r194403 - Using an invalid -O falls back on -O3 instead of an error

[Hal Finkel]

----- Original Message -----
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> 
> 
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> On Mon, Nov 11, 2013 at 11:01 AM, Sylvestre Ledru <
> sylvestre at debian.org > wrote:
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> Using an invalid -O falls back on -O3 instead of an error
> 
> Summary:
> Currently with clang:
> $ clang -O20 foo.c
> error: invalid value '20' in '-O20'
> 
> With the patch:
> $ clang -O20 foo.c
> warning: invalid value '20' in '-O20'. Fall back on value '3'
> Sorry that I missed the original thread here, but why is this the
> desired behavior?

Because it is the sensible thing to do ;) -- Users tend to assume that the higher the number the more optimizations they're getting. Having -O5 do less than -O3 would be very confusing. If we end up with a -O4, then we'll change that to be the fall back for large -O<n>, etc.

 -Hal

> 
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> My preference would be to have '-O' be the fallback, and that in turn
> be equivalent to '-O2' which is often viewed as a reasonable default
> level of optimization.
> 
> 
> I just don't like reading too munch into invalid numbers given to
> -O...
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-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory