Re: Does GNAT support a thread-free RTS?

[Ludovic Brenta <ludovic@ludovic-brenta.org>]

anon wrote on comp.lang.ada:
> Reference: GCC.GNU.org and Adacore.com
>
> My point is. Since "Glade" was put out to pasture, there is no package
> that fulfil the requirement for Annex D, that is stated for the "FSU
> threads" RTL. Because, "PolyOrb" does not meet the "completely accurate
> implementation of Annex D." requirement for "FSU threads".
>
> Plus, between 2004 .. 2010 for Linux (binary package) from
> Libre.Adacore.com only contains native, siji, and maRTE libraries
> only. No default FSU or ZCX RTL. If still available you will have
> to download source and compile your own version to get FSU threads.

Presumably, by "siji" you meant "sjlj" which stands for "setjump/
longjump exception handling".  GCC presently comes with two run-time
systems:

- zero-cost exception handling aka ZCX aka "native", which is the
default
  on most architectures.  The phrase "zero-cost" really means "zero
  distributed cost" which means you do not pay a performance penalty
unless
  and until you raise an exception.  Raising an exception is however
costly.

- sjlj aka setjump/longjump, which is the alternative, in which every
frame
  that might possibly raise an exception calls setjmp(3), thus
incurring
  distributed cost, and raising an exception calls longjmp(3), which
is
  cheap compared to the raising of an exception with ZCX.  sjlj is the
only
  supported run-time system on a few, non-mainstream architectures.

Both run-time systems now use native threads and both support Annex D
(real-time systems) insofar as the underlying kernel does.  The old
FSU threads were intended to provide better support for Annex D but
that was rendered unnecessary by the advances in Linux, Solaris and
other kernels.

It is true that, a few years ago, Glade used to require the sjlj run-
time system to implement exception handling across partitions in in
distributed programs (Annex E).  I know because I packaged it for
Debian.  However, PolyORB has not required sjlj since it introduced
support for Annex E in version 2.2.

--
Ludovic Brenta.
The stakeholders enable the educated core business by leveraging the
plannings.