** New features
-*** 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.
+*** 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.
+
+ Enlarging time_t to 64 bits is likely to have the side effect of
+ enlarging off_t and related types to 64 bits as well, as if you
+ had used AC_SYS_LARGEFILE. See the manual for details.
+
+ 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_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 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}.
+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}.
Large-file support can be disabled by configuring with the
-@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.
+@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).
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 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.
+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.
@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
-This is like @code{AC_SYS_LARGEFILE} except it defaults to enabling
-instead of disabling year-2038 support. @xref{AC_SYS_LARGEFILE}.
+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.
@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
+ [enable_year2038=no])))]dnl
+[m4_provide_if([AC_SYS_YEAR2038_REQUIRED], [],
[AC_ARG_ENABLE([year2038],
m4_provide_if([AC_SYS_YEAR2038],
[AS_HELP_STRING([--disable-year2038],
- [do not support timestamps after 2038])],
+ [omit support for dates after Jan 2038])],
[AS_HELP_STRING([--enable-year2038],
- [support timestamps after 2038])]))])
+ [include support for dates after Jan 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],
-[AC_REQUIRE([AC_SYS_LARGEFILE])]dnl
+[m4_provide_if([AC_SYS_LARGEFILE_REQUIRED], [],
+ [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],
+ [ac_have_largefile=no
+ AS_IF([test $enable_largefile = required],
+ [AC_MSG_FAILURE([support for large files is required])])],
["-D_FILE_OFFSET_BITS=64"],
[AC_DEFINE([_FILE_OFFSET_BITS], [64],
# _AC_SYS_LARGEFILE_ENABLE
# ------------------------
-# Subroutine of AC_SYS_LARGEFILE. Note that this
+# Subroutine of AC_SYS_LARGEFILE. If AC_SYS_LARGEFILE_REQUIRED was
+# not used at any point in this configure script, add a
+# --disable-largefile option to the configure script. Note that this
# is expanded very late and therefore there cannot be any code in the
-# AC_ARG_ENABLE. The default value for enable_largefile is emitted
+# AC_ARG_ENABLE. The default value for 'enable_largefile' is emitted
# unconditionally because the generated shell code always looks at
# this variable.
m4_define([_AC_SYS_LARGEFILE_ENABLE],
[m4_divert_text([DEFAULTS],
- enable_largefile=yes)]dnl
+ m4_provide_if([AC_SYS_LARGEFILE_REQUIRED],
+ [enable_largefile=required],
+ [enable_largefile=yes]))]dnl
+[m4_provide_if([AC_SYS_LARGEFILE_REQUIRED], [],
[AC_ARG_ENABLE([largefile],
- [AS_HELP_STRING([--disable-largefile], [omit support for large files])])])
+ [AS_HELP_STRING([--disable-largefile], [omit support for large files])])])])
# AC_SYS_LARGEFILE
# ----------------
# to have a 64-bit inode number cannot be accessed by 32-bit applications on
# Linux x86/x86_64. This can occur with file systems such as XFS and NFS.
# This macro allows configuration to continue if the system doesn't support
-# large files.
+# large files; see also AC_SYS_LARGEFILE_REQUIRED.
AC_DEFUN([AC_SYS_LARGEFILE],
[m4_provide_if([_AC_SYS_LARGEFILE_PROBE], [], [dnl
AS_IF([test "$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
