[Octave-bug-tracker] [bug #45507] acos returns different results on big input values on gcc 4.8

[Mike Miller]

Follow-up Comment #45, bug #45507 (project octave):

I would start by going back to basics and making sure what we're seeing with
Octave is reflective of the system libraries, versus some other effect going
on.

The attached programs use the standard library routines to compute the
assertion that is failing in Octave, specifically the single assertion
"assert(real(acos(1e150)), 0)" that seems to be failing for you and others.
One is a C99 program and one is a C++11 program, both should produce identical
results.

What confuses me even more is I now have a build of Octave with gcc 4.8.4 on a
Ubuntu 14.04 VM, and I don't see a failure in Octave, and both programs
succeed for me. So now I'm not sure on which systems we see success or
failure. Can we get some details from those of you who see failing tests:
OS/distribution version, gcc version, libc version, and architecture?

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