[Pkg-octave-devel] Bug#871214: Bug#871214: octave-image FTBFS on i386: test hangs

Sébastien Villemot sebastien at debian.org
Tue Aug 15 18:08:58 UTC 2017


On Thu, Aug 10, 2017 at 02:42:42PM +0300, Adrian Bunk wrote:
> On Thu, Aug 10, 2017 at 09:31:32AM +0200, Rafael Laboissière wrote:
> > 
> > I would guess that the culprit is the following unit test in bwdist:
> > 
> > ## The quasi-euclidean method is apparently sensitive to a machine precision
> > ## error that happens in x86 systems only. This test will cause an endless
> > ## loop in case of a regression.
> >...
> 
> That explains why the problem happens on i386 (where the 387 FPU
> that internally uses 80-bit precision is used) but not on amd64
> (where gcc defaults to using SSE instead of the 387).
> 
> If the problem is only in the test case,
> it should be disabled on any-i386.
> 
> But if the difference is actually considered a bug,
> then the following in debian/rules fixes the problem:
> 
> DEB_HOST_ARCH ?= $(shell dpkg-architecture -qDEB_HOST_ARCH)
> 
> ifneq (,$(filter $(DEB_HOST_ARCH), i386))
>     export DEB_CXXFLAGS_MAINT_APPEND=-ffloat-store
> endif

Thanks Adrian for suggesting this solution.

However, it should be mentioned that this option has a significant performance
cost (since it basically adds a memory access after each floating point
computation).

I am not familiar enough with octave-image to decide whether IEEE compliance is
more important than performance, though.

-- 
⢀⣴⠾⠻⢶⣦   Sébastien Villemot
⣾⠁⢠⠒⠀⣿⡁  Debian Developer
⢿⡄⠘⠷⠚⠋⠀  http://sebastien.villemot.name
⠈⠳⣄      http://www.debian.org
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