Cygwin fread on Write-Only File Descriptor returns undefined state

[Linda Walsh <cygwin at tlinx dot org>]

I think I've run into a problem involving fread.
I open a test file (fopen) with Write-Only access ("w"),
immediately after that, I do an fread on the file handle
of some number of bytes. 

I expect fread to return an error.  But it doesn't. 
It returns 0 as the number of bytes read, and the
error value remains unset when querying with ferror.

In addition to fread not setting the error value, a value
of zero is returned.  Zero is to be returned, *only* on
end-of-file or error.  However, in the test case, neither
value is returned.  Theoretically, this shouldn't happen
(i.e. it's an undefined "set" of return values).

test program follows:
-------------------
#include <stdio.h>
main (int argc, char * argv[]) {

   FILE * output_handle=fopen("/tmp/tmpfile","w");
   if (!output_handle) {
       printf ("can't open output file /tmp/tmpfile\n");
       exit (1);
   }  

   char mybuff[4];
   int retval=fread(mybuff, sizeof(char), 4, output_handle);
   if (!retval) {
       int eof=feof(output_handle);
       int err=ferror(output_handle);
       printf ("(retval,eof,err) = (%d,%d,%d)\n",retval,eof,err);
       if (!eof && ! err) 
           printf ("Undefined error: fread returned zero, but there is 
no eof or error\n");
       exit(2);
   } else
       printf ("Unexpected success in fread: Read %d chars\n",retval);
  
   exit(0);
}
  

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