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

From: Ian Lance Taylor <iant at google dot com>
To: bkorb at gnu dot org
Cc: gcc at gcc dot gnu dot org, autoconf-patches at gnu dot org, bug-gnulib at gnu dot org
Date: 01 Jan 2007 16:40:00 -0800
Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
References: <200612300047.kBU0lFwk014817@localhost.localdomain> <871wmht4ab.fsf@penguin.cs.ucla.edu> <10612302258.AA24598@vlsi1.ultra.nyu.edu> <87lkkosz1n.fsf@penguin.cs.ucla.edu> <45970416.80407@adacore.com> <8764bssikm.fsf@penguin.cs.ucla.edu> <571f6b510612310047r3b7ef9acl4a0ab082e88e17a3@mail.gmail.com> <87bqlkmm3r.fsf@penguin.cs.ucla.edu> <4aca3dc20612310641n78e8898euf1c003444e2303eb@mail.gmail.com> <84fc9c000612310645h67066c70vf9eb11af74b639a7@mail.gmail.com> <4aca3dc20612311613r2992db50o851c7d73603b42ef@mail.gmail.com> <87r6ufley1.fsf@penguin.cs.ucla.edu> <m3zm93sc88.fsf@localhost.localdomain> <87zm933wmd.fsf@penguin.cs.ucla.edu> <m3irfqsnge.fsf@localhost.localdomain> <45998B7A.902@gnu.org>

Bruce Korb <bkorb@gnu.org> writes:

> > 2) Add an option like -fstrict-signed-overflow which controls those
> >    cases which appear to be risky.  Turn on that option at -O2.
> 
> Not a good plan.  -O2 should be constrained to disrupting very few
> applications.  (e.g. loop unrolling seems unlikely to cause problems)
> Defer the "appear to be risky" stuff to several years after the warning
> is out.  Please.

Why should we handle signed overflow any differently from strict
aliasing?  We currently enable strict aliasing at -O2.

Ian

References:
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Daniel Berlin
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Paul Eggert
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Ian Lance Taylor
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Paul Eggert
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Ian Lance Taylor
- Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
  - From: Bruce Korb

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