Re: new clang report

Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> On ons, 2011-02-09 at 20:30 +0200, Peter Eisentraut wrote:
>> Regression tests (world):
>>
>> --- src/test/regress/expected/float8.out
>> +++ src/test/regress/results/float8.out
>> @@ -384,7 +384,15 @@
>> SELECT '' AS bad, f.f1 * '1e200' from FLOAT8_TBL f;
>> ERROR: value out of range: overflow
>> SELECT '' AS bad, f.f1 ^ '1e200' from FLOAT8_TBL f;
>> -ERROR: value out of range: overflow
>> + bad | ?column?
>> +-----+----------
>> + | 0
>> + | NaN
>> + | NaN
>> + | NaN
>> + | NaN
>> +(5 rows)
>> +
>> SELECT 0 ^ 0 + 0 ^ 1 + 0 ^ 0.0 + 0 ^ 0.5;
>> ?column?
>> ----------

> So issue here is actually that clang has an option

> -fmath-errno
> Indicate that math functions should be treated as updating errno.

Really? It looks to me like the issue is that pow() is returning NaN
instead of Inf for an out-of-range result. That's a bug: the correct
result is *not* ill-defined, it's simply too large to represent.
If that has anything to do with errno, it's an implementation artifact
that's unrelated to the claimed meaning of the switch.

But I would also note that the Single Unix Spec is unequivocal about
this case:

If the correct value would cause overflow, +-HUGE_VAL is
returned, and errno is set to [ERANGE].

That's "IS set", not "may be set" as in some other cases. So this
behavior should not depend on any such compiler switch anyway, unless
the intent of the switch is "ignore the standard and do whatever we
feel like".

regards, tom lane