initialization of XXX_COOKIE in C source files

Barry Smith bsmith at
Sat May 10 19:49:34 CDT 2008

On May 10, 2008, at 6:08 PM, Lisandro Dalcin wrote:

> I've noticed that in 2.3.3 all PETSc cookies are initialized to zero
> in sources, but in DEV they are not initialized. What's the reason of
                                     You are quick, I just pushed the  
change last night.

     The reason why they where all initialized to zero was because
- a very long time ago all the cookies where hardwired numbers that we
    chose for each new class
- then we added the ability to request a cookie, but still support the  
   hardwired version. Passing in a pointer to a zero value meant you  
   requesting one, passing in a pointer to a nonzero one meant that  
the cookie
   had a hardwired value.
- over time all the hardwired ones were unhardwired, but the convention
   of initializing them to zero before hand was never changed.

   There was some convoluted logic for why the PetscEvent values were
all initialized to zero also. When fixing up the events I also fixed  
the cookies
The reason is Barry's rule # 54, "nothing should be done in a code  
a reason, otherwise it will be confusing to others looking at the  
code." For example,
even now, whenever anybody made some new events they initialized them
to zero, why? Not because they need to be, but simply because they  
were in
code the developer copied from.

  Were you taking advantage of their initialization to zero? If so,  
rather than depending
on each cookie being initialized to zero I would suggest handling this  
of "check if initialized" stuff at a package by package level or  
library by library level.
Please let me know what you need.


> this change?
> -- 
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> Tel/Fax: +54-(0)342-451.1594

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