Re: I need wmem_alloc advice please

[Pascal Quantin <pascal.quantin () gmail com>]

Hi Paul,

2016-09-15 18:44 GMT+02:00 Paul Offord <Paul.Offord () 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.

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