X-Git-Url: http://erislabs.net/gitweb/?a=blobdiff_plain;f=m4%2Flink-follow.m4;h=d2c5dd998eb189e315e00525786e7c4147a97d1b;hb=12a64eb033ac96ccc78f96d66067c70be7d2be90;hp=45f189ef1fc424699e04cc4fe8325375969c2d5c;hpb=23fe10e274cf20fb2cb75ea1da9556a733106657;p=gnulib.git

diff --git a/m4/link-follow.m4 b/m4/link-follow.m4
index 45f189ef1..d2c5dd998 100644
--- a/m4/link-follow.m4
+++ b/m4/link-follow.m4
@@ -1,27 +1,37 @@
-#serial 4
-dnl Run a program to determine whether whether link(2) follows symlinks.
+# serial 15
+dnl Run a program to determine whether link(2) follows symlinks.
 dnl Set LINK_FOLLOWS_SYMLINKS accordingly.
 
-AC_DEFUN([gl_AC_FUNC_LINK_FOLLOWS_SYMLINK],
-[dnl
-  AC_CACHE_CHECK(
-    [whether link(2) dereferences a symlink specified with a trailing slash],
-		 jm_ac_cv_func_link_follows_symlink,
-  [
-    dnl poor-man's AC_REQUIRE: FIXME: repair this once autoconf-3 provides
-    dnl the appropriate framework.
-    test -z "$ac_cv_header_unistd_h" \
-      && AC_CHECK_HEADERS(unistd.h)
+# Copyright (C) 1999-2001, 2004-2006, 2009 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.
 
-    # Create a regular file.
-    echo > conftest.file
-    AC_TRY_RUN(
-      [
+dnl This macro can be used to emulate POSIX linkat.  If
+dnl LINK_FOLLOWS_SYMLINKS is 0, link matches linkat(,0), and
+dnl linkat(,AT_SYMLINK_FOLLOW) requires a readlink. If it is 1,
+dnl link matches linkat(,AT_SYMLINK_FOLLOW), and there is no way
+dnl to do linkat(,0) on symlinks (on all other file types,
+dnl link() is sufficient).  If it is -1, use a runtime test.
+AC_DEFUN([gl_FUNC_LINK_FOLLOWS_SYMLINK],
+[dnl
+  AC_CHECK_FUNCS_ONCE([readlink])
+  dnl Mingw lacks link, although gnulib provides a good replacement.
+  dnl However, it also lacks symlink, so there's nothing to test in
+  dnl the first place, and no reason to need to distinguish between
+  dnl linkat variants.  So, we set LINK_FOLLOWS_SYMLINKS to 0.
+  gl_link_follows_symlinks=0 # assume GNU behavior
+  if test $ac_cv_func_readlink = yes; then
+    AC_CACHE_CHECK([whether link(2) dereferences a symlink],
+		    gl_cv_func_link_follows_symlink,
+    [
+      # Create a regular file.
+      echo > conftest.file
+      AC_RUN_IFELSE([AC_LANG_SOURCE([[
 #       include <sys/types.h>
 #       include <sys/stat.h>
-#       ifdef HAVE_UNISTD_H
-#        include <unistd.h>
-#       endif
+#       include <unistd.h>
+#       include <stdlib.h>
 
 #       define SAME_INODE(Stat_buf_1, Stat_buf_2) \
 	  ((Stat_buf_1).st_ino == (Stat_buf_2).st_ino \
@@ -37,29 +47,35 @@ AC_DEFUN([gl_AC_FUNC_LINK_FOLLOWS_SYMLINK],
 
 	  /* Create a symlink to the regular file. */
 	  if (symlink (file, sym))
-	    abort ();
+	    return 2;
 
 	  /* Create a hard link to that symlink.  */
 	  if (link (sym, hard))
-	    abort ();
+	    return 3;
 
 	  if (lstat (hard, &sb_hard))
-	    abort ();
+	    return 4;
 	  if (lstat (file, &sb_file))
-	    abort ();
+	    return 5;
 
 	  /* If the dev/inode of hard and file are the same, then
 	     the link call followed the symlink.  */
-	  return SAME_INODE (sb_hard, sb_file) ? 0 : 1;
+	  return SAME_INODE (sb_hard, sb_file) ? 1 : 0;
 	}
-      ],
-      jm_ac_cv_func_link_follows_symlink=yes,
-      jm_ac_cv_func_link_follows_symlink=no,
-      jm_ac_cv_func_link_follows_symlink=yes dnl We're cross compiling.
-    )
-  ])
-  if test $jm_ac_cv_func_link_follows_symlink = yes; then
-    AC_DEFINE(LINK_FOLLOWS_SYMLINKS, 1,
-      [Define if `link(2)' dereferences symbolic links.])
+      ]])],
+	[gl_cv_func_link_follows_symlink=no], dnl GNU behavior
+	[gl_cv_func_link_follows_symlink=yes], dnl Followed link/compile failed
+	[gl_cv_func_link_follows_symlink=unknown] dnl We're cross compiling.
+      )
+      rm -f conftest.file conftest.sym conftest.hard
+    ])
+    case $gl_cv_func_link_follows_symlink in
+      yes) gl_link_follows_symlinks=1 ;;
+      no) ;; # already defaulted to 0
+      *) gl_link_follows_symlinks=-1 ;;
+    esac
   fi
+  AC_DEFINE_UNQUOTED([LINK_FOLLOWS_SYMLINKS], [$gl_link_follows_symlinks],
+    [Define to 1 if `link(2)' dereferences symbolic links, 0 if it
+     creates hard links to symlinks, and -1 if unknown.])
 ])