Re: Calling conventions (particularly 32-bit ARM)

scott@slp53.sl.home (Scott Lurndal) writes:

Thomas Koenig <tkoenig@netcologne.de> writes:

[...]

What I was criticising was the comittee(s) which made errno handling
for functions like sin() and cos() mandatory, and put activating
it in a globel flag.

>
It's not mandatory.   It's listed as an optional extension, and
even when implemented, it's opt-in at compile time.
>
  "The functionality described is optional. The functionality
   described is mandated by the ISO C standard only for implementations
   that define __STDC_IEC_559__."

I can't find that anywhere in ISO C or POSIX.  What exactly are you
quoting?  ISO C doesn't tie math_errhandling to __STDC_IEC_559__.

There's no requirement in ISO C or POSIX for an implementation to let
users affect the value of math_errhandling, at compile time or
otherwise.  (And POSIX isn't directly relevant; this is all defined by
ISO C.  There might be something in POSIX that goes beyond the ISO C
requirements.)

gcc has "-f[no-]fast-math" and "-f[no-]math-errno" options that can
affect the value of math_errhandling.

A conforming implementation could set math_errhandling to
(MATH_ERRNO|MATH_ERREXCEPT) and not provide a way to change it.

--
Keith Thompson (The_Other_Keith) Keith.S.Thompson+u@gmail.com
void Void(void) { Void(); } /* The recursive call of the void */