fxtv@litp.UUCP (04/08/87)
I am trying tu use the exception mechanism available in VAX11 assembly language under 4.3BSD. My first attempt is not really successful... I have read both "the Intrduction to VAX-11 Architecture and assembly language" and "the VAx-11 Architecture Reference Manual". In fact I never have the impression that my handlers are taken into account. Is is possible to get any informations about this problem? Thanks in advance. [fxtv] UUCP: ..!decvax!mcvax!inria!litp!fxtv
ok@quintus (09/14/88)
There is a dispute going on in comp.lang.fortran which comp.arch readers may be able to contribute to. I have been arguing that some sort of limited exception handling facility should be _standard_ in Fortran. (Several Fortran processors already have some way of suppressing/counting/handling exceptions. The trouble is that they don't have the _same_ way.) What I have in mind is something vaguely ADA-ish, except that while a processor would be allowed to refuse to handle an exception, it would be obliged to provide this information at run-time. I have in mind something like HANDLE (exception name string expression) IN statements to be protected CANNOT HANDLE statements to use if protection unavailable HANDLER statements to recover END HANDLE Note that *precise* exceptions are not required. There has to be some way of ensuring that any pending exceptions are delivered when the end of the protected block is reached. In fact, no exception support is required, as a Fortran processor would be entitled to generate code for the "CANNOT HANDLE" case alone. J Giles of Los Alamos has been arguing that such a feature would not be "universally portable" and would impose a significant performance burden on some machines. I don't see the problem, and suspect that this is because the architectures I know about are supermicros and older mainframes, not supercomputers or signal-processors. On which machines would it be excessively expensive (a) to detect exceptions, or (b) to report them to user code rather than killing the process? Does anyone know of machines which have an ADA implementation where numeric_error exceptions aren't/can't be handled?