IKVM drops on subsequent JNI calls

[Дейзи Чейн]

Hi all,
I've run into trouble using JNI calls via IKVM, under very specific circumstances, so, maybe, this info could be helpful to others. I have some native dll that was joined to my old Java app. It worked nice for several years. Under IKVM (I converted a part of my app to make a library for .net port), it craches with "attempt to read/write protected memory" or "ExecutionEngineExeption" (the type of error every time is randomic). Under debugger it usually just closes application silently without any notice.
After some investigation I seem to find the root of the trouble: I guess the native library is loaded/unloaded for every call! At least, it looks like that: the first call to dll initializes some objects inside it (in my case, context of very specific cryptoprovider that isn't WinCSP-compatible). And this works. The subsequent call relies on these initialized objects - and it fails! Any number of calls that don't rely on already initialized objects - work fine. Furthermore, if I just make a new JNI function that "joins" the two calls - it works as needed.
Yes, I used the last two development builds.
For now, I see the only way to remedy the situation - rewrite all this Java code on C# using PInvoke, not IKVM/JNI. So I just wanted to warn others that such problem does exist.

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[Jeroen Frijters]

Hi,

This is not exactly helpful. I can assure you that the native library is not loaded/unloaded for every call.

Have you tried running your code on Sun's Java with the -Xcheck:jni option?

Regards,
Jeroen

> -----Original Message-----
> From: Дейзи Чейн [mailto:daisychain@...]
> Sent: Saturday, September 19, 2009 11:09 AM
> To: ikvm-developers@...
> Subject: [Ikvm-developers] IKVM drops on subsequent JNI calls
>
> Hi all,
> I've run into trouble using JNI calls via IKVM, under very specific
> circumstances, so, maybe, this info could be helpful to others. I have
> some native dll that was joined to my old Java app. It worked nice for
> several years. Under IKVM (I converted a part of my app to make a
> library for .net port), it craches with "attempt to read/write
> protected memory" or "ExecutionEngineExeption" (the type of error every
> time is randomic). Under debugger it usually just closes application
> silently without any notice.
> After some investigation I seem to find the root of the trouble: I
> guess the native library is loaded/unloaded for every call! At least,
> it looks like that: the first call to dll initializes some objects
> inside it (in my case, context of very specific cryptoprovider that
> isn't WinCSP-compatible). And this works. The subsequent call relies on
> these initialized objects - and it fails! Any number of calls that
> don't rely on already initialized objects - work fine. Furthermore, if
> I just make a new JNI function that "joins" the two calls - it works as
> needed.
> Yes, I used the last two development builds.
> For now, I see the only way to remedy the situation - rewrite all this
> Java code on C# using PInvoke, not IKVM/JNI. So I just wanted to warn
> others that such problem does exist.
>
> -----------------------------------------------------------------------
> -------
> Come build with us! The BlackBerry® Developer Conference in SF, CA
> is the only developer event you need to attend this year. Jumpstart
> your
> developing skills, take BlackBerry mobile applications to market and
> stay
> ahead of the curve. Join us from November 9-12, 2009. Register
> now!
> http://p.sf.net/sfu/devconf
> _______________________________________________
> Ikvm-developers mailing list
> Ikvm-developers@...
> https://lists.sourceforge.net/lists/listinfo/ikvm-developers

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