Open a directory with opendir(), change to it with chdir(), and then try
to get its contents with readdir(). readdir() will fail.
The reason for this is that readdir() uses the string supplied to opendir()
to reference the directory, not an absolute path or unique ID.

Change opendir.c to create a full path from the full or partial path given.
I cannot test this fix with LFNs; it should work, though, provided that
_fixpath handles LFNs. Could someone verify this, maybe?

diff file for \djgpp\src\libc\posix\dirent\opendir.c below.

5a6,7
> #include <limits.h>
> #include <sys/stat.h>
12a15
> 
16c19
<   dir->name = (char *)malloc(strlen(name)+6);
---
>   dir->name = (char *)malloc(PATH_MAX);
22d24
<   strcpy(dir->name, name);
26,27c28,34
<   /* Append a "." if we got only the device name */
<   if (dir->name[1] == ':' && dir->name[2] == 0)
---
>   /* Make absolute path */
> 
>   _fixpath (name, dir->name);
> 
>   /* Reduce memory footage to amount needed */
>   dir->name = (char *)realloc(dir->name, strlen(dir->name)+5);
>   if (dir->name == 0)
29,30c36,37
<     dir->name[2] = '.';
<     dir->name[3] = 0;
---
>     free(dir);
>     return 0;
53c60
<   dir->name[length++] = 0;
---
>   dir->name[length++] = '\0';

Teach me to use www without understanding it ... the last three lines of
the diff should read:

<   dir->name[length++] = 0;
---
>   dir->name[length++] = '\0';

(That's backslash-zero, in case I got it wrong again)

The realloc is really unnecessary, since the memory saved is trivial
if it was actually released, and it's not.  So this just makes the
code bigger, slower, and more complicated with no real benefit.  Other
than that, it looks like a good fix.  This appears to have been broken
when findfirst was moved from opendir to readdir.