32mto @samp{yes} or[m
[32m@code{no} depending on whether a wide @code{off_t} is available,[m
[32mregardless of whether arrangements were necessary.[m
[32mSimilarly,[m set [32mthe shell variable @code{ac_have_year2038}[m to [31m@samp{no}.[m

[31mPreprocessor[m[32m@code{yes}[m
[32mor @code{no} depending on whether a wide-enough @code{time_t} is available.[m

[32mDefine preprocessor[m macros[31mwill be defined[m if necessary to make [31ma larger[m
[31m@code{off_t} available.  (For[m[32mtypes wider;[m
[32mfor[m example, on [31mmany[m[32mGNU/Linux[m systems the [31mmacro[m[32mmacros[m @code{_FILE_OFFSET_BITS}
[31mwill[m[32mand @code{_TIME_BITS} can[m be [31mdefined.)[m[32mdefined.[m  Some of these macros[31monly[m work [32monly[m if[31mthey are[m
defined before the first system header is included;
therefore, when using this macro in concert with[m
@code{AC_CONFIG_HEADERS}, make sure that @file{config.h} is included[m
before any system headers.[m

On [31ma few older[m[32mobsolete IRIX[m systems, [32malso change[m the output variable @code{CC}[31mwill also be[m
[31mchanged[m to
add[31mspecial[m compiler options[31mthat are[m needed [31mto enable large[m[32mfor wide[m @code{off_t}.

Large-file support can be disabled by configuring with the[m
@option{--disable-largefile} [31moption.  Note that this has[m[32moption, and year-2038 support can[m
[32mbe enabled and disabled via the @option{--enable-year2038} and[m
[32m@option{--disable-year2038} options.  These options have[m no effect on
systems where [31m@code{off_t} is 64 bits or larger[m[32mtypes are wide enough[m by default.
[32mLarge-file support is required for year-2038 support: if you configure[m
[32mwith @option{--disable-largefile} on a platform with 32-bit[m
[32m@code{time_t}, then year-2038 support is not available.[m

Disabling large-file [32mor year-2038[m support can have surprising effects,
such as causing functions like @code{readdir} and @code{stat} to fail
[32meven[m on [32ma[m small [31mfiles[m
[31m(because their @emph{inode numbers} are unrepresentable).[m[32mfile because its inode number or timestamp is out of range.[m

Regardless of whether you use this macro, portable programs should not[m
assume that any of the types listed above fit into a @code{long int}.[m
For example, it is not [31mcorrect[m[32mportable[m to print an arbitrary @code{off_t} [32mor[m
[32m@code{time_t}[m value @code{X} with @code{printf ("%ld", (long int) X)}.

[31mNote that the[m[32mThe[m standard C library functions @code{fseek} and @code{ftell}
do not use @code{off_t}.  If you need to use either of these functions,[m
you should use @code{AC_FUNC_FSEEKO} as well as @code{AC_SYS_LARGEFILE},[m
and then use their Posix replacements @code{fseeko} and [31m@code{ftello},[m
[31mwhich @emph{do} use @code{off_t}, when available.[m[32m@code{ftello}.[m
@xref{AC_FUNC_FSEEKO}.

[31mAs of Autoconf 2.72,[m[32mWhen using[m @code{AC_SYS_LARGEFILE} [31malso @emph{optionally}[m
[31marranges to enlarge @code{time_t}.  This[m[32min different packages that are linked[m
[32mtogether and that have interfaces that depend on the width of @code{off_t},[m
[32m@code{time_t} or related types, the simplest thing[m is to[31mmake it easier to build[m
[31mprograms that support timestamps after 2038; many[m configure [31mscripts will[m
[31mnot need to be modified, only regenerated with newer Autoconf.  When[m[32mall[m
[32mcomponents the same way.  For example, if an application uses[m
@code{AC_SYS_LARGEFILE}[31mis used,[m and[31m@code{AC_SYS_YEAR2038}[m is [31m@emph{not} used, @code{time_t} will normally[m[32mconfigured with[m
[32m@option{--enable-year2038}, libraries it links to with an @code{off_t}-[m
[32mor @code{time_t}-dependent interface should[m be [31mleft at the system's[m
[31mdefault size, but[m[32mconfigured equivalently.[m
[32mAlternatively,[m you can [31mrequest it be enlarged by configuring with the[m
[31m@option{--enable-year2038} option.  (When @code{AC_SYS_YEAR2038}[m[32mmodify libraries to support both 32- and 64-bit[m
[32minterfaces though this[m is [31malso[m
[31mused,[m[32mmore work and few libraries other than the C[m
[32mlibrary itself are modified in this way.[m

[32mApplications and libraries should be configured compatibly.[m
[32mIf @code{off_t},[m @code{time_t} [31mis enlarged[m[32mor related types appear in a library's[m
[32mpublic interface, enabling or disabling the library's large-file or[m
[32myear-2038 support may break binary compatibility with applications or[m
[32mwith other libraries.  Similarly,[m if [31mpossible.  @xref{AC_SYS_YEAR2038}.)[m[32man application links to a such a[m
[32mlibrary, enabling or disabling the application's large-file support may[m
[32mbreak binary compatibility with that library.[m
@end defmac[m

@defmac AC_SYS_LARGEFILE_REQUIRED[m
@acindex{SYS_LARGEFILE_REQUIRED}[m
This macro has the same effect as @code{AC_SYS_LARGEFILE},[m
but also declares that the program being configured[m
[31m@emph{requires}[m[32mrequires[m support for large files.
If a large @code{off_t} is unavailable,[m
@command{configure} will error out.[m
The @option{--disable-largefile} option will not be available.[m
[31m@end defmac[m

[32mLarge-file and year-2038 support for applications and libraries should[m
[32mbe configured compatibly.  @xref{AC_SYS_LARGEFILE}.[m
[32m@end defmac[m

@anchor{AC_SYS_LONG_FILE_NAMES}[m
@defmac AC_SYS_LONG_FILE_NAMES[m
[36m@@ -8885,55 +8923,24 @@[m [msystem.  If so, set the shell variable @code{ac_cv_sys_posix_termios} to[m
@anchor{AC_SYS_YEAR2038}[m
@defmac AC_SYS_YEAR2038[m
@acindex{SYS_YEAR2038}[m
[31m@cvindex _TIME_BITS[m
@cindex Year 2038[m
[31mIf the default @code{time_t} type[m[32mThis[m is [31ma signed 32-bit integer,[m
[31mand therefore (assuming the usual Unix epoch) cannot represent[m
[31mtimestamps after mid-January of 2038, arrange to make a larger[m
[31m@code{time_t} available, if the system supports this.[m

[31mIf a large @code{time_t} is available (whether or not any arrangements[m
[31mwere necessary), the shell variable @code{ac_have_year2038} will be set[m
[31mto @samp{yes}; if not,[m[32mlike @code{AC_SYS_LARGEFILE} except[m it [31mwill be set[m[32mdefaults[m to [31m@samp{no}.[m

[31mPreprocessor macros will be defined if necessary to make a larger[m
[31m@code{time_t} available.  (For example, on some systems the macro[m
[31m@code{_TIME_BITS} will be defined.)  Some[m[32menabling[m
[32minstead[m of [31mthese macros only work if[m
[31mthey are defined before the first system header is included; therefore,[m
[31mwhen using this macro in concert with @code{AC_CONFIG_HEADERS}, make[m
[31msure that @file{config.h} is included before any system headers.[m

[31mSupport[m[32mdisabling year-2038 support.  Year-2038 support[m for
[31mtimestamps after 2038 can be disabled by configuring with[m
[31mthe @option{--disable-year2038} option.  Note that this has no effect on[m
[31msystems where @code{time_t} is 64 bits or larger by default.[m
[31mIf this option is @emph{not} given,[m[32mapplications[m and [31m@command{configure} fails to[m
[31mfind a way to enable a large @code{time_t}, but inspection of the[m
[31msystem suggests that this feature is available @emph{somehow}, it will[m
[31merror out.[m

[31mRegardless of whether you use this macro, portable programs[m[32mlibraries[m should [31mnot[m
[31massume that @code{time_t} fits into @code{long int}.  For example, it is[m
[31mnot correct to print an arbitrary @code{time_t} value @code{X} with[m
[31m@code{printf ("%ld", (long int) X)}.[m

[31m@strong{Caution:} If you are developing a shared library, and[m
[31m@code{time_t} appears anywhere in your library's public interface, use[m
[31mof this macro may break binary compatibility with older executables.[m[32mbe configured compatibly.[m
[32m@xref{AC_SYS_LARGEFILE}.[m
@end defmac[m

@defmac AC_SYS_YEAR2038_REQUIRED[m
@acindex{SYS_YEAR2038_REQUIRED}[m
This macro has the same effect as @code{AC_SYS_YEAR2038},[m
but also declares that the program being configured[m
[31m@emph{requires}[m[32mrequires[m support for timestamps after mid-January of 2038.
If a large @code{time_t} is unavailable,[m
@command{configure} will [31m@emph{unconditionally}[m[32munconditionally[m error [31mout[m
[31m(unlike the behavior of @code{AC_SYS_YEAR2038}).[m[32mout.[m
The @option{--disable-year2038} option will not be available.[m

[31m@strong{Caution:} If you are developing a shared library,[m[32mYear-2038 support for applications[m and [31m@code{time_t} appears anywhere in your library's public interface, use[m
[31mof this macro may break binary compatibility with older executables.[m[32mlibraries should be configured[m
[32mcompatibly.  @xref{AC_SYS_YEAR2038}.[m
@end defmac[m

@node C and Posix Variants[m