[sheepdog] [PATCH 1/9] add forward error correction for erasure code

[MORITA Kazutaka]

At Fri, 20 Sep 2013 17:11:34 +0900,
Hitoshi Mitake wrote:
> 
> 
> This would be a great contribution!
> 
> I'd like to post some trivial comments not related to essential part
> of erasure coding.
> 
> At Thu, 19 Sep 2013 18:42:45 +0800,
> Liu Yuan wrote:
> > +#include <stddef.h>
> > +#include <stdint.h>
> > +
> > +#ifdef __GNUC__
> > +#ifndef alloca
> > +#define alloca(x) __builtin_alloca(x)
> > +#endif
> > +#else
> > +#include <alloca.h>
> > +#endif
> 
> This alloca() is only used by fec_decode() in lib/fec.c. The caller
> part,
> 	uint8_t *m_dec = (uint8_t *)alloca(code->k * code->k);
> can be replaced by this because we are using C99 style:
> 	uint8_t m_dec[code->k * code->k];
> 
> Let's eliminate the alloca() definition.

I don't like a variable length array, either.  Those have a risk of
stack overflow.

Can we limit the max size of the array?  Then we can replace it with like

  uint8_t m_dec[MAX_DECODE_BUF];

Or, please add at least assert() to detect too big memory allocation.

Thanks,

Kazutaka