[PATCH, PR] Crash of Bessel functions at x==0!

[Paolo Carlini]

Hi,

On 02/07/2013 04:34 AM, Ed Smith-Rowland wrote:
> All,
>
> This patch catches cyl_bessel_i, and cyl_bessel_j returning -nan for 
> zero argument.  Not sure how i missed that.
>
> Anyhow, this patch cleans that up.
> Also, spurious const is removed from numeric arguments of internal 
> functions throughout the TR1 special maths.
These two hunks look straightforward and can certainly go in now. Thanks.
> Also, a better asymptotic treatment of Bessel functions is supplied.
This one worries me a bit: we don't want to introduce regressions on 
some less known platform at this stage. Can we delay it to post 4.8.0? 
4.8.1 would be also fine.

By the way, in general, in __cyl_bessel_jn_asymp and in other places, 
something like an hardcoded 1000, without a comment, without a specific 
analysis explaing why 1000 instead of 100 or 10000 is something we 
should really, really, really, avoid. At minimum, if we can't do better 
in terms of analyzing the behavior of each specific algorithm, those 
constants should be given a name (likely bundled together in sets), be 
documented in the docs to enable the users to change the values away 
from the defaults.

In any case, please remove the "// { dg-do compile }" from the testcase: 
we want to *run* it (the default behavior), right? Also, please try to 
follow the common format, have a separate function with the tests, 
called by main, definining a test variable, etc, etc.

Thanks!
Paolo.