[PD-dev] Memory reallocation problem

[Isidro Gonzalez]

Many thanks for your kind answer.
I´m surprised because the way I use to allocate memory is the most commonly used.
Wouldn´t initializing the pointers to NULL destroy all the contents of previous memory they hold, if any...? So, why to use "realloc" this way, then? I would use "free" and "malloc", instead.
Your advice works fine but when I try to use the memory, the object makes PD to crash.
Any further ideas? 
Many thanks
Isi


--- On Tue, 10/13/09, Justin Glenn Smith <noisesmith at gmail.com> wrote:

> From: Justin Glenn Smith <noisesmith at gmail.com>
> Subject: Re: [PD-dev] Memory reallocation problem
> To: "Isidro Gonzalez" <isidro_gonsoy at yahoo.com>
> Cc: pd-dev at iem.at
> Date: Tuesday, October 13, 2009, 4:10 PM
> Isidro Gonzalez wrote:
> > Hi:
> > I am triying to allocate a n*n matrix of a type
> defined structure of data.
> > The pd external object example I'm sending attached is
> very simple: each time it receives any message except the
> "clear" message it increments a counter and reallocate a
> matrix of n*n members where n is the number stored in the
> counter (so, 1, 4, 9, 16 and so on). If it receives the
> "clear" message, it reset the counter to 1 and reallocate
> the matrix to 1x1.
> > The fact is that the object crashed when reallocating
> and I can't be able to know what am I doing wrong. I use the
> traditional "realloc" function.
> > Any help will be welcome.
> 
> realloc does no initialization of data.
> 
> In the for loop in the dummy_alloc function you are calling
> realloc on
> uninitialized pointers. The fact that this ever fails to
> crash is
> because you are by chance getting NULL pointers from the
> realloc when
> you increase the size of a.
> 
> You need to manually set the newly acquired bytes in a to
> be NULL before
> you can safely call realloc with them as arguments.
>