Re: DrawContext -- reports on self?

On Sun, Aug 28, 2011 at 11:24:27PM -0500, Bob Friesenhahn wrote:
> On Mon, 29 Aug 2011, [email protected] wrote:
>> Hrmm... so I should:
>>
>> DrawContext *dc;
>> dc=DrawAllocateContext(); /* like this? */
>
> No, because DrawContext is already a pointer.
>
>> I was having a tough time w/ leaks and core dumps w/ my various attempts... am currently:
>>
>> DrawContext dc;
>> dc=DrawAllocateContext(); /* this is leak-free, crash-free */
>
> Looks better.
>
>> but my tests: if(!dc) { // no draw context... } were not working like I expected.
>
> It seems like that should work.  However, if the DrawContext is not  
> immediately allocated via DrawAllocateContext(), then it is safest to  
> allocate it like
>
> DrawContext dc = (DrawContext) NULL;
>
> so it has a known initial value.  Also, if you destroy and re-use the  
> same context, then it could have a pointer value for the previously  
> destroyed context since DrawDestroyContext() does not change the passed 
> pointer value.

^--- this might have been what stung me. I'll work with what you've
described here; I was initializing to NULL until I had an image
(otherwise fails w/ assert()), but was probably expecting more w/
the Destroy()... and was a bit confused by it's pointerness, but not
stored in a pointer. I saw the MagickMalloc() (might be wrongname)
and freeing... but didn't fully understand how to treat the handle.

Thanks for the reply :)

-bch

> A complex example (which is part of the test suite) may be seen in  
> Mercurial at
>
> http://graphicsmagick.hg.sourceforge.net/hgweb/graphicsmagick/graphicsmagick/file/775816effda4/tests/drawtest.c
>
> This one does not have leaks or crash.
>
> Bob
> -- 
> Bob Friesenhahn
> [email protected], http://www.simplesystems.org/users/bfriesen/
> GraphicsMagick Maintainer,    http://www.GraphicsMagick.org/

-- 
Brad Harder
Method Logic Digital Consulting
http://methodlogic.net/
http://twitter.com/bcharder


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