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emacs/m4/lstat.m4
Paul Eggert ae0d725005 [ChangeLog]
Work around some portability problems with symlinks.
* Makefile.in (GNULIB_MODULES): Add lstat, readlink, symlink.
* configure.in (lstat, HAVE_LSTAT): Remove special hack.
* lib/lstat.c, lib/readlink.c, lib/stat.c, lib/symlink.c:
* m4/dos.m4, m4/lstat.m4, m4/readlink.m4, m4/stat.m4, m4/symlink.m4:
New files, automatically generated from gnulib.
* aclocal.m4, configure, lib/Makefile.in, lib/gnulib.mk:
* lib/stdlib.in.h, m4/gl-comp.m4, m4/stdlib_h.m4: Regenerate.

2011-02-22  Paul Eggert  <eggert@cs.ucla.edu>
[src/ChangeLog]
Work around some portability problems with symlinks.
* fileio.c (Frename_file, Fmake_symbolic_link, Ffile_symlink_p):
Simplify the code by assuming that the readlink and symlink calls
exist, even if they always fail on this host.
(Ffile_readable_p): Likewise, for fifos.
* config.in: Regenerate.
2011-02-22 11:30:07 -08:00

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# serial 21
# Copyright (C) 1997-2001, 2003-2011 Free Software Foundation, Inc.
#
# This file is free software; the Free Software Foundation
# gives unlimited permission to copy and/or distribute it,
# with or without modifications, as long as this notice is preserved.
dnl From Jim Meyering.
AC_DEFUN([gl_FUNC_LSTAT],
[
AC_REQUIRE([gl_SYS_STAT_H_DEFAULTS])
dnl If lstat does not exist, the replacement <sys/stat.h> does
dnl "#define lstat stat", and lstat.c is a no-op.
AC_CHECK_FUNCS_ONCE([lstat])
if test $ac_cv_func_lstat = yes; then
AC_REQUIRE([AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK])
if test $ac_cv_func_lstat_dereferences_slashed_symlink = no; then
dnl Note: AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK does AC_LIBOBJ([lstat]).
REPLACE_LSTAT=1
fi
# Prerequisites of lib/lstat.c.
AC_REQUIRE([AC_C_INLINE])
else
HAVE_LSTAT=0
fi
])
# Redefine AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK, because it is no longer
# maintained in Autoconf.
AC_DEFUN([AC_FUNC_LSTAT_FOLLOWS_SLASHED_SYMLINK],
[
AC_CACHE_CHECK([whether lstat correctly handles trailing slash],
[ac_cv_func_lstat_dereferences_slashed_symlink],
[rm -f conftest.sym conftest.file
echo >conftest.file
if test "$as_ln_s" = "ln -s" && ln -s conftest.file conftest.sym; then
AC_RUN_IFELSE(
[AC_LANG_PROGRAM(
[AC_INCLUDES_DEFAULT],
[[struct stat sbuf;
/* Linux will dereference the symlink and fail, as required by
POSIX. That is better in the sense that it means we will not
have to compile and use the lstat wrapper. */
return lstat ("conftest.sym/", &sbuf) == 0;
]])],
[ac_cv_func_lstat_dereferences_slashed_symlink=yes],
[ac_cv_func_lstat_dereferences_slashed_symlink=no],
[# When cross-compiling, be pessimistic so we will end up using the
# replacement version of lstat that checks for trailing slashes and
# calls lstat a second time when necessary.
ac_cv_func_lstat_dereferences_slashed_symlink=no
])
else
# If the 'ln -s' command failed, then we probably don't even
# have an lstat function.
ac_cv_func_lstat_dereferences_slashed_symlink=no
fi
rm -f conftest.sym conftest.file
])
test $ac_cv_func_lstat_dereferences_slashed_symlink = yes &&
AC_DEFINE_UNQUOTED([LSTAT_FOLLOWS_SLASHED_SYMLINK], [1],
[Define to 1 if `lstat' dereferences a symlink specified
with a trailing slash.])
if test "x$ac_cv_func_lstat_dereferences_slashed_symlink" = xno; then
AC_LIBOBJ([lstat])
fi
])