bin/137869: cc --fast-math leads to nan% CPU consumption in ps and top

gavin at gavin at
Mon Aug 17 11:37:35 UTC 2009

Synopsis: cc --fast-math leads to nan% CPU consumption in ps and top

State-Changed-From-To: open->feedback
State-Changed-By: gavin
State-Changed-When: Mon Aug 17 11:28:34 UTC 2009
To submitter: Looking at the man page for gcc suggests that -ffast-math enables
-fno-math-errno, -funsafe-math-optimizations, -fno-trapping-math,
-ffinite-math-only, -fno-rounding-math, -fno-signaling-nans and fcx-limited-range.

Perhaps you could spend some time and figure out which of these options are
breaking top and ps?

Although, the man page also says about -ffast-math:
.  This option [...] can result in incorrect output for programs which depend on
.  an exact implementation of IEEE or ISO rules/specifications for math functions.
so it may well just because top and ps depend on the math functions being

Lastly, compiling with unusual optimisation settings isn't supported, so it
may be that this bug isn't fixed unless there is a real underlying problem.

Responsible-Changed-From-To: freebsd-bugs->gavin
Responsible-Changed-By: gavin
Responsible-Changed-When: Mon Aug 17 11:28:34 UTC 2009

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