Incorrect results from numerical library when using -ftree-ter

[Ian Lance Taylor]

Szabolcs Horvát <szhorvat@gmail.com> writes:

> I am using the Triangle library
> <http://www.cs.cmu.edu/~quake/triangle.html> to generate Delaunay
> triangulations of a large number of points.  When I compile this
> library using the -ftree-ter optimization option only, the library
> gives me incorrect results for certain inputs.  The -ftree-ter  option
> is enabled by optimization level -O1 or higher, which also cause the
> library to return incorrect results.
>
> Question:  Does this indicate that there is a bug in gcc or is it more
> likely that there's a problem in how the library is written?
>
> Unfortunately I am not familiar with the code of Triangle, I just
> compile it and use it.
>
> I tried this with gcc 4.6.3 on Ubuntu and gcc 4.7.0 on Windows (from
> <http://nuwen.net/mingw.html>), both 32-bit.


While a bug in GCC is always possible, it is more likely that there's a
problem in how the library is written.

Ian