Re: ac_sys_largefile / fseeko problem

[Guido Draheim]

Paul Eggert schrieb:
> Guido Draheim <address@hidden> writes:
>
>
> > I am using
> > AC_SYS_LARGEFILE
> > AC_CHECK_FUNCS(ftello fseeko)
>
>
> Use AC_FUNC_FSEEKO rather than AC_CHECK_FUNCS(fseeko).
> That should work around your problems.

Thanks. However, that macro still calls the glibc
behavior a bug, which I think is simply true. The
glibc cvs stdio.h should be fixed, - atleast do export
fseeko when #def __USE_FILE_OFFSET64 is set!! - just in
order to avoid that silent callframe-mismatch. In other
words, export the REDIRECT atleast when a redirect-call
is required to make things to function properly.

This mode is easily achieved, in the glibc stdio.h part
on fseeko: delete the __USE_LARGEFILE ifdefs within the
#else-part opened by that #ifndef __USE_FILE_OFFSET64.

This minimal change is strictly required unless glibc
maintainers like to see the next program to delete some
large database with an innocent fseeko call of a
software ported to lfs mode running on a glibc system.
Note that C compilers wouldn't even warn about the
missing fseeko declaration unless -Wall or similar was
given.

# AC_FUNC_FSEEKO
# --------------
AC_DEFUN([AC_FUNC_FSEEKO],
[_AC_SYS_LARGEFILE_MACRO_VALUE(_LARGEFILE_SOURCE, 1,
   [ac_cv_sys_largefile_source],
   [Define to 1 to make fseeko visible on some hosts (e.g. glibc 2.2).],
   address@hidden:@include <stdio.h>], [return !fseeko;])

# We used to try defining _XOPEN_SOURCE=500 too, to work around a bug
# in glibc 2.1.3, but that breaks too many other things.
# If you want fseeko and ftello with glibc, upgrade to a fixed glibc.
AC_CACHE_CHECK([for fseeko], [ac_cv_func_fseeko],
[AC_LINK_IFELSE([AC_LANG_PROGRAM(address@hidden:@include <stdio.h>],
                                 [[return fseeko && fseeko (stdin, 0, 0);]])],
                [ac_cv_func_fseeko=yes],
                [ac_cv_func_fseeko=no])])
if test $ac_cv_func_fseeko = yes; then
  AC_DEFINE(HAVE_FSEEKO, 1,
    [Define to 1 if fseeko (and presumably ftello) exists and is declared.])
fi
])# AC_FUNC_FSEEKO