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

From: Gabriel Dos Reis
Subject: Re: changing "configure" to default to "gcc -g -O2 -fwrapv ..."
Date: 31 Dec 2006 10:38:52 +0100

Ian Lance Taylor <address@hidden> writes:

| Gabriel Dos Reis <address@hidden> writes:
| > for this specific function (vrp_int_const_binop), I'm issuing a
| > warning inside the else-if  branch that tests for the overflowed
| > result.  I'm unclear why that is a false positive since the result is
| > known to overflow.  Could you elaborate? 
| Within VRP, calculations are made on ranges.  The upper and lower
| limits of those ranges need not actually appear in the program.  If
| you warn whenever vrp_int_const_binop produces an overflow, you will
| get an enormous number of false positives.

Thanks for this explanation.

| I have a patch which issues warnings whenever gcc assumes that signed
| overflow is undefined, except in loop IV calculations.  I'm tweaking
| it to see whether it is possible to bootstrap gcc with this patch.  It
| currently builds libcpp with no warnings, but falls over on this code
| in decDivideOp in decNumber.c in libdecnumber:

OK, I see; since today is a bit special I may not be able to get back
to you as quickly as I would like.

-- Gaby

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