Re: Ada "library only" compiler ?

[Niklas Holsti <niklas.holsti@tidorum.invalid>]

On 12-07-21 02:22 , Dennis Lee Bieber wrote:
> On Sat, 21 Jul 2012 00:11:18 +0300, Niklas Holsti
> <niklas.holsti@tidorum.invalid> declaimed the following in
> comp.lang.ada:
>
>> On 12-07-20 23:05 , Patrick wrote:
>
> 	<snips>
>
>> But there is at least one Ada compiler (AdaMagic) that can compile Ada
>> source to C source, using C as the target language, instead of compiling
>> to machine code. Through this compiler, Ada is available on most devices.
>>
> 	As I recall, that is also how the first qualified Ada compiler
> worked -- the NYU/AdaEd translator converted Ada to C source code.

My understanding is that the first version of Ada/Ed was an interpreter 
written in the SETL language, and a later version was an interpreter 
written in C, but not a translator to C. See 
http://www2.informatik.uni-stuttgart.de/iste/ps/AdaBasis/pal_1195/ada/userdocs/html/cardcat/adaed.html.

Perhaps the C implementation of Ada/Ed is close to what the OP, Patrick, 
has in mind: a C program (that could be presented as a library) that can 
execute Ada programs.

>>> I really hope it will be easier one day to write
>>> full implementation Ada embedded code for a larger number of devices
>>> then it is now.
>>
>> A direct Ada-to-assembler compiler is not the easier way, IMO. And an
>> Ada interpreter, even if you could write one, would be too large for
>> many devices, and too slow for many applications.
>
> 	The main hang-up would be creating some sort of transportable Ada
> run-time to handle the core I/O devices and tasking system. At the
> minimum, you (all of you) are talking the equivalent of a portable BIOS
> system (and look how rapidly M$ operating systems had to find ways to
> bypass said "common" BIOS).

It is well known how to make semi-portable tasking systems -- look at 
all the RT kernels that support multiple processors. For Ada, the Open 
Ravenscar Kernel ORK should be a good point to start from.

IMO there is no well-defined set of "core I/O devices" for embedded 
systems and other kinds of "devices" such as handsets. Ok, most systems 
that interact with the user have some kind of text I/O that could be 
provided as Ada.Text_IO, but some have nothing else; some have only 
volatile memory, while some have non-volatile storage with files and 
directories, etc. I don't see a need for a BIOS, portable or not; 
rather, each device would have its own set of I/O packages. I think that 
is the case for GNAT on Lego Mindstorms.

If we are talking about a portable Ada interpreter (I'm not sure that we 
are), it could perhaps link dynamically to the device-specific I/O 
packages, as plug-ins.

-- 
Niklas Holsti
Tidorum Ltd
niklas holsti tidorum fi
       .      @       .