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Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."

From: Ian Lance Taylor
Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
Date: 01 Jan 2007 08:05:34 -0800
User-agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.4

Gabriel Dos Reis <address@hidden> writes:

> I do hope your and Richard G's constructive search for middle ground
> will find echoes within the middle-end maintainers.

This seems likely, since Richard and I are two of the three middle-end
maintainers, and I don't recall hearing from the other one in this

> I do appreciate your preliminary patch -- and I'm sure Paul find it
> useful too, as tool to advance in this discussion.  I suspect that,
> what is not clear is whether "the other side" (I hate that expression)
> is amenable to agreeing on that course or whether the seemingly
> prevalent attitude "but it is undefined; but it is not C" is the
> opinion of the majority of middle-end maintainers. 

I don't personally see that as the question.  This code is undefined,
and, therefore, is in some sense not C.  If we take any other
attitude, then we will be definining and supporting a different
language.  I think that relatively few people want the language "C
plus signed integers wrap", which is the language we support with the
-fwrapv option.

What I think we need to do is introduce a warning option to optionally
warn about optimizations which are unusually risky for existing code.
And I think we need to provide more fine-grained control over which
optimizations we implement.


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