linkat: Work around AIX 7.1 bug.

[gnulib.git] / lib / linkat.c

diff --git a/lib/linkat.c b/lib/linkat.c
index f785d09..73b1e3e 100644 (file)
--- a/lib/linkat.c
+++ b/lib/linkat.c
@@ -1,5 +1,5 @@
 /* Create a hard link relative to open directories.
-   Copyright (C) 2009 Free Software Foundation, Inc.
+   Copyright (C) 2009-2010 Free Software Foundation, Inc.
 
    This program is free software: you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
@@ -23,6 +23,7 @@
 #include <errno.h>
 #include <fcntl.h>
 #include <limits.h>
+#include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 #include <sys/stat.h>
@@ -188,83 +189,6 @@ linkat (int fd1, char const *file1, int fd2, char const *file2, int flag)
 
 # undef linkat
 
-/* Read a symlink, like areadlink, but relative to FD.  */
-
-static char *
-areadlinkat (int fd, char const *filename)
-{
-  /* The initial buffer size for the link value.  A power of 2
-     detects arithmetic overflow earlier, but is not required.  */
-# define INITIAL_BUF_SIZE 1024
-
-  /* Allocate the initial buffer on the stack.  This way, in the common
-     case of a symlink of small size, we get away with a single small malloc()
-     instead of a big malloc() followed by a shrinking realloc().  */
-  char initial_buf[INITIAL_BUF_SIZE];
-
-  char *buffer = initial_buf;
-  size_t buf_size = sizeof (initial_buf);
-
-  while (1)
-    {
-      /* Attempt to read the link into the current buffer.  */
-      ssize_t link_length = readlinkat (fd, filename, buffer, buf_size);
-
-      /* On AIX 5L v5.3 and HP-UX 11i v2 04/09, readlink returns -1
-         with errno == ERANGE if the buffer is too small.  */
-      if (link_length < 0 && errno != ERANGE)
-        {
-          if (buffer != initial_buf)
-            {
-              int saved_errno = errno;
-              free (buffer);
-              errno = saved_errno;
-            }
-          return NULL;
-        }
-
-      if ((size_t) link_length < buf_size)
-        {
-          buffer[link_length++] = '\0';
-
-          /* Return it in a chunk of memory as small as possible.  */
-          if (buffer == initial_buf)
-            {
-              buffer = (char *) malloc (link_length);
-              if (buffer == NULL)
-                /* errno is ENOMEM.  */
-                return NULL;
-              memcpy (buffer, initial_buf, link_length);
-            }
-          else
-            {
-              /* Shrink buffer before returning it.  */
-              if ((size_t) link_length < buf_size)
-                {
-                  char *smaller_buffer = (char *) realloc (buffer, link_length);
-
-                  if (smaller_buffer != NULL)
-                    buffer = smaller_buffer;
-                }
-            }
-          return buffer;
-        }
-
-      if (buffer != initial_buf)
-        free (buffer);
-      buf_size *= 2;
-      if (SSIZE_MAX < buf_size || (SIZE_MAX / 2 < SSIZE_MAX && buf_size == 0))
-        {
-          errno = ENOMEM;
-          return NULL;
-        }
-      buffer = (char *) malloc (buf_size);
-      if (buffer == NULL)
-        /* errno is ENOMEM.  */
-        return NULL;
-    }
-}
-
 /* Create a link.  If FILE1 is a symlink, create a hardlink to the
    canonicalized file.  */
 
@@ -338,14 +262,38 @@ linkat_follow (int fd1, char const *file1, int fd2, char const *file2)
 int
 rpl_linkat (int fd1, char const *file1, int fd2, char const *file2, int flag)
 {
-  if (!flag)
-    return linkat (fd1, file1, fd2, file2, flag);
   if (flag & ~AT_SYMLINK_FOLLOW)
     {
       errno = EINVAL;
       return -1;
     }
 
+#if LINKAT_TRAILING_SLASH_BUG
+  /* Reject trailing slashes on non-directories.  */
+  {
+    size_t len1 = strlen (file1);
+    size_t len2 = strlen (file2);
+    if ((len1 && file1[len1 - 1] == '/')
+        || (len2 && file2[len2 - 1] == '/'))
+      {
+        /* Let linkat() decide whether hard-linking directories is legal.
+           If fstatat() fails, then linkat() should fail for the same reason;
+           if fstatat() succeeds, require a directory.  */
+        struct stat st;
+        if (fstatat (fd1, file1, &st, flag ? 0 : AT_SYMLINK_NOFOLLOW))
+          return -1;
+        if (!S_ISDIR (st.st_mode))
+          {
+            errno = ENOTDIR;
+            return -1;
+          }
+      }
+  }
+#endif
+
+  if (!flag)
+    return linkat (fd1, file1, fd2, file2, flag);
+
   /* Cache the information on whether the system call really works.  */
   {
     static int have_follow_really; /* 0 = unknown, 1 = yes, -1 = no */