[cctbxbb] Strange segementation fault

[Luc Bourhis]

Hi Armin,

> When I import from the cctbx and perform a division through zero (with
> array objects from numpy) something segfaults.

During the first import of any cctbx module, some code is run to  
switch on the trapping of floating point exceptions. Thus after that  
import, divsion-by-zero, NaN-production and overflows result in a  
stacktrace indeed, which is usually not the default.

You should see a message telling you about one way to suppress that  
behaviour (after the stacktrace). You can indeed set any of the  
following environment variable: BOOST_ADAPTBX_FE_OVERFLOW_DEFAULT,  
BOOST_ADAPTBX_FE_INVALID_DEFAULT, BOOST_ADAPTBX_FE_DIVBYZERO_DEFAULT,  
BOOST_ADAPTBX_FPE_DEFAULT. They respectively revert to the default  
behaviour of your platform for respectively overflows, NaN, division  
by zero and all of those three.

There is a programmatic way to suppress trapping too.

from boost.python import floating_point_exceptions
# Then any combination of the following
floating_point_exceptions.division_by_zero_trapped = False
floating_point_exceptions.invalid_trapped = False
floating_point_exceptions.overflow_trapped = False

> I did not observe this behaviour on windows

We have not installed those traps on Windows indeed. Only on Linux and  
MacOS X.


Luc Bourhis
Computer Scientist
Chemical Crystallography Laboratory
University of Durham, UK



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