Using forking cygwin programmes with JNI

[GALLWEY Martin <Martin_GALLWEY at rta dot nsw dot gov dot au>]

Hi there,

I've got a Java programme which needs to read and write to the stdin and
stdout of a native programme. On Linux, I've used /dev/ptmx and then forked
and exec'd to give myself a single file descriptor which I can use to both
read and write to the child process. I would like to do the same on Windows
with Cygwin, but fork fails with the error message 'Fork failed because of
Resource temporarily unavailable' when called via JNI. The same code called
outside of the JVM works fine. On Linux it works both inside and outside the
JVM.

I've attached a simple programme to demonstrate this. If you follow these
steps, you can re-produce the problem:

gcc -shared HelloWorld.c -o hello.dll
javac HelloWorld.java
java HelloWorld

For me, using Cygwin 1.3.22-1 and Sun's JDK version 1.4.1_03-b02, I get the
following output:

C:\CYGWIN\HOME\ADMINI~1\JNI>java HelloWorld
Usage: java [-options] class [args...]
           (to execute a class)
   or  java -jar [-options] jarfile [args...]
           (to execute a jar file)

where options include:

<snipped several Java options>

    -dsa | -disablesystemassertions
                  disable system assertions
    101 [main] ? 2044 sync_with_child: child 1420(0x3F4) died before
initialization with status code 0x1
    436 [main] ? 2044 sync_with_child: *** child state waiting for longjmp
Fork failed because of Resource temporarily unavailable

I've tried various methods of working around this problem using windows'
'CreateProcess' API method and lots of other stuff, but nothing works as
well as pseudo terminal/fork/exec does on Linux. Has anyone got any
suggestions?

Thank you,

Martin


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Attachment: HelloWorld.c
Description: Binary data

Attachment: HelloWorld.h
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Attachment: HelloWorld.java
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