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Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
- From: kenner at vlsi1 dot ultra dot nyu dot edu (Richard Kenner)
- To: dewar at adacore dot com
- Cc: autoconf-patches at gnu dot org, bosch at adacore dot com, bug-gnulib at gnu dot org, dberlin at dberlin dot org, eggert at cs dot ucla dot edu, gcc at gcc dot gnu dot org, richard dot guenther at gmail dot com
- Date: Mon, 01 Jan 2007 12:53:48 EST
- 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> <22C62FE7-259E-43F7-9DB5-5F3A9CF574E2@adacore.com> <45994403.6040008@adacore.com>
> Still, in practical terms, it is true that overflow
> being undefined is unpleasant. In Ada terms, it would
> have seemed better in the C standard to reign in the
> effect of overflow, for instance, merely saying that
> the result is an implementation defined value of the
> type, or the program is terminated. Any other outcome
> seems unreasonable, and in practice unlikely.
My feeling is that GCC, even in its most agressive mode, should treat
overflow as implementation dependent. I don't think that there's any
optimization that depends on it being undefined in the "full sense".