Jakub, sorry about the global variable. The recent work on packet-dtn.[ch] 
comes from me. I read all the wireshark developer info prior to diving in, but 
I admit I don't recall any particular discussion of this. As you can see from 
[1], there were a great many global variables in there prior to my work. I just 
assumed that was the way to do it, and yet I still agonized over how to most 
effectively get the "bundle_custodian" variable into the code. I agree that 
global variables are to be avoided.

Do you have particular suggestions? Are some of the global variables here "less 
offensive" than others?

Jim



Jim Wright
BioServe Space Technologies
[email protected]<mailto:[email protected]>
303-492-1579

On May 8, 2012, at 4:26 PM, Jakub Zawadzki wrote:

Hi,

What's current policy of using global variables in dissectors?
Some time ago I've fixed some issues connected with storing ep_ memory in
global variables: r42002, r42005, r42008 and prepared patch for bug #7060

And I'm *really* not happy when we add it, like recent commit to packet-dtn.c 
[1]
This commit seems safe, but I'd prefer to ban using global variables to store
any information about current dissection.

AFAIK we also plan to have libwireshark thread-safe.
We can use TLS support in glib (GStaticPrivate[2]) or
what compilers offers like __thread in GCC[3] or __declspec(thread) in MSVC[4]
or even mutex for whole protocol dissection
but wouldn't be better to not use global variables?

There's already packet_info structure which is always private for current
dissection. The easiest fix would be to move all global variables
to packet_info structure. Anyone against it?


[1] 
http://anonsvn.wireshark.org/viewvc/trunk/epan/dissectors/packet-dtn.c?r1=42507&r2=42506&pathrev=42507
[2] http://developer.gnome.org/glib/2.30/glib-Threads.html#GStaticPrivate
[3] http://gcc.gnu.org/onlinedocs/gcc-3.3.1/gcc/Thread-Local.html
[4] http://msdn.microsoft.com/en-us/library/6yh4a9k1.aspx
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