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

From: Andrew Pinski
Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
Date: Fri, 29 Dec 2006 11:13:16 -0500 (EST)

> Paul Eggert <address@hidden> writes:
> >     * NEWS: AC_PROG_CC, AC_PROG_CXX, and AC_PROG_OBJC now take an
> >     optional second argument specifying the default optimization
> >     options for GCC.  These optimizations now default to "-O2 -fwrapv"
> >     instead of to "-O2".  This partly attacks the problem reported by
> >     Ralf Wildenhues in
> >     <>
> >     and in <>.
> Does anybody think that Paul's proposed patch to autoconf would be
> better than changing VRP?

I think both ways are incorrect way forward.
What about coding the loops like:

if (sizeof(time_t) == sizeof(unsigned int))
  // do loop using unsigned int
  // convert to time_t and then see if an overflow happened
//etc. for the other type

This way you don't depend on either implemenetation defined behavior
of converting between integer with different sizes and undefined behavior
with signed type overflow.

Andrew Pinski

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