Detecting when heap is near exhaustion or exhausted?

[OUTWATER]

All - 

Forgot to ask on previous post:  

Does RTEMS panic when the heap runs out?  If not, is there some whay to perform a 
runtime check to determine if the heap is near exhaustion?

Thanks,
keith


> 
> All-
> 
> The GDB command 
> 
> p *((Region_Control *)_Region_Information->local_table[1])->Memory->first
> 
> was shown in the  RTEMS Frequently Asked Questions Manual as a way to determine the 
> amount of heap remaining.
> 
> I'm debugging an application and I start with this much heap:
> $1 = {back_flag = 0x8d, front_flag = 0x40c, next = 0x3c6514, previous = 0x17bdf4} 
> using the command in the FAQ.
> 
> But doing this: 
> p *((Region_Control *)_Region_Information->local_table[1])->Memory->last
> 
> returns 
> $2 = {back_flag = 0x1, front_flag = 0x23bdf8, next = 0x17bdf8, previous = 0x3cd798}
> which seems more like what I expect.
> 
> When I run my application (tclsh), it crashes with this backtrace snippet:
> #0  0x400 in _uhoh ()
> #1  0x20100017 in ?? ()
> #2  0x96f80 in _API_extensions_Run_postswitch ()
>     at ../../../../../../../rtems-4.5.0-beta3/c/src/exec/score/src/apiext.c:100
> #3  0x8e7ee in _Thread_Dispatch () at 
> ../../../../../../../rtems-4.5.0-beta3/c/src/exec/score/src/threaddispatch.c:126
> #4  0x84776 in _Thread_Enable_dispatch () at 
> ../../../../../../gen68360/lib/include/rtems/score/thread.inl:199
> #5  0x84696 in rtems_region_get_segment (id=604045313, size=8, option_set=1, 
> timeout=0, segment=0x177548)
>     at 
> ../../../../../../../rtems-4.5.0-beta3/c/src/exec/rtems/src/regiongetsegment.c:84
> #6  0x7ef88 in malloc (size=8) at 
> ../../../../../../rtems-4.5.0-beta3/c/src/lib/libc/malloc.c:160
> #7  0x6fcfa in TclpAlloc (nbytes=8) at ./../generic/tclAlloc.c:671
> #8  0x1793a in Tcl_Alloc (size=8) at ./../generic/tclCkalloc.c:813
> 
> 
> It seems that malloc is involved, so I try to get the heap size with:
>  p *((Region_Control *)_Region_Information->local_table[1])->Memory->last
>  
> and get:
>   $4 = {back_flag = 1, front_flag = 2313828, next = 0x17bdf8, previous = 0x3b8f7c}
>   
> Looks like there is still plenty of heap.
> 
> Can anyone point out any flaws or errors in my thinking?
> 
> Thanks!
> 
> Keith
>  
>  
> 
>