Re: alloca is bad?

[Fernando Nasser <fnasser at cygnus dot com>]

Nick Duffek wrote:
> 
> On 11-Nov-2000, Andrew Cagney wrote:
> 
> >This brings up an additional, possibly relevent, point.  Given the code:
> 
> >       int a[size];
> 
> >vs
> >       int *const a = alloca (size * sizeof (int));
> >or     int *const a = (int *) alloca (size & sizeof (int));
> 
> >(er and there is even one in the above and no it wasn't contrived!) the
> >latter definitely has more potential error points (both when being
> >written and being maintained).  Coding pratices that minimize a
> >programmers error rate should be considered.
> 
> That's one of the strongest arguments in favor of alloca over malloc.  The
> programmer error potential in these two lines of code:
> 
>         int *const a = alloca (size * sizeof (int));
>         int *const a = malloc (size * sizeof (int));
> 
> is exactly the same, but adding free() in the malloc case adds much more
> potential for errors, as demonstrated by the popularity of tools for
> finding memory leaks.  The malloc case gets even more error-prone where we
> need to check for non-local exits and add cleanup chains.
> 

Meomory leak -> small problem, easy to identify the culprit.

Stack corruption -> big problem, difficult to know even where to start.



-- 
Fernando Nasser
Red Hat Canada Ltd.                     E-Mail:  fnasser@redhat.com
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