Re: memory allocation

[Etienne Gagnon]

Archie Cobbs wrote:
> The only way I could think of would be e.g. allocating memory by creating
> byte[] arrays instead of using malloc(). This seems awkward.

Allocating a byte array and then obtaining a direct pointer to its
elements (or non-moveable copy) using GetByteArrayElements is effectively
the cleanest approach to allocate memory ** through JNI **.  [Note that the
native code must also call ReleaseByteArrayElements to "free" the array.]

Now, the only advantage I see to this approach is that it allows the JVM's 
garbage
collector to free this memory on exit.  Yet, this can also be a problem if
the native code needs to access this memory after calling DestroyVM.

This brings the following question:

What's wrong with using malloc/free in native code, in the first place?

Personally I think that there shouldn't be any problem for native code to
directly call malloc & free.

On the other hand, the GetByteArrayElements/ReleaseByteArrayElements pair should
be used to store pointers to native data in Java objects.  One shouldn't use 
int/long
fields as pointer size is inherently platform dependent (16,16,32,64,128 bits).

Etienne

--
Etienne M. Gagnon, Ph.D.             http://www.info.uqam.ca/~egagnon/
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