Debugging a plugin

David T. Lewis lewis at mail.msen.com
Wed Feb 1 01:54:22 UTC 2006


On Tue, Jan 31, 2006 at 10:25:04PM -0000, Cowdery, Bob [UK] wrote:
> Hi
> 
> Can anyone enlighten me on the best approach to debug a plugin under
> Windows. The code essentially works in its native form but as a plugin
> doesn't do what it should, but doesn't crash or throw exceptions either.
> I would settle for getting hold of stdout/stderr but I can't get
> OSProcess to hook these and I read it doesn't yet support hooking the
> standard streams in Windows. I am using Dev-C++ to build the plugin and
> have tried pointing that at Squeak but it won't play. 

I definitely don't know the best approach so hopefully someone will
give you better answers, but in the mean time...

A crude but effective way is to manually put printf() in the generated
plugin, followed by (don't forget this) fflush(stdout). Ugly but it
works. On Unix, you can just run the VM under gdb and put breakpoints
in your plugin methods, works fine. This may also work on Windows with
Cygwin, although I have not tried it.

I don't know that it will help with debugging plugins, but I'm attaching
a compiled OSProcess plugin (version 4.0) for Windows that may work for
you. I don't know how portable Windows dll's are, but I compiled this
on a fairly recent W2k box, so hopefully it is usable. This allows you
do to for example:

"Open a console window with stdin, stdout, and stderr streams attached."
OSProcess thisOSProcess openConsole.

"Write to the standard output stream, displayed on the console"
OSProcess thisOSProcess stdOut
  nextPutAll: 'this is the standard output stream';
  nextPut: Character lf.

"Handy debugging messages for Smalltalk process debugging"
OSProcess debugMessage: 'hello world'.
OSProcess trace.
OSProcess trace: 'hello world'.

"Close the console window"
OSProcess thisOSProcess closeConsole.


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