[Cryptography] tail recursion in C [was Re: "NSA-linked Cisco exploit poses bigger threat than previously thought"]

[Ron Garret]

On Aug 28, 2016, at 12:40 PM, Tom Mitchell <mitch at niftyegg.com> wrote:

> On Sun, Aug 28, 2016 at 12:16 AM, Ron Garret <ron at flownet.com> wrote:
> On Aug 27, 2016, at 7:16 AM, Howard Chu <hyc at symas.com> wrote:
> 
> > Ron Garret wrote:
> >> All of these are reasons why I dispute the claim that C is “a good portable assembler.”
>  
> > We live in a world of finite resources. We are all always operating under very tight resource constraints. Wasting cycles or bytes is not doing anyone any favors.
> 
> You can’t be serious.  Remember, we’re not talking about the efficiency of the compiled code here, we’re talking about the efficiency of the *compiler*.  Arguing that we should use unsafe languages in order to conserve electricity is just ridiculous.
> 
> I once thought that modern processors would remove a lot of the frugal 
> habits of many old timers (Clearly emacs is not frugal.).  The resources of
> a Raspberry Pi are luxurious... 
> 
> However the IOT is emerging on some rather sparse resources
> and those tool chains and programmers are wrestling with the old
> fast vs space battles.  Stacks so small that recursion of any kind 
> is a big risk and should be recast as looping structures.  And no operating
> system...
>  
> For this and other reasons C is not going away quickly and the freedom
> and ambiguous bits of C make optimization near impossible.
> Instruction sets are growing in complexity so quality hand coding 
> has become very uncommon and a "portable" assembler is still
> needed.

The first half of my career I worked on autonomous mobile robots.  Back in those days (late 80’s, early 90’s) we didn’t have Raspberry Pi’s, we had 8-bit processors with typically 16k of flash and 1-2k of RAM.  If we were lucky we had a 68020 with 8MB of RAM.  We programmed those systems in Common Lisp.  On the 68020 systems we ran Lisp directly, and on the 8-bit processors we wrote code in Forth and in DSL’s whose compilers were written in CL because writing a compiler in CL was (and still is) really easy.

Yes, a portable assembler is a very handy thing.  But C is not the only option.

rg

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