Re: DrawContext -- reports on self?

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.

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/

------------------------------------------------------------------------------
EMC VNX: the world's simplest storage, starting under $10K
The only unified storage solution that offers unified management 
Up to 160% more powerful than alternatives and 25% more efficient. 
Guaranteed. http://p.sf.net/sfu/emc-vnx-dev2dev