lib/46434: tests/lib/libm/t_cosh should not depends on exp()

[isaki%NetBSD.org@localhost]

>Number:         46434
>Category:       lib
>Synopsis:       tests/lib/libm/t_cosh should not depends on exp()
>Confidential:   no
>Severity:       non-critical
>Priority:       medium
>Responsible:    lib-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Wed May 09 03:10:00 +0000 2012
>Originator:     Tetsuya Isaki
>Release:        NetBSD 6.0_BETA/x68k
>Organization:
NetBSD
>Environment:
>Description:
The 'cosh_def' test in tests/lib/libm/t_cosh.c (rev 1.4) uses
the following formula:
  cosh(x) = (exp(x) + exp(-x)) / 2

By this method, if exp() is not right though cosh() is right,
the test of cosh() fails.  It's not appropriate.

# By the way, in incomplete m68k FPE (in-kernel FPU emulation),
# cosh() is implemeted (of course, correctly I think :-) but
# exp() is not implemented yet. Therefore, the current test of
# cosh() does not pass X-(

The following tests have a similar problem as far as I found:
 - coshf_def
 - sinh_def 
 - sinhf_def

>How-To-Repeat:
See the source code.
or run the t_cosh test on m68k without FPU.
>Fix:
N/A, Sorry.