Re: Infinite loop with GCC 4.3

[John Mandereau]

On 2008/05/26, Joe Neeman wrote:
> Attached is the smallest example that I could find that reproduces the
> problem. With g++ 4.3.0 on Fedora 9, I get an infinite loop with -O1 but
> immediate termination with -O0. With g++ 4.2.3 on Debian, I get
> termination regardless of the optimisation setting.
> 
> I think it is also easy to argue that the program should terminate,
> regardless of rounding (the value of 'i' should be the same every time
> the loop executes. So on the second time through, 'x' should be at least
> as large as 'i').

I agree.


> Can you reproduce? If so, I'll go bug the gcc people.

Regardless of the g++ version I tried (4.3.0, 4.2.4 and 4.1.2), the
small example terminates immediately with -O0, but goes into an infinite
loop with -O1 and -O2.  In case it matters, my box run with an Intel
Celeron M, Fedora 9 comes with glibc-2.8 (all compiled binaries are
linked to /lib/libm.so.6), and I didn't bother changing LD_LIBRARY_PATH
(which was /home/lilydev/gcc-4.1.2/lib when I compiled the example with
all GCC versions).

I don't know how to interpret this result.  LilyPond compiled with g++
4.1.2 and -O2 works well, whereas your example doesn't; does this mean
the problem is different between Lily and this example?

I hope this can help you make a bug report to GCC
John