Re: Calling conventions (particularly 32-bit ARM)

Michael S <already5chosen@yahoo.com> writes:

On Tue, 14 Jan 2025 14:22:19 GMT
scott@slp53.sl.home (Scott Lurndal) wrote:

Clearly there are programmers who wish to be able to detect
certain exceptions, and POSIX allows programmers to
select that behavior.

>
Raising of FP exceptions is orthogonal to question of one instruction
vs library call. If anything, when exceptions are enabled, with
single-instruction implementation it is probably easier for exception
handler to find the reason and generate useful diagnostics.

It seems to me that "raise an exception" is in the IEEE 754 sense (by
default set a sticky flag in an internal register), not in the C sense
of raising a signal.  AFAIK you can tell the system to produce a
signal for some exceptions, but the default on Linux is not to.

As to what POSIX allows, on the manual page that you quoted I see no
indication that implementation is required to give to programmer to
select this or that behavior. I read it like implementation is allowed
to make the choice fully by itself.

And if it is friendly, it can give the programmer a compiler option to
select between the variants.

- anton
--
'Anyone trying for "industrial quality" ISA should avoid undefined behavior.'
  Mitch Alsup, <c17fcd89-f024-40e7-a594-88a85ac10d20o@googlegroups.com>