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Improve doc for AC_SYS_LARGEFILE etc.

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Paul Eggert 2022-08-18 15:20:06 -07:00
parent 6dcecb780a
commit bc66c26f48
1 changed files with 13 additions and 5 deletions
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doc/autoconf.texi
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@ -8888,14 +8888,18 @@ if the system supports @samp{#!}, @samp{no} if not.
@cindex LFS
Arrange for 64-bit file offsets, known as
@uref{http://@/www.unix.org/@/version2/@/whatsnew/@/lfs20mar.html,
large-file support}. On some hosts, one must use special compiler
options to build programs that can access large files. Append any such
large-file support}, along with other large attributes.
On some hosts, one must use special compiler options
to build programs that can access files with large sizes inode
numbers, timestamps, or other attributes. Append any such
options to the output variable @code{CC}. Define
@code{_FILE_OFFSET_BITS}, @code{_LARGE_FILES}, and @code{_TIME_BITS}
if necessary.
Large-file support can be disabled by configuring with the
@option{--disable-largefile} option.
@option{--disable-largefile} option. If you disable large-file
support, your program may have trouble accessing arbitrary files, such
as files that might be found in an adversary's directory.
If you use this macro, check that your program works even when the types
@code{blkcnt_t}, @code{dev_t}, @code{ino_t}, @code{off_t}, and @code{time_t}
@ -8951,8 +8955,12 @@ not correct to print an arbitrary @code{time_t} value @code{X} with
concert with @code{AC_CONFIG_HEADERS}, be sure that @file{config.h} is
included before any system header.
Although @code{AC_SYS_LARGFILE} also widens @code{time_t} if possible,
it merely warns if this cannot be done, rather than reporting a fatal error.
@code{AC_SYS_LARGFILE} also widens @code{time_t} if possible,
as this is needed for programs that access files with large timestamps,
However, @code{AC_SYS_LARGEFILE} merely warns if @code{time_t} is too
narrow and cannot be widened, rather than reporting a fatal error as
@code{AC_SYS_YEAR2038} does. This is for portability to older
platforms that will become obsolete in the year 2038.
@end defmac
@node C and Posix Variants