Bug 1575709

Description of problem:
What problem/issue/behavior are you having trouble with?  What do you expect to see?

We are finding that our application is affected by a bug in the RHEL 7 math library, where errno is not being set for bessel functions such as j0, j1, jn, and also exp2.  In the case of exp2 it IS setting the fe exception – so we can catch that one.  But the j0-n are a problem since the man page documentation on RHEL 6 specifically states they do NOT set the IEEE fe exception for fetestexcept(), but they should be setting errno.

This seems to match this bug report:
https://sourceware.org/bugzilla/show_bug.cgi?id=18611


Version-Release number of selected component (if applicable):

All RHEL 7 flavors running glibc older that 2.23
also all glibc newer than 2.12

How reproducible:

always

Steps to Reproduce:
1. run reproducer in jtest.tar
2.
3.

Actual results:


RHEL 7:

ash-4.2$ ./jtest
Testing J0:
  Before function call, errno = 0, exception query returns 0
  Calling j0( 1e+256 )
  After function call, errno = 0, exception query returns 0
  Returned function value = 2.04732e-131
Testing J1:
  Before function call, errno = 0, exception query returns 0
  Calling j1( 1e+256 )
  After function call, errno = 0, exception query returns 0
  Returned function value = 7.97882e-129
Testing JN:
  Before function call, errno = 0, exception query returns 0
  Calling jn( 1, 1e+24 )
  After function call, errno = 0, exception query returns 0
  Returned function value = -7.83133e-13
Testing EXP2:
  Before function call, errno = 0, exception query returns 0
  Calling exp2( -1222 )
  After function call, errno = 0, exception query returns 16
  Returned function value = 0
bash-4.2$ ldd -r ./jtest
	linux-vdso.so.1 =>  (0x00007ffffb53c000)
	libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f20a521a000)
	libm.so.6 => /lib64/libm.so.6 (0x00007f20a4f18000)
	libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f20a4d01000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f20a493e000)
	/lib64/ld-linux-x86-64.so.2 (0x000055dcbf791000)
bash-4.2$ rpm -qf /lib64/libm.so.6
glibc-2.17-196.el7_4.2.x86_64
[alanm@localhost-live C02014182]$ ./jtest
Testing J0:
  Before function call, errno = 0, exception query returns 0
  Calling j0( 1e+256 )
  After function call, errno = 0, exception query returns 0
  Returned function value = 2.04732e-131
Testing J1:
  Before function call, errno = 0, exception query returns 0
  Calling j1( 1e+256 )
  After function call, errno = 0, exception query returns 0
  Returned function value = 7.97882e-129
Testing JN:
  Before function call, errno = 0, exception query returns 0
  Calling jn( 1, 1e+24 )
  After function call, errno = 0, exception query returns 0
  Returned function value = -7.83133e-13
Testing EXP2:
  Before function call, errno = 0, exception query returns 0
  Calling exp2( -1222 )
  After function call, errno = 34, exception query returns 16
  Returned function value = 0
[alanm@localhost-live C02014182]$ rpm -q glibc
glibc-2.26-24.fc27.x86_64

It has the patch in https://sourceware.org/bugzilla/show_bug.cgi?id=18611 
and it does NOT do the correct thing.

I'm suspecting that the wrapper functions to the __ieee754_jXXX functions need to
be more like the RHEL 6 versions


Expected results:

RHEL 6 glibc provides results which are expected by the user.
[alanm@vmw102 C02014182]$ ./jtest
Testing J0:
  Before function call, errno = 0, exception query returns 0
  Calling j0( 1e+256 )
  After function call, errno = 34, exception query returns 0
  Returned function value = 0
Testing J1:
  Before function call, errno = 0, exception query returns 0
  Calling j1( 1e+256 )
  After function call, errno = 34, exception query returns 0
  Returned function value = 0
Testing JN:
  Before function call, errno = 0, exception query returns 0
  Calling jn( 1, 1e+24 )
  After function call, errno = 34, exception query returns 0
  Returned function value = 0
Testing EXP2:
  Before function call, errno = 0, exception query returns 0
  Calling exp2( -1222 )
  After function call, errno = 34, exception query returns 0
  Returned function value = 0
[alanm@vmw102 C02014182]$ rpm -qf /lib64/libm.so.6
glibc-2.12-1.209.el6_9.2.x86_64

Additional info: