[Bug libstdc++/119143] std::cyl_bessel_j incorrect result

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119143

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
     Ever confirmed|0                           |1
   Last reconfirmed|                            |2026-06-05
             Status|UNCONFIRMED                 |NEW

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
I don't know if this is all we need to do:

--- a/libstdc++-v3/include/tr1/bessel_function.tcc
+++ b/libstdc++-v3/include/tr1/bessel_function.tcc
@@ -362,6 +362,12 @@ namespace tr1
     void
     __cyl_bessel_jn_asymp(_Tp __nu, _Tp __x, _Tp & __Jnu, _Tp & __Nnu)
     {
+      if (__builtin_expect(__builtin_isinf(__x), 0))
+       {
+         __Jnu = __Nnu = _Tp(0);
+         return;
+       }
+
       const _Tp __mu = _Tp(4) * __nu * __nu;
       const _Tp __8x = _Tp(8) * __x;