-ffast-math issues

[Orion Poplawski]

Re: https://bugzilla.redhat.com/show_bug.cgi?id=1127544

It appears that shared libraries compiled with -ffast-math (as libopenjpeg.so
is) will call set_fast_math() in the library init code:

Watchpoint 1: $mxcsr

Old value = [ IM DM ZM OM UM PM ]
New value = [ DAZ IM DM ZM OM UM PM FZ ]
0x00007fffe619d112 in set_fast_math () from /lib64/libopenjpeg.so.1
(gdb) bt
#0  0x00007fffe619d112 in set_fast_math () from /lib64/libopenjpeg.so.1
#1  0x00007ffff7deaf2a in call_init (l=<optimized out>, argc=argc at entry=1,
    argv=argv at entry=0x7fffffffd6a8, env=env at entry=0x7fffffffd6b8) at dl-init.c:76

This will then affect the floating point operations of all code run after the
library is loaded, regardless of its use of -ffast-math or not, which can lead
to some unexpected behavior.

This seems like it's a pretty broad and generic problem and I'm wondering how
best to handle it.

-- 
Orion Poplawski
Technical Manager                     303-415-9701 x222
NWRA, Boulder/CoRA Office             FAX: 303-415-9702
3380 Mitchell Lane                       orion at nwra.com
Boulder, CO 80301                   http://www.nwra.com