Tim Peters <tim.one@comcast.net> writes:
> It's cute: even in C99, an implementation must treat sqrt(negative_number)
> as a domain error. However, under C99 rules:
>
> On a domain error, the function returns an implementation-defined
> value; whether the integer expression errno acquires the value
> EDOM is implementation-defined.
Is that the final text? My copy says
On a domain error, the function returns an
implementation-defined value; if the integer expression
math_errhandling & MATH_ERRNO is nonzero, the integer
expression errno acquires the value EDOM; if the integer
expression math_errhandling & MATH_ERREXCEPT is nonzero, the
``invalid'' floating-point exception is raised.
but it comes from a draft only (99-04). If this is what C99 says, you
actually can tell, in C, whether checking errno will help indicating
the error.
> Do that, and in the end you get a library that still honks off
> IEEE-754 fans anyway (which has its own elaborate and precise rules
> for dealing with fp exceptions).
If the C implementation also implements Annex F, IEEE-754 fans should
be satisfied, no?
Regards,
Martin
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