On Mon, 2013-03-04 at 09:39 -0500, Bob Rossi wrote:
> Hi,
> 
> I'm using valgrind on a small Ada program (attached).
> 
> The Ada program runs fine on the linux host, it prints 8.5.
> 
> When I run the program through valgrind, it prints 0.0.
> 
> Any ideas why this might be?
> 
> I tried this with gnatmake with gnu 4.1.2 and gnu 4.2 on,
> 
> $ uname -a
> Linux maple 2.6.32-22-generic-pae #36-Ubuntu SMP Thu Jun 3 23:14:23 UTC
> 2010 i686 GNU/Linux
GNAT runtime is implementing various features (e.g. float images)
by using long_long_float, which are 80 bits floats.
As these are not properly supported by Valgrind, this can introduce
numerical differences/errors.
See e.g. https://bugs.kde.org/show_bug.cgi?id=130358

Now, I have no idea if your specific bug is caused by this.
If you use a recent Valgrind version, you might debug the GNAT runtime
native and under Valgrind (using gdb/vgdb) and compare the floating
point behaviour between the native and the valgrind execution.

(the runtime must be compiled with debug)

Philippe



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