Re: Ada and QNX

[dvdeug@x8b4e516e.dhcp.okstate.edu (David Starner)]

On Mon, 16 Oct 2000 11:09:30 -0500, Igor Kovalenko wrote:
>Perhaps my personal doubts aren't that personal, huh? Nobody appears to
>write an OS in Ada, being so good for system level work. 

Tradition; what the programmers know; popularity; compiler availability - 
all reasons why OSs are implemented in the langauges they are. 

>And by the way,
>many people say that GCC does not generate good code for C, so I'm kinda
>curious how does GNAT manage to generate good code for such a more
>complex language as Ada. 

GCC produces pretty good code. It's not best, but it's not bad code either.
Ada's range constraints can often help the compile produce better code than
a language without range constraints?

As for Ada compilers, I remember a Dr. Dobbs article a few years back,
an interview with Prof. Kahan, who pointed out that the only compiler
to take full advantage of the ix87 stack was one specific Ada compiler.
Like all other compilers, Ada compilers range from the good to the bad.

>Aside from code generation itself, how do they
>manage to implement things like rendesvous in an efficient AND portable
>way? Such things normally belong to system-dependent runtime libraries,
>but in Ada they are part of language and having no proof I nevertheless
>suspect that they are implemented by trading efficiency for portability.

Why would you suspect that? What justifaction would you have to assume that?
It's just like C - you can implement the C library in a portable way, or
an efficent way, and it varies, but most good C implementations are done
the efficent way. Same with Ada.

-- 
David Starner - dstarner98@aasaa.ofe.org
http://dvdeug.dhis.org
If you wish to strive for peace of soul then believe; 
if you wish to be a devotee of truth, then inquire.
   -- Friedrich Nietzsche