Problem with Simultaneous file access with JNI AND CYGWIN DLL only

[John Fralinger]

I have some more info on the following.  The Makefile
must be Makefile.cyg to demonstrate the problem!!!
The Mingw make works as expected.  It appears as if 
the cygwin dll may do something different when the
uid is not accessible.  ( getuid from a JNI returns
ffff )

Using Makfile.nocyg works as one would expect.

----- Original Message ----- 
From: John Fralinger <fralinjh@dca.net>
To: <cygwin@sourceware.cygnus.com>
Sent: Tuesday, August 10, 1999 11:52 AM
Subject: Simultaneous open of same file under JNI


The following code demonstrates where System V shared memory
is breaking.

It uses Mumit Khan's JNI example environment.

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <jni.h>
#include "HelloWorld.h"

JNIEXPORT void JNICALL 
Java_HelloWorld_displayHelloWorld (JNIEnv *env, jobject obj) 
{
  char *home;
  int fd;
  char resp[256];

  printf("Java JNI\n");
  home = getenv ("HOME");
  printf("HOME = %s\n", (home) ? home : "(NULL)");
  printf("Enter any existing file name (complete path) to open\n");
  gets( resp );
  if ( ( fd = open( resp, O_RDWR ) ) == -1 )
  perror( "open failed" );
  printf("Run again from another window BEFORE Enter to exit\n");
  printf("(Use the same file name to demonstrate problem)\n");
  gets( resp );
  return;
}

Shouldn't this work the same way when called from JNI????
When I run 2 of these to the same file I get Permission denied!

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