Re: Why couldn't an operating system be written in ada

[Shark8 <onewingedshark@gmail.com>]

On Tuesday, February 26, 2019 at 4:14:03 PM UTC-7, lyttlec wrote:
> On 2/26/19 3:46 AM, Niklas Holsti wrote:
> > On 19-02-25 23:56 , Rabican wrote:
> >> On Saturday, July 13, 1996 at 3:00:00 AM UTC-4, Mark  McKinney wrote:
> >>> It has been claimed that the capability to interface with other
> >>> languages
> >>> is a great asset to ada. Sometimes interfacing can be a tremendous
> >>> liability. Besides the OS could perform most of work that the language
> >>> runtime does. So why not build an OS in ADA?
> >>
> >> yeah why not?  anything?
> > 
> > This has been discussed many times before in comp.lang.ada.
> > 
> > The first question is not "why not build an OS is Ada", the first
> > question is "why build a new OS at all"?
> > 
> > Then, if a new OS is going to be built for some reason, we can ask which
> > language should be used, and of course (IMO) Ada would be a strong
> > contender. However, for larger systems, the OS must usually implement a
> > "process" concept that goes beyond Ada tasking and provides isolation
> > between different users and applications. This means that the OS will
> > have a process/service-level API that is not, as such, Ada-language
> > specific. And so the fact that the OS is implemented in Ada becomes
> > invisible on the application level.
> > 
> > This is not to say that an OS API specified in Ada could not be an
> > improvement (for Ada applications) on the current OS APIs which are
> > usually specified in C. However, such an Ada OS API could also be
> > provided for an OS implemented in C or some other language.
> > 
> > At present, for small, (mostly) stand-alone embedded Ada systems, the
> > bare-machine Ada run-times are sufficient -- and they are usually
> > written in Ada. For larger or network-connected systems, where a
> > comprehensive OS is needed, the Ada compiler vendors often provide
> > run-times that hide the chosen OS (say, VxWorks) from the Ada
> > applications, making the OS implementation language irrelevant (as long
> > as the OS works).
> > 
> > There are of course exceptions, such as the RTEMS real-time OS/kernel
> > which originally supported Ada run-times but for which I believe there
> > is today no vendor-supplier Ada run-time, which means that Ada projects
> > that choose to use RTEMS (for some unfathomable reason) have to bind to
> > the RTEMS C-level services directly.
> > 
> >> can ada do CSP?
> > 
> > Your question is rather vague, but the answer is almost certainly "yes"
> > -- the Ada rendez-vous is very similar to an (unbuffered) Occam channel.
> > 
> As to why write an OS in Ada, read Bruce Schneier's book "Click Here to
> Kill Everybody". There is a need for an OS that can be proven correct
> and can be scaled down to SBC size. Only a small subset of Ada would be
> required to write the kernel. For example, Tasks are not needed to write
> a kernel, nor are any POSIX features.
> As far as I can tell, the only candidate language for writing such an OS
> are Ada and Fortran. (Not too sure about Fortran.)

Tasks would be ideal for a nice chunk OS design, especially considering the move to multicore architectures.