Hi Pascal, Thanks for the quick feedback. My intention is to reallocate the memory each time I load a new file.
I have a structure called preferences that holds all of the parsed preference values. Just after allocation the pointer to the allocated area is as per sub_packet in this screenshot: [cid:image003.jpg@01D20F7D.BB3C1010] Note that tsumenabled (a gboolean) is TRUE. When I enter the dissector for the first time the pointer is still good: [cid:image004.jpg@01D20F7D.BB3C1010] tsumenabled is still TRUE. But when code that updates a value in the sub_packet array is executed I get this: [cid:image005.jpg@01D20F7D.BB3C1010] Note how tsumenabled has been zapped to FALSE. I reckon my memory allocation has been freed somewhere. Doing a search across the entire solution in Visual Studio I can’t help noticing that there are no other uses of wmem_alloc(wmem_file_scope(), ….) which is a bit worrying. I’ll redesign the code to use the epan scope and try that. Best regards…Paul From: wireshark-dev-boun...@wireshark.org [mailto:wireshark-dev-boun...@wireshark.org] On Behalf Of Pascal Quantin Sent: 15 September 2016 17:49 To: Developer support list for Wireshark <wireshark-dev@wireshark.org> Subject: Re: [Wireshark-dev] I need wmem_alloc advice please Hi Paul, 2016-09-15 18:44 GMT+02:00 Paul Offord <paul.off...@advance7.com<mailto:paul.off...@advance7.com>>: My porting of TRANSUM from LUA to C continues. I now have a working dissector but I then read README.developer and noted the guidance regarding use of static buffers. I assume this applies to arrays too and so I’m now trying to convert the statically defined arrays to versions based on dynamic memory allocation. I’ve converted some string buffers and a simple gboolean array without problems. I then tried to convert an array of structures and this caused crashes all over the place. Before the conversion I had this as a global variable: PKT_INFO sub_packet[MAX_SUBPKTS_PER_PACKET]; I replaced this with a global variable: PKT_INFO *sub_packet; And this in my init function: sub_packet = (PKT_INFO *)wmem_alloc(wmem_file_scope(), (MAX_SUBPKTS_PER_PACKET * sizeof(PKT_INFO))); I subsequently use it like this: sub_packet[i].frame_number = 0; I seem to be getting memory corruption as a result of this change. Weird things happen, like I lose preference variables. What am I doing wrong here? File scope memory is automatically freed each time a preference is changed, or a file is reloaded. If you need to keep some things persistent during all Wireshark instance, consider using epan scope memory for those variables instead. Regards, Pascal. ______________________________________________________________________ This message contains confidential information and is intended only for the individual named. If you are not the named addressee you should not disseminate, distribute or copy this e-mail. Please notify the sender immediately by e-mail if you have received this e-mail by mistake and delete this e-mail from your system. Any views or opinions expressed are solely those of the author and do not necessarily represent those of Advance Seven Ltd. E-mail transmission cannot be guaranteed to be secure or error-free as information could be intercepted, corrupted, lost, destroyed, arrive late or incomplete, or contain viruses. The sender therefore does not accept liability for any errors or omissions in the contents of this message, which arise as a result of e-mail transmission. Advance Seven Ltd. Registered in England & Wales numbered 2373877 at Endeavour House, Coopers End Lane, Stansted, Essex CM24 1SJ ______________________________________________________________________ This email has been scanned by the Symantec Email Security.cloud service. For more information please visit http://www.symanteccloud.com ______________________________________________________________________
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