Fix error reporting by dupfd

[Eli Zaretskii]

The Bison 3.0.2 test suite failed in one test with a strange error
saying "_open_osfhandle failed: Too many open files".  Looking into
this, I found out that dupfd sets errno to EMFILE for no good reason:
_open_osfhandle itself sets errno, including to EMFILE if needed, so
there's no need to override that.  In this case, errno was EBADF, and
the code that called dup_noinherit was perfectly capable of dealing
with the consequences of that.

The patch to fix that is below.  While at that, I also took care of
TODO item regarding error codes from DuplicateHandle.

2014-10-07  Eli Zaretskii  <address@hidden>

        Fix error reporting by dupfd.
        * lib/fcntl.c (dupfd) [_WIN32]: Don't overwrite the value of
        errno set by _open_osfhandle by EMFILE.  Convert errors
        returned by DuplicateHandle to corresponding errno values.

--- lib/fcntl.c~0       2013-08-02 18:03:13 +0300
+++ lib/fcntl.c 2014-10-07 08:42:24 +0300
@@ -89,8 +89,25 @@ dupfd (int oldfd, int newfd, int flags)
                             inherit,                /* InheritHandle */
                             DUPLICATE_SAME_ACCESS)) /* Options */
         {
-          /* TODO: Translate GetLastError () into errno.  */
-          errno = EMFILE;
+          switch (GetLastError ())
+            {
+              case ERROR_TOO_MANY_OPEN_FILES:
+                errno = EMFILE;
+                break;
+              case ERROR_INVALID_HANDLE:
+              case ERROR_INVALID_TARGET_HANDLE:
+              case ERROR_DIRECT_ACCESS_HANDLE:
+                errno = EBADF;
+                break;
+              case ERROR_INVALID_PARAMETER:
+              case ERROR_INVALID_FUNCTION:
+              case ERROR_INVALID_ACCESS:
+                errno = EINVAL;
+                break;
+              default:
+                errno = EACCES;
+                break;
+            }
           result = -1;
           break;
         }
@@ -98,7 +115,6 @@ dupfd (int oldfd, int newfd, int flags)
       if (duplicated_fd < 0)
         {
           CloseHandle (new_handle);
-          errno = EMFILE;
           result = -1;
           break;
         }