** New features
-*** New macros AC_SYS_YEAR2038 and AC_SYS_YEAR2038_REQUIRED.
- These macros attempt to enlarge time_t to 64 bits, on systems where
- it has historically been only 32 bits wide, and therefore (assuming
- the usual Unix epoch) cannot represent dates after mid-January of
- 2038 (hence the names). The difference between the two is that
- AC_SYS_YEAR2038_REQUIRED unconditionally causes 'configure' to error
- out if 64-bit time_t is not available.
-
- AC_SYS_YEAR2038 will also error out if the host system shows signs of
- supporting dates after Jan 2038 (e.g. in file timestamps) but it can’t
- figure out how to get a wider time_t; this failure can be overridden
- with the --disable-year2038 option.
-
- Library authors should be cautious about adding these macros to
- their configure scripts; they can break binary backward compatibility.
-
-*** New macro AC_SYS_LARGEFILE_REQUIRED.
- This macro is the same as the existing AC_SYS_LARGEFILE except that
- it will cause 'configure' to error out if 64-bit off_t is not available,
- and it does not provide a --disable-largefile option.
-
-*** AC_SYS_LARGEFILE now optionally arranges to enlarge time_t.
- As an experimental measure to make it easier to rebuild old programs
- with support for dates after Jan 2038, if you regenerate any configure
- script that uses AC_SYS_LARGEFILE (but not AC_SYS_YEAR2038) using
- Autoconf 2.72, it will gain an --enable-year2038 option. When the
- program is configured with this option, time_t will be enlarged if
- possible, as if AC_SYS_YEAR2038 had been used.
-
- Using this option in a library build also potentially breaks binary
- backward compatibility.
+*** AC_SYS_LARGEFILE now optionally arranges to widen time_t.
+ It now causes 'configure' to gain an --enable-year2038 option which
+ widens time_t if possible on systems where time_t by default cannot
+ represent file timestamps and other timestamps after January 2038.
+ As with off_t, ino_t, etc., if library ABIs depend on time_t width,
+ applications should be configured consistently with libraries.
+
+*** New macro AC_SYS_YEAR2038.
+ This acts like AC_SYS_LARGEFILE, except that it causes 'configure'
+ to default to --enable-year2038. In a future Autoconf version,
+ AC_SYS_LARGEFILE is planned to do this too, so the two macros will
+ become equivalent.
*** AC_USE_SYSTEM_EXTENSIONS now enables C23 Annex F extensions
by defining __STDC_WANT_IEC_60559_EXT__.
@defmac AC_SYS_LARGEFILE
@acindex{SYS_LARGEFILE}
@cvindex _FILE_OFFSET_BITS
+@cvindex _TIME_BITS
@ovindex CC
@cindex Large file support
@cindex LFS
-If the default @code{off_t} type is a 32-bit integer, and therefore
-cannot be used to work with files larger than 4 gigabytes, arrange to
-make a larger @code{off_t} available, if the system supports this.
-Several other types related to the sizes of files and file systems will
-also be enlarged: @code{ino_t}, @code{blkcnt_t}, @code{fsblkcnt_t},
-@code{fsfilcnt_t}, and possibly @code{dev_t}.
-
-If a large @code{off_t} is available (whether or not any arrangements
-were necessary), the shell variable @code{ac_have_largefile} will be set
-to @samp{yes}; if not, it will be set to @samp{no}.
-
-Preprocessor macros will be defined if necessary to make a larger
-@code{off_t} available. (For example, on many systems the macro
-@code{_FILE_OFFSET_BITS} will be defined.) Some of these macros only
-work if they are defined before the first system header is included;
-therefore, when using this macro in concert with
-@code{AC_CONFIG_HEADERS}, make sure that @file{config.h} is included
-before any system headers.
-
-On a few older systems, the output variable @code{CC} will also be
-changed to add special compiler options that are needed to enable large
-@code{off_t}.
+If the default @code{off_t} type is a 32-bit integer so
+applications can deal only with files containing less than 2 GiB,
+make a wider @code{off_t} available if the system supports this.
+This may also widen several other types related to files and file
+systems, including @code{blkcnt_t}, @code{dev_t}, @code{ino_t},
+@code{fsblkcnt_t}, and @code{fsfilcnt_t}.
+
+Also, arrange for a @command{configure} option to request widening the
+type @code{time_t} as needed to represent file timestamps and other
+timestamps after January 2038. If year-2038 support is requested but
+@command{configure} fails to find a way to enable a wide @code{time_t}
+and inspection of the system suggests that this feature is available
+somehow, @command{configure} will error out.
+
+In this version of Autoconf, the year-2038 @command{configure} option
+currently defaults to @code{--disable-year2038}. If you want the
+default to be @code{--enable-year2038}, you can use
+@code{AC_SYS_YEAR2038} instead of @code{AC_SYS_LARGEFILE}. In other
+words, packages that use @code{AC_SYS_LARGEFILE} can be made ready for
+the year 2038 either by switching to @code{AC_SYS_YEAR2038}, or by
+configuring with @option{--enable-year2038}. A future version of
+Autoconf is planned to change the @code{AC_SYS_LARGEFILE} default to
+@code{--enable-year2038}; when that happens, @code{AC_SYS_LARGEFILE} and
+@code{AC_SYS_YEAR2038} will be equivalent. @xref{AC_SYS_YEAR2038}.
+
+Set the shell variable @code{ac_have_largefile} to to @samp{yes} or
+@code{no} depending on whether a wide @code{off_t} is available,
+regardless of whether arrangements were necessary. Similarly, set the
+shell variable @code{ac_have_year2038} to @code{yes} or @code{no}
+depending on whether a wide-enough @code{time_t} is available. If your
+package requires large-file or year-2038 support, you can use code like this:
+
+@example
+AS_IF([test $ac_have_year2038 = no],
+ [AC_MSG_FAILURE([year-2038 support missing])])
+@end example
+
+Define preprocessor macros if necessary to make types wider; For
+example, on many systems the macros @code{_FILE_OFFSET_BITS} and
+@code{_TIME_BITS} can be defined. Some of these macros work only if
+they are defined before the first system header is included; therefore,
+when using this macro in concert with @code{AC_CONFIG_HEADERS}, make
+sure that @file{config.h} is included before any system headers.
+
+On a few older systems, also change the output variable @code{CC} to add
+special compiler options that are needed to enable large @code{off_t}.
Large-file support can be disabled by configuring with the
-@option{--disable-largefile} option. Note that this has no effect on
-systems where @code{off_t} is 64 bits or larger by default. Disabling
-large-file support can have surprising effects, such as causing
-functions like @code{readdir} and @code{stat} to fail on small files
-(because their @emph{inode numbers} are unrepresentable).
+@option{--disable-largefile} option, and year-2038 support can
+be enabled and disabled via the @option{--enable-year2038} and
+@option{--disable-year2038} options. These options have no effect on
+systems where types are wide enough by default.
+Large-file support is required for year-2038 support: if you configure
+with @option{--disable-largefile} on a platform with 32-bit
+@code{time_t}, then year-2038 support is not available.
+
+Disabling large-file or year-2038 support can have surprising effects,
+such as causing functions like @code{readdir} and @code{stat} to fail
+even on small files because their inode numbers are unrepresentable, or
+causing functions like @code{stat} to fail because a file's timestamp is
+out of range.
Regardless of whether you use this macro, portable programs should not
assume that any of the types listed above fit into a @code{long int}.
-For example, it is not correct to print an arbitrary @code{off_t} value
-@code{X} with @code{printf ("%ld", (long int) X)}.
-
-Note that the standard C library functions @code{fseek} and @code{ftell}
-do not use @code{off_t}. If you need to use either of these functions,
-you should use @code{AC_FUNC_FSEEKO} as well as @code{AC_SYS_LARGEFILE},
-and then use their Posix replacements @code{fseeko} and @code{ftello},
-which @emph{do} use @code{off_t}, when available. @xref{AC_FUNC_FSEEKO}.
-
-As of Autoconf 2.72, @code{AC_SYS_LARGEFILE} also @emph{optionally}
-arranges to enlarge @code{time_t}. This is to make it easier to build
-programs that support timestamps after 2038; many configure scripts will
-not need to be modified, only regenerated with newer Autoconf. When
-@code{AC_SYS_LARGEFILE} is used, and @code{AC_SYS_YEAR2038} is
-@emph{not} used, @code{time_t} will normally be left at the system's
-default size, but you can request it be enlarged by configuring with the
-@option{--enable-year2038} option. (When @code{AC_SYS_YEAR2038} is also
-used, @code{time_t} is enlarged if possible. @xref{AC_SYS_YEAR2038}.)
-@end defmac
-
-@defmac AC_SYS_LARGEFILE_REQUIRED
-@acindex{SYS_LARGEFILE_REQUIRED}
-This macro has the same effect as @code{AC_SYS_LARGEFILE},
-but also declares that the program being configured
-@emph{requires} support for large files.
-If a large @code{off_t} is unavailable,
-@command{configure} will error out.
-The @option{--disable-largefile} option will not be available.
+For example, it is not portable to print an arbitrary @code{off_t} or
+@code{time_t} value @code{X} with @code{printf ("%ld", (long int) X)}.
+
+The standard C library functions @code{fseek} and @code{ftell} do not
+use @code{off_t}. If you need to use either of these functions, you
+should use @code{AC_FUNC_FSEEKO} as well as @code{AC_SYS_LARGEFILE}, and
+then use their Posix replacements @code{fseeko} and @code{ftello}.
+@xref{AC_FUNC_FSEEKO}.
+
+When using @code{AC_SYS_LARGEFILE} in different packages that are linked
+together and that have ABIs that depend on the width of @code{off_t},
+@code{time_t} or related types, the simplest thing is to configure all
+components the same way. For example, if an application uses
+@code{AC_SYS_LARGEFILE} and is configured with
+@option{--enable-year2038}, libraries it links to with an @code{off_t}-
+or @code{time_t}-dependent ABI should be configured equivalently.
+Alternatively, you can modify libraries to support both 32- and 64-bit
+ABIs though this is more work and typically few libraries other than the
+C library itself are modified in this way.
@end defmac
-
@anchor{AC_SYS_LONG_FILE_NAMES}
@defmac AC_SYS_LONG_FILE_NAMES
@acindex{SYS_LONG_FILE_NAMES}
@anchor{AC_SYS_YEAR2038}
@defmac AC_SYS_YEAR2038
@acindex{SYS_YEAR2038}
-@cvindex _TIME_BITS
@cindex Year 2038
-If the default @code{time_t} type is a signed 32-bit integer,
-and therefore (assuming the usual Unix epoch) cannot represent
-timestamps after mid-January of 2038, arrange to make a larger
-@code{time_t} available, if the system supports this.
-
-If a large @code{time_t} is available (whether or not any arrangements
-were necessary), the shell variable @code{ac_have_year2038} will be set
-to @samp{yes}; if not, it will be set to @samp{no}.
-
-Preprocessor macros will be defined if necessary to make a larger
-@code{time_t} available. (For example, on some systems the macro
-@code{_TIME_BITS} will be defined.) Some of these macros only work if
-they are defined before the first system header is included; therefore,
-when using this macro in concert with @code{AC_CONFIG_HEADERS}, make
-sure that @file{config.h} is included before any system headers.
-
-Support for timestamps after 2038 can be disabled by configuring with
-the @option{--disable-year2038} option. Note that this has no effect on
-systems where @code{time_t} is 64 bits or larger by default.
-If this option is @emph{not} given, and @command{configure} fails to
-find a way to enable a large @code{time_t}, but inspection of the
-system suggests that this feature is available @emph{somehow}, it will
-error out.
-
-Regardless of whether you use this macro, portable programs should not
-assume that @code{time_t} fits into @code{long int}. For example, it is
-not correct to print an arbitrary @code{time_t} value @code{X} with
-@code{printf ("%ld", (long int) X)}.
-
-@strong{Caution:} If you are developing a shared library, and
-@code{time_t} appears anywhere in your library's public interface, use
-of this macro may break binary compatibility with older executables.
-@end defmac
-
-@defmac AC_SYS_YEAR2038_REQUIRED
-@acindex{SYS_YEAR2038_REQUIRED}
-This macro has the same effect as @code{AC_SYS_YEAR2038},
-but also declares that the program being configured
-@emph{requires} support for timestamps after mid-January of 2038.
-If a large @code{time_t} is unavailable,
-@command{configure} will @emph{unconditionally} error out
-(unlike the behavior of @code{AC_SYS_YEAR2038}).
-The @option{--disable-year2038} option will not be available.
-
-@strong{Caution:} If you are developing a shared library, and
-@code{time_t} appears anywhere in your library's public interface, use
-of this macro may break binary compatibility with older executables.
+This is like @code{AC_SYS_LARGEFILE} except it defaults to enabling
+instead of disabling year-2038 support. @xref{AC_SYS_LARGEFILE}.
@end defmac
@node C and Posix Variants
["support not detected"],
[ac_have_year2038=no
AS_CASE([$enable_year2038],
- [required],
- [AC_MSG_FAILURE([support for timestamps after Jan 2038 is required])],
[yes],
[# If we're not cross compiling and 'touch' works with a large
# timestamp, then we can presume the system supports wider time_t
# --enable-year2038, or a --disable-year2038, or no option at all to
# the configure script. Note that this is expanded very late and
# therefore there cannot be any code in the AC_ARG_ENABLE. The
-# default value for `enable_year2038` is emitted unconditionally
+# default value for enable_year2038 is emitted unconditionally
# because the generated code always looks at this variable.
m4_define([_AC_SYS_YEAR2038_ENABLE],
[m4_divert_text([DEFAULTS],
- m4_provide_if([AC_SYS_YEAR2038_REQUIRED],
- [enable_year2038=required],
m4_provide_if([AC_SYS_YEAR2038],
[enable_year2038=yes],
- [enable_year2038=no])))]dnl
-[m4_provide_if([AC_SYS_YEAR2038_REQUIRED], [],
+ [enable_year2038=no]))]dnl
[AC_ARG_ENABLE([year2038],
m4_provide_if([AC_SYS_YEAR2038],
[AS_HELP_STRING([--disable-year2038],
- [omit support for dates after Jan 2038])],
+ [do not support timestamps after 2038])],
[AS_HELP_STRING([--enable-year2038],
- [include support for dates after Jan 2038])]))])])
+ [support timestamps after 2038])]))])
# _AC_SYS_YEAR2038_OPT_IN
# -----------------------
# On systems where time_t is not always 64 bits, this probe can be
# skipped by passing the --disable-year2038 option to configure.
AC_DEFUN([AC_SYS_YEAR2038],
-[m4_provide_if([AC_SYS_LARGEFILE_REQUIRED], [],
- [AC_REQUIRE([AC_SYS_LARGEFILE])])]dnl
+[AC_REQUIRE([AC_SYS_LARGEFILE])]dnl
[m4_provide_if([_AC_SYS_YEAR2038_PROBE], [], [dnl
AS_IF([test "$enable_year2038" != no], [_AC_SYS_YEAR2038_PROBE])
AC_CONFIG_COMMANDS_PRE([_AC_SYS_YEAR2038_ENABLE])
])])
-# AC_SYS_YEAR2038_REQUIRED
-# ------------------------
-# Same as AC_SYS_YEAR2038, but declares that this program *requires*
-# support for large time_t. If we cannot find any way to make time_t
-# capable of representing values larger than 2**31 - 1, configure will
-# error out. Furthermore, no --enable-year2038 nor --disable-year2038
-# option will be available.
-AC_DEFUN([AC_SYS_YEAR2038_REQUIRED],
-[m4_provide_if([AC_SYS_LARGEFILE_REQUIRED], [],
- [AC_REQUIRE([AC_SYS_LARGEFILE])])]dnl
-[m4_provide_if([_AC_SYS_YEAR2038_PROBE], [], [dnl
- _AC_SYS_YEAR2038_PROBE
- AC_CONFIG_COMMANDS_PRE([_AC_SYS_YEAR2038_ENABLE])
-])])
-
# _AC_SYS_LARGEFILE_TEST_CODE
# ---------------------------
# C code used to probe for large file support.
AS_CASE([$ac_cv_sys_largefile_opts],
["none needed"], [],
["support not detected"],
- [ac_have_largefile=no
- AS_IF([test $enable_largefile = required],
- [AC_MSG_FAILURE([support for large files is required])])],
+ [ac_have_largefile=no],
["-D_FILE_OFFSET_BITS=64"],
[AC_DEFINE([_FILE_OFFSET_BITS], [64],
# _AC_SYS_LARGEFILE_ENABLE
# ------------------------
-# Subroutine of AC_SYS_LARGEFILE. If AC_SYS_LARGEFILE_REQUIRED was
-# not used at any point in this configure script, add a
-# --disable-largefile option to the configure script. Note that this
+# Subroutine of AC_SYS_LARGEFILE. Note that this
# is expanded very late and therefore there cannot be any code in the
-# AC_ARG_ENABLE. The default value for `enable_largefile` is emitted
+# AC_ARG_ENABLE. The default value for enable_largefile is emitted
# unconditionally because the generated shell code always looks at
# this variable.
m4_define([_AC_SYS_LARGEFILE_ENABLE],
[m4_divert_text([DEFAULTS],
- m4_provide_if([AC_SYS_LARGEFILE_REQUIRED],
- [enable_largefile=required],
- [enable_largefile=yes]))]dnl
-[m4_provide_if([AC_SYS_LARGEFILE_REQUIRED], [],
+ enable_largefile=yes)]dnl
[AC_ARG_ENABLE([largefile],
- [AS_HELP_STRING([--disable-largefile], [omit support for large files])])])])
+ [AS_HELP_STRING([--disable-largefile], [omit support for large files])])])
# AC_SYS_LARGEFILE
# ----------------
# to have a 64-bit inode number cannot be accessed by 32-bit applications on
# Linux x86/x86_64. This can occur with file systems such as XFS and NFS.
# This macro allows configuration to continue if the system doesn't support
-# large files; see also AC_SYS_LARGEFILE_REQUIRED.
+# large files.
AC_DEFUN([AC_SYS_LARGEFILE],
[m4_provide_if([_AC_SYS_LARGEFILE_PROBE], [], [dnl
AS_IF([test "$enable_largefile" != no], [_AC_SYS_LARGEFILE_PROBE])
AC_CONFIG_COMMANDS_PRE([_AC_SYS_LARGEFILE_ENABLE])
])])
-# AC_SYS_LARGEFILE_REQUIRED
-# -------------------------
-# Same as AC_SYS_LARGEFILE, but declares that this program *requires*
-# support for large files. If we cannot find a combination of compiler
-# options and #defines that makes `off_t` capable of representing 2**63 - 1,
-# `configure` will error out. Furthermore, `configure` will not offer a
-# --disable-largefile command line option.
-# If both AC_SYS_LARGEFILE and AC_SYS_LARGEFILE_REQUIRED are used in the
-# same configure script -- in either order -- AC_SYS_LARGEFILE_REQUIRED wins.
-AC_DEFUN([AC_SYS_LARGEFILE_REQUIRED],
-[m4_provide_if([_AC_SYS_LARGEFILE_PROBE], [], [dnl
- _AC_SYS_LARGEFILE_PROBE
- AC_CONFIG_COMMANDS_PRE([_AC_SYS_LARGEFILE_ENABLE])
-])])
-
# AC_SYS_LONG_FILE_NAMES
# ----------------------
# Security: use a temporary directory as the most portable way of
projects / thirdparty / autoconf.git / commitdiff
