turning off optimization on a code segment

[Frédéric BOIS]

Hi!

I have a problem with a code segment (actually one line). If I compile
with no optimization (with or without debugging enabled) it's fine.
If I optimize (again with or without debugging) it fails for one
mis-computed line:
pifn->bOn = (*pdTime < *pdTnext);
if *pdTime is equal to *pdTnext (checked in gdb: print *pdTime -
*pdTnext returns zero and print  (*pdTime < *pdTnext) returns 0 too)
the computed value of pifn->bOn is "1", and that's an error. I don't
know exactly what to do and I am in a rush. I could try to go around 
all that, but an easy quick fix might be to turn off the optimization
of the routine. However, I don't know how to do that.
I get that with gcc 3.3.3 (suze linux), and on v 4.3.0 under debian
linux.

Thanks if you can help.

Frederic