From: Bruno Haible <bruno@clisp.org>
Date: Thu, 14 Aug 2025 20:16:23 +0000 (+0200)
Subject: lchmod: Use issymlink, issymlinkat.
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=2a98a9ae33269bf37f1825935959d6dd598eb2be;p=thirdparty%2Fgnulib.git

lchmod: Use issymlink, issymlinkat.

* lib/lchmod.c (lchmod): Use issymlink instead of readlink and
issymlinkat instead of readlinkat.
* modules/lchmod (Depends-on): Remove readlink. Add issymlink,
issymlinkat.
---

diff --git a/ChangeLog b/ChangeLog
index b69ff7406c..9df8c9b99b 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+2025-08-14  Bruno Haible  <bruno@clisp.org>
+
+	lchmod: Use issymlink, issymlinkat.
+	* lib/lchmod.c (lchmod): Use issymlink instead of readlink and
+	issymlinkat instead of readlinkat.
+	* modules/lchmod (Depends-on): Remove readlink. Add issymlink,
+	issymlinkat.
+
 2025-08-14  Bruno Haible  <bruno@clisp.org>
 
 	chown: Avoid a redundant stat() call.
diff --git a/lib/lchmod.c b/lib/lchmod.c
index aabb15e359..4c44ca8063 100644
--- a/lib/lchmod.c
+++ b/lib/lchmod.c
@@ -37,8 +37,6 @@
 int
 lchmod (char const *file, mode_t mode)
 {
-  char readlink_buf[1];
-
 #ifdef O_PATH
   /* Open a file descriptor with O_NOFOLLOW, to make sure we don't
      follow symbolic links, if /proc is mounted.  O_PATH is used to
@@ -49,17 +47,20 @@ lchmod (char const *file, mode_t mode)
     return fd;
 
   int err;
-  if (0 <= readlinkat (fd, "", readlink_buf, sizeof readlink_buf))
-    err = EOPNOTSUPP;
-  else if (errno == EINVAL)
-    {
-      static char const fmt[] = "/proc/self/fd/%d";
-      char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
-      sprintf (buf, fmt, fd);
-      err = chmod (buf, mode) == 0 ? 0 : errno == ENOENT ? -1 : errno;
-    }
-  else
-    err = errno == ENOENT ? -1 : errno;
+  {
+    int ret = issymlinkat (fd, "");
+    if (ret > 0)
+      err = EOPNOTSUPP;
+    else if (ret == 0)
+      {
+        static char const fmt[] = "/proc/self/fd/%d";
+        char buf[sizeof fmt - sizeof "%d" + INT_BUFSIZE_BOUND (int)];
+        sprintf (buf, fmt, fd);
+        err = chmod (buf, mode) == 0 ? 0 : errno == ENOENT ? -1 : errno;
+      }
+    else
+      err = errno == ENOENT ? -1 : errno;
+  }
 
   close (fd);
 
@@ -83,7 +84,7 @@ lchmod (char const *file, mode_t mode)
 
   /* O_PATH + /proc is not supported.  */
 
-  if (0 <= readlink (file, readlink_buf, sizeof readlink_buf))
+  if (issymlink (file) > 0)
     {
       errno = EOPNOTSUPP;
       return -1;
diff --git a/modules/lchmod b/modules/lchmod
index c087bfa00c..9caa756d21 100644
--- a/modules/lchmod
+++ b/modules/lchmod
@@ -6,14 +6,15 @@ lib/lchmod.c
 m4/lchmod.m4
 
 Depends-on:
+sys_stat-h
+extensions
 c99           [test $HAVE_LCHMOD = 0]
 errno-h       [test $HAVE_LCHMOD = 0]
-extensions
 fcntl-h       [test $HAVE_LCHMOD = 0]
 intprops      [test $HAVE_LCHMOD = 0]
+issymlink     [test $HAVE_LCHMOD = 0]
+issymlinkat   [test $HAVE_LCHMOD = 0]
 lstat         [test $HAVE_LCHMOD = 0]
-readlink      [test $HAVE_LCHMOD = 0]
-sys_stat-h
 unistd-h      [test $HAVE_LCHMOD = 0]
 
 configure.ac: