Re: readdir is incorrectly implemented at Windows

On 2/25/19 10:38 AM, Konstantin Knizhnik wrote:
> Hi hackers,
>
> Small issue with readir implementation for Windows.
> Right now it returns ENOENT in case of any error returned by
> FindFirstFile.
> So all places in Postgres where opendir/listdir are used will assume
> that directory is empty and
> do nothing without reporting any error.
> It is not so good if directory is actually not empty but there are not
> enough permissions for accessing the directory and FindFirstFile
> returns ERROR_ACCESS_DENIED:
>
> struct dirent *
> readdir(DIR *d)
> {
>     WIN32_FIND_DATA fd;
>
>     if (d->handle == INVALID_HANDLE_VALUE)
>     {
>         d->handle = FindFirstFile(d->dirname, &fd);
>         if (d->handle == INVALID_HANDLE_VALUE)
>         {
>             errno = ENOENT;
>             return NULL;
>         }
>     }
>
>
> Attached please find small patch fixing the problem.
>

Diagnosis seems correct. I wonder if this is responsible for some odd
things we've seen over time on Windows.

This reads a bit oddly:

         {
-            errno = ENOENT;
+            if (GetLastError() == ERROR_FILE_NOT_FOUND)
+            {
+                /* No more files, force errno=0 (unlike mingw) */
+                errno = 0;
+                return NULL;
+            }
+            _dosmaperr(GetLastError());
             return NULL;
         }

Why not something like:

if (GetLastError() == ERROR_FILE_NOT_FOUND)
    errno = 0;
else
    _dosmaperr(GetLastError());
return NULL;

cheers

andrew

--
Andrew Dunstan https://www.2ndQuadrant.com
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