Good morning for this side of the world...
My patch compiles against the latest trunk, and as far as can see, it
works, and even as expected. I only have to make the GTK GUI show some
relevant information, because currently it always shows that the
chance for a city to catch a plague is 0.
It seems that, as I have planned, my patch effectively keeps cities
from growing to large without certain improvements, while not setting
a fixed size. A city without an aqueduct is unlikely to grow above
size 8 for long. Haven't got to larger cities yet.
I'll send a newer patch in a couple of days or so, with a ruleset that
uses the new feature.

On 12/18/08, Madeline Book <madeline.b...@gmail.com> wrote:
> On 12/17/08, Yoav Luft <yoav.l...@gmail.com> wrote:
>> Hi,
>> I've written a little patch to the stable tree, as a way to acquaint
>> myself with the code of freeciv.
>> The patch adds the new functionality of plagues to game, which are
>> determined randomly based on the size, pollution, improvements and
>> trade routes of a city.
>> The patch segfaults on me. I get that massage:
>> Program received signal SIGSEGV, Segmentation fault.
>> 0x000000000041bd7d in pay_for_units (pplayer=0x861e18, pcity=0x1890fc0)
>>     at ../utility/speclist.h:110
>> 110       return genlist_size(tthis->list);
>>
>> it only happens when the game.info.plague_on is true, but I do not
>> understand what genlist_size() does, or where and why it is called. It
>> is my first attempt at adding code to freeciv, and I've spent some
>> nights trying to understand what went wrong, but I'm kinda clueless.
>> I guess it's not a bug, but rather a I didn't do something they it
>> should be done, but I could find what that is.
>>
>> Attached is the patch.
>> I will appreciate any help, even in explaining me what genlist_size does.
>
> The function genlist_size returns the size of a "genlist" which is a
> linked list of pointers. Genlists are used to implement speclists,
> which are just macro-generated interfaces to the genlist functions
> for specific data types (to avoid the type unsafe void pointers used
> by genlists). These data structures are defined in utility/genlist.h
> and utility/speclist.h.
>
> The particular segfault you have there is in all likelyhood caused
> by an operation on a NULL list somewhere; it would help if you
> looked at the entire backtrace to see the history of function calls.
> Then when you have a rough idea of where the NULL list might
> be, you can use gdb to step through the code or just insert some
> printfs (:D) to have the program tell you how far it gets before
> crashing. Once you pin point the location of the NULL access you
> can trace back the code path and find what caused the list to
> be NULL in the first place (you would check all the changes you
> made that get activated by your new setting).
>
> There is some information about using gdb for debugging here:
> http://freeciv.wikia.com/wiki/Bug_Reporting
>
> Also, I looked at your patch and it is actually not that bad at first
> glance. Granted you need to setup diff to ignore all those useless
> files that change every configure/make cycle, and setup your
> editor to follow the freeciv coding style more closely. Of course
> this is only if you intend to submit your patch for inclusion later.
>
> Here are some more helpful pages:
> http://freeciv.wikia.com/wiki/How_to_Contribute
> http://freeciv.wikia.com/wiki/Coding_Style
>
> Oh and by the way, you should implement new features on the
> trunk branch; the "stable" 2.1.x series is only getting bugfixes
> now.
>
> -----------------------------------------------------------------------
> 黒死病で死にたくない。
>
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