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[Bug c/42908] gcc -O2 -Wall doesn't warn about strict aliasing
- From: "shana at jitted dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Feb 2010 16:13:13 -0000
- Subject: [Bug c/42908] gcc -O2 -Wall doesn't warn about strict aliasing
- References: <bug-42908-18727@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from shana at jitted dot com 2010-02-03 16:13 -------
IMHO, it's not good for strict aliasing warnings on level 2 to be optional and
not included in -Wall by default. As it stands right now, gcc does not warn you
even if it knows your code is 1) breaking the rules, and 2) the assignments
that break the rules are going to be touched by optimizations.
Optimizing away an assignment because that assignment breaks a rule is always a
potential danger. Now I know that the reasoning to not show those warnings by
default is that it can give you false positives, but a false positive in this
case is when you *are* breaking the rules, but an optimization *might* or
*might not* break your code. IMHO, just because your code might not break
doesn't mean the warning is not needed. A developer really needs to know he's
breaking the rules here, regardless of whether things blow up or not.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42908