Re: cygwin crashes when loading DLL

[Alan Thompson <athompson at alphatech dot com>]

Shaddy,

Here is another clue (?) to add to the confusion.

My original work involved a Java program which loaded a native DLL using JNI.  This worked fine using the tips from www.inonit.com.  Next, in order to make my stuff easier to fit into legacy apps, I changed it around using the JNI Invocation Interface.  Now, it is a C++ app, which creates a JVM (really, just loads the jvm.dll), then tries to load a 2nd DLL containing the C++ callback code (called from java code).  This works, BUT it will no longer run from within the ant script as before.

In the first case, I used the ant <java> task to run the java program which talked to C++ code via JNI - no problem.  As the examples I posted for you show, one can use the ant <exec> task to start the C++ program, which then creates the JVM via JNI - no problem.  However, if one tries to have the created JVM (i.e. created by jvm.dll) load a second DLL with C++ callbacks, this fails silently if you try to start the main program via an ant <exec> task.  I am assuming that it can't properly find the 2nd DLL (with the callback code).  No amount of path tweaking has solved this problem to date.

The solution I've used is to encapsulate the program startup into a /bin/tcsh script, which is kicked-off from ant via the <exec> task.  Don't ask me why, but this technique works.  The /bin/tcsh script sets up the path, launches the C++ main program, which creates the JVM via the invocation interface, and is still able to load the 2nd DLL with C++ callback code.

Alan Thompson

P.S.  What do you like about rxvt rather than the basic Cygwin window?


At 03:42 PM 5/28/2003 +0800, Shaddy Baddah wrote:

>Thanks Alan. I have tried this out and it narrows the problem down somewhat.
>It seems to me that my problem is that I am running java from a rxvt and/or
>xterm. I'll bullet some observations:
>
> * I normally enter commands into a bash shell running under a rxvt window.
> * When I ran the sample code from http://www.whitecaps.net/jni/expr.jar
>(here in known as expr code), it worked as expected. This is a strange
>exception that I'll comeback to.
> * Going back to the previous examples I was using, I rebuilt the dll in the
>same way as the build.xml from the expr code does.
> * Not using ant in this instance, I ran the example by entering the java
>command line directly.
> * The error changed in nature, but it was still a no-go.
> * Curiosity aroused, I went back to the expr code, and tried entering in
>the java command line (as per build.xml) into the rxvt and indeed, it failed
>in the same way.
> * I started up a Windows cmd prompt, copied and pasted the command-line,
>and it worked as it did under the ant build.
> * I started up a cmd prompt based Cygwin session, copied and pasted the
>command-line, and it worked as it did under the ant build.
> * Doing the same with my previous example worked as well.
> * Doing the same under Cygwin native xterm, in an xession failed in the
>same was as rxvt.
>
>So, I think it's safe to say, the problem has something to do with the
>terminal the Win32 native java interpreter is running under, and perhaps how
>cygwin handles pseudo-terminals??? But strangely, when run from within an
>ant process as mentioned, it worked ok. I just don't get it.
>
>Regards,
>Shaddy
>
>
>
>----- Original Message -----
>From: "Alan Thompson" <athompson@alphatech.com>
>To: "Shaddy Baddah" <Shaddy_Baddah@hotmail.com>; <cygwin@cygwin.com>
>Sent: Thursday, May 22, 2003 5:54 AM
>Subject: Re: cygwin crashes when loading DLL
>
>
>> Shaddy -
>>
>> I have uploaded some sample code to http://www.whitecaps.net/jni/expr.jar
>.  The expr/jni/hello directory contains a "standard" JNI example (where
>java calls into a C++ program) that works on Cygwin and has an ant buildfile
>(I assume you are using ant.....if not, get it and you'll be happy).  The
>expr/jni/invoke directory has an example using the JNI invocation interface,
>where a C++ program creates a JVM to print "hello".  Output is pasted below.
>>
>> Also, if you haven't seen it, look at the excellent writeup on JNI for
>Cygwin at http://www.inonit.com/cygwin/
>>
>> Alan Thompson
>>
>>
>****************************************************************************
>************************
>>
>> cd expr/jni/hello
>> ant
>>
>> Buildfile: build.xml
>>
>> clean:
>>
>> init:
>>     [mkdir] Created dir: C:\export\expr\jni\hello\bin
>>     [mkdir] Created dir: C:\export\expr\jni\hello\gen
>>
>> javaSrcComp:
>>     [javac] Compiling 2 source files to C:\export\expr\jni\hello\bin
>>
>> ctags:
>>
>> javaComp:
>>
>> javah:
>>      [echo] building *_jni.h...
>>
>> ccComp:
>>     [mkdir] Created dir: C:\export\expr\jni\hello\ctmp
>>      [copy] Copying 2 files to C:\export\expr\jni\hello\ctmp
>>
>>      [echo] Compiler Name:     g++
>>      [echo] Compiler Version:
>>      [exec] g++ (GCC) 3.2 20020927 (prerelease)
>>      [exec] Copyright (C) 2002 Free Software Foundation, Inc.
>>      [exec] This is free software; see the source for copying conditions.
>There is NO
>>      [exec] warranty; not even for MERCHANTABILITY or FITNESS FOR A
>PARTICULAR PURPOSE.
>>
>>
>>      [echo] Compiling for Cygwin...
>>      [echo] Linking for Cygwin...
>>    [delete] Deleting directory C:\export\expr\jni\hello\ctmp
>>
>> build:
>>
>> go:
>>      [java] loading library
>>      [java] calling sayHello
>>      [java] Hello World from C!
>>      [java] trying to get array
>>      [java] answerArrayObj=0x8b74cc
>>      [java] trying to get elem[0]
>>      [java] elem0=0x8b74d0
>>      [java] elemClass=0x8b74d4
>>      [java] valueFieldID=0x22
>>      [java] trying to get valueObj
>>      [java] valueObj=0x8b74d8
>>      [java] trying to get string chars
>>      [java] initial string = 'initial value from java'
>>      [java] trying to set string chars
>>      [java] newJString=0x8b74dc
>>      [java] getting constructor MID
>>      [java] msgCID=0x8bbf18
>>      [java] calling constructor
>>      [java] trying to set string chars
>>      [java] newJString2=0x8b74e4
>>      [java] setting newElem value
>>      [java] trying to set elem[1]
>>      [java] sayHello() returning
>>      [java] sayHello done
>>      [java] answer[ 0 ] = 'Hello World from C!'
>>      [java] answer[ 1 ] = 'the new C string value'
>>      [java] answer[ 2 ] = 'initial value from java'
>>
>> clean:
>>    [delete] Deleting directory C:\export\expr\jni\hello\bin
>>    [delete] Deleting directory C:\export\expr\jni\hello\gen
>>
>> BUILD SUCCESSFUL
>> Total time: 9 seconds
>>
>>
>>
>>
>>
>>
>> cd expr/jni/invoke
>> ant
>>
>> Buildfile: build.xml
>>
>> clean:
>>
>> init:
>>     [mkdir] Created dir: C:\export\expr\jni\invoke\bin
>>
>> javaComp:
>>     [javac] Compiling 1 source file to C:\export\expr\jni\invoke\bin
>>
>> ccCygwin:
>>      [echo] Compiling C++ for Cygwin
>>
>> dlltoolCygwin:
>>
>>
>> ccCompCygwin:
>>
>>      [echo] Compiler Name:     g++
>>      [echo] Compiler Version:
>>      [exec] g++ (GCC) 3.2 20020927 (prerelease)
>>      [exec] Copyright (C) 2002 Free Software Foundation, Inc.
>>      [exec] This is free software; see the source for copying conditions.
>There is NO
>>      [exec] warranty; not even for MERCHANTABILITY or FITNESS FOR A
>PARTICULAR PURPOSE.
>>
>>
>>
>> ccSun:
>>
>> ccComp:
>>
>> build:
>>
>> go:
>>
>> goCygwin:
>>      [exec] <C++> program starting
>>      [exec]   <java> Hello World from C!
>>      [exec] <C++> program terminating
>>
>> goSun:
>>
>> clean:
>>    [delete] Deleting directory C:\export\expr\jni\invoke\bin
>>
>> BUILD SUCCESSFUL
>> Total time: 12 seconds
>>
>>
>> At 02:12 PM 5/20/2003 +0800, Shaddy Baddah wrote:
>>
>> >I am having exactly the same problem trying to build Java JNI's under
>Cygwin
>> >(actually, they are the examples from the 'GNU Win32 related projects'
>> >page ). Robert Bercik, did discover a fix for the problem you
>encountered?
>> >
>> >I have more weirdness to describe. I can run the Java app that loads in
>the
>> >JNI under a regular Windows 2000 'cmd' window and it works fine,
>regardless
>> >of whether there is a cygwin1.dll active or not. But if I try and run the
>> >same Java app from within a cygwin shell, it crashes in the same way.
>There
>> >must be a simple explanation/fix to this one. Help would be greatly
>> >appreciated.
>> >
>> >Thanks in advance,
>> >Shaddy
>>
>>
>>



--
Unsubscribe info:      http://cygwin.com/ml/#unsubscribe-simple
Problem reports:       http://cygwin.com/problems.html
Documentation:         http://cygwin.com/docs.html
FAQ:                   http://cygwin.com/faq/