[Xenomai-help] native heap services and overloading new

[Xenomai-help] native heap services and overloading new

[Brandt Erickson]

I have some code where I'd like to be able to dynamically allocate memory
in realtime.  Since the code is written in C++, I was thinking of just
making a huge global RT_HEAP and overloading the new and delete operators
to use the rt_heap_alloc and rt_heap_free functions.  First off, I'm
wondering if there are any caveats to this sort of thing that wouldn't be
obvious to someone new to xenomai like myself.  Second, if I fail to call
rt_heap_delete before the program terminates, does the heap remain
registered hang potentially causing problems when I try to re-allocate the
heap when the program is run again?  Thanks.
-Brandt

Re: [Xenomai-help] native heap services and overloading new

[Jan Kiszka]

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Brandt Erickson wrote:
> I have some code where I'd like to be able to dynamically allocate memory
> in realtime.  Since the code is written in C++, I was thinking of just
> making a huge global RT_HEAP and overloading the new and delete operators
> to use the rt_heap_alloc and rt_heap_free functions.  First off, I'm
> wondering if there are any caveats to this sort of thing that wouldn't be
> obvious to someone new to xenomai like myself.  Second, if I fail to call
> rt_heap_delete before the program terminates, does the heap remain
> registered hang potentially causing problems when I try to re-allocate the
> heap when the program is run again?  Thanks.

For now: yes, the heap will stay, no automatic cleanup (the posix skin
already have this). You could then run into naming conflicts and you
lose memory, of course.

But you could install some signal handler for cleaning up. We do so in
our native-skin-based framework (also C++, but no "evil" ;) features in
use). We even catch SIGSEGV this way.

Jan


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Re: [Xenomai-help] native heap services and overloading new

[Philippe Gerum]

On Wed, 2006-08-02 at 21:09 +0200, Jan Kiszka wrote:
> Brandt Erickson wrote:
> > I have some code where I'd like to be able to dynamically allocate memory
> > in realtime.  Since the code is written in C++, I was thinking of just
> > making a huge global RT_HEAP and overloading the new and delete operators
> > to use the rt_heap_alloc and rt_heap_free functions.  First off, I'm
> > wondering if there are any caveats to this sort of thing that wouldn't be
> > obvious to someone new to xenomai like myself.  Second, if I fail to call
> > rt_heap_delete before the program terminates, does the heap remain
> > registered hang potentially causing problems when I try to re-allocate the
> > heap when the program is run again?  Thanks.
> 
> For now: yes, the heap will stay, no automatic cleanup (the posix skin
> already have this). You could then run into naming conflicts and you
> lose memory, of course.
> 
> But you could install some signal handler for cleaning up. We do so in
> our native-skin-based framework (also C++, but no "evil" ;) features in
> use). We even catch SIGSEGV this way.
> 

Another simple option: the binding operation is particularly useful for
recycling/discarding lingering objects.

RT_HEAP app_heap;

void init_heap (void)
{
	RT_HEAP old_heap;

	if (rt_heap_bind(&old_heap, "foo", TM_NONBLOCK) == 0)
		rt_heap_delete(&old_heap);

	rt_heap_create(&app_heap, "foo", ...);
}

-- 
Philippe.