Re: Runtime startup code for the GNAT Runtime...and a bit of humble pie.

[Brian Drummond <brian@shapes.demon.co.uk>]

On Tue, 19 Mar 2013 12:51:12 +0000, Simon Clubley wrote:

> On 2013-03-19, Brian Drummond <brian@shapes.demon.co.uk> wrote:
>>
>> There was an email just today on gcc-help@gnu.org with part of the
>> picture - in the thread entitled "Controlling ld and as with backend"
>> on how to configure the start.s and end.s subroutines, using the
>> "config/t-
>><target>" files.
>>
>> My own view is that for a minimal Ada RTS, they should do as little as
>> possible unlike the crt.o stuff and that the standard packages'
>> initialisation parts should add whatever is necessary for their
>> inclusion.
>>
>> But this is only a view; I am just beginning down this path (with the
>> TI MSP430 processor, see msp430ada on sourceforge) where the C startup
>> does a lot with e.g. the watchdog timer that is unnecessary if the Ada
>> application decides to turn it off...
>>
>> So I am interested in other views and good documents, should you find
>> any!
>>
>>
> I would like to offer one take on this which has not been mentioned yet
> and that is the issue of reliability of the resulting system as a whole.
> 
> One of the reasons to use Ada over, say C, is for the increased
> reliability of the code. However, what if the ported Ada RTS actually
> results in more unreliable code because of issues the person porting the
> RTS did not fully understand or was simply was not aware of ?

There's a germ of truth in this in that many more man-hours have already 
been spent polishing up C library functions and (in some environments) RTS 
- re-using that where it exists can save time and avoid traps.

But I don't think you're arguing that - if you had to write some bare 
metal stuff of your own - C would be a better language for the job. On 
the contrary, where you have to start from scratch, Ada gives you much 
better tools.

So C comes into play NOT for bare metal programming, but to avoid it 
where you can re-use someone else's effort. Right?

- Brian