s/dirent: Corrects a problem with opendir() noted by Petteri Aimonen in Bitbucket Issue 132: "opendir() fails for FAT filesystem with trailing slash in path":

I see the following behaviour on NuttX 7.26, where I have SD card mounted on /flash and a directory called "frm" on it:

opendir("/flash")  returns  (DIR *) 0x1000c580
opendir("/flash/") returns (DIR *) 0x1000c5d0
opendir("/flash/frm")  returns (DIR *) 0x1000c620
opendir("/flash/frm/")  returns (DIR *) 0x0

From POSIX specs for opendir(): "A pathname ... that ends with one or more trailing slashes shall be resolved as if a single dot character ( '.' ) were appended to the pathname."

So for mount points, opendir() works correctly, but for FAT32 filesystem it fails to open directory if the path has a trailing slash. I'm not quite sure how to cleanly fix this. Stripping the trailing slash in opendir() would require allocating a separate buffer, while fixing it in the FAT32 code seems somewhat complex due to the short/long filename logic.

It is not a big issue for me, I'm just going to fix it on the application side. But still a small portability and standards compliance issue.

NOTE: You would not see this problem if you call opendir() indirectly in NSH (like 'ls -R /') because NSH contains logic to remove trailing '/' characters from paths.

fs/dirent/fs_opendir.c

@@ -1,7 +1,8 @@
 /****************************************************************************
  * fs/dirent/fs_opendir.c
  *
- *   Copyright (C) 2007-2009, 2011, 2013-2014, 2017 Gregory Nutt. All rights reserved.
+ *   Copyright (C) 2007-2009, 2011, 2013-2014, 2017-2018 Gregory Nutt. All
+ *     rights reserved.
  *   Author: Gregory Nutt <gnutt@nuttx.org>
  *
  * Redistribution and use in source and binary forms, with or without
@@ -41,6 +42,7 @@
 
 #include <stdbool.h>
 #include <string.h>
+#include <ctype.h>
 #include <dirent.h>
 #include <assert.h>
 #include <errno.h>
@@ -230,9 +232,53 @@ FAR DIR *opendir(FAR const char *path)
 #ifndef CONFIG_DISABLE_MOUNTPOINT
   FAR const char *relpath = NULL;
 #endif
+  FAR char *alloc = NULL;
   bool isroot = false;
+  int len;
   int ret;
 
+  /* Strip off any trailing whitespace or '/' characters.  In this case we
+   * must make a copy of the user string so we can chop off bytes on the
+   * 'right' without modifying the user's const string.
+   */
+
+  if (path != NULL)
+    {
+      /* Length of the string excludes NUL terminator */
+
+      len = strlen(path);
+
+      /* Check for whitespace or a dangling '/' at the end of the string.
+       * But don't muck with the string any further if it has been reduced
+       * to "/"
+       */
+
+      while (len > 0 && strcmp(path, "/") != 0 &&
+             (isspace(path[len - 1]) || path[len - 1] == '/'))
+        {
+          /* Have we already allocated memory for the modified string? */
+
+          if (alloc == NULL)
+            {
+              alloc = strdup(path); /* Allocates one too many bytes */
+              if (alloc == NULL)
+                {
+                  ret = ENOMEM;
+                  goto errout;
+                }
+
+              /* Use the cloned, writable string instead of the user string */
+
+              path = alloc;
+            }
+
+          /* Chop off the final character */
+
+          len--;
+          alloc[len] = '\0';
+        }
+    }
+
   /* If we are given 'nothing' then we will interpret this as
    * request for the root inode.
    */
@@ -247,7 +293,7 @@ FAR DIR *opendir(FAR const char *path)
     }
   else
     {
-      /* We don't know what to do with relative pathes */
+      /* We don't know what to do with relative paths */
 
       if (*path != '/')
         {
@@ -362,6 +408,14 @@ FAR DIR *opendir(FAR const char *path)
 
   RELEASE_SEARCH(&desc);
   inode_semgive();
+
+  /* Free any allocated string memory */
+
+  if (alloc != NULL)
+    {
+      kmm_free(alloc);
+    }
+
   return ((FAR DIR *)dir);
 
   /* Nasty goto's make error handling simpler */
@@ -372,6 +426,15 @@ errout_with_direntry:
 errout_with_semaphore:
   RELEASE_SEARCH(&desc);
   inode_semgive();
+
+  /* Free any allocated string memory */
+
+  if (alloc != NULL)
+    {
+      kmm_free(alloc);
+    }
+
+errout:
   set_errno(ret);
   return NULL;
 }

fs/fat/fs_fat32.c

@@ -1622,8 +1622,7 @@ static int fat_opendir(FAR struct inode *mountpt, FAR const char *relpath,
         }
     }
 
-  fat_semgive(fs);
-  return OK;
+  ret = OK;
 
 errout_with_semaphore:
   fat_semgive(fs);