Hi, Overview Part of JNA API describes as following: 1. Description1: If the native method returns char* and actually allocates memory, a return type of Pointer should be used to avoid leaking the memory. It is then up to you to take the necessary steps to free the allocated memory. 2. Description2: Declare the method as returning a Structure of the appropriate type, then invoke Structure.toArray(int) to convert to an array of initialized structures of the appropriate size. Note that your Structure class must have a no-args constructor, and you are responsible for freeing the returned memory if applicable in whatever way is appropriate for the called function. And the example code shows as following: // Original C code struct Display* get_displays(int* pcount); void free_displays(struct Display* displays); // Equivalent JNA mapping Display get_displays(IntByReference pcount); void free_displays(Display[] displays); ... IntByReference pcount = new IntByReference(); Display d = lib.get_displays(pcount); Display[] displays = (Display[])d.toArray(pcount.getValue()); ... lib.free_displays(displays); That's to say. All the memory allocated by native code must be freed explicitly in JNA part. We must add some free memory methods to support the memory-freeing. Any comments? B.R. Benjamin Wang -----Original Message----- From: Daniel Veillard [mailto:veillard@redhat.com] Sent: 2012年8月20日 14:25 To: Benjamin Wang (gendwang) Cc: stoty(a)tvnet.hu; Daniel.Schwager(a)dtnet.de Subject: Re: Memory free in libvirt JNA On Mon, Aug 20, 2012 at 05:15:45AM +0000, Benjamin Wang (gendwang) wrote: As far as I understat free() is aliased as finalize() on that object so the java runtime will call free() automatically on garbage collection. I'm not a java expert, check some Java litterature for more details about how this is done and the cases where free() might be better called directly. Daniel -- Daniel Veillard | libxml Gnome XML XSLT toolkit http://xmlsoft.org/ daniel(a)veillard.com | Rpmfind RPM search engine http://rpmfind.net/ http://veillard.com/ | virtualization library http://libvirt.org/