[CELT-dev] Endless Loop

[Mike Hooper]

Greg,

I have checked and varied my allocations and they appear to be correct. I am
using the TI CCS4 development environment which does not support alloca or
var-arrays. So I am using the application managed pseudo-stack. I have tried
many (oversized) allocations, all of which appear to have the same issue.

What I have determined is that there is a recursive loop in the following
code from which I never return:

"static celt_int16 *get_required_bits_pair(celt_int16 *_bits1,
 celt_int16 *_bits2,celt_int16 *_tmp,int _n1,int _n2,int _maxk,int _frac)"

This function is first called after 15 iterations of:
"celt_int16 **compute_alloc_cache(CELTMode *m, int C)"

Around the 15th iteration the following line is executed which goes into a
recursive loop that eventually exceeds the heap allocation (no matter how
big it is)

 "_tmp=get_required_bits_pair(_bits2,_tmp,_bits1,
       _n1>>1,_n1+1>>1,_maxk,_frac);"

Here are the values of the variables on entry:
_bits1 = 0x00000062
	*(_bits1) = 0
_bits2 = 0x000000E2
_tmp = 0x000067FA
_n1 = 4
_n2 = 4
_maxk = 128
_frac = 4
tmp2 = 0x0008007F

Can you see anything obvious that would cause this to loop indefinitely?

Thx

MikeH

-----Original Message-----
From: Gregory Maxwell [mailto:gmaxwell at gmail.com] 
Sent: Thursday, July 01, 2010 4:05 PM
To: Mike Hooper
Cc: celt-dev at xiph.org
Subject: Re: [CELT-dev] (no subject)

On Thu, Jul 1, 2010 at 3:58 PM, Mike Hooper <mihooper at bellsouth.net> wrote:
> Jean-Mark, Tim,
> Could either of you expound on the following comment in cwrs.c?
>  /*If _k==0, the following do-while loop will overflow the buffer.*/
> ----------------------------------------------------------------
> ...because the following do-loop does overflow the buffer when k=126
>     k=2;
>
>     do _u[k]=(k<<1)-1;
>     while(++k<len);


Have you correctly set the relevant allocation defines for your system?

Are you using C99 var-arrays, alloca, or the application managed
pseudo-stack?