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From: "veksler at il dot ibm dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/21951] [4.0 only] std::vector.reserve() unusable with -Werror -Wall -O -fno-exceptions
Date: Wed, 08 Jun 2005 14:43:00 -0000 [thread overview]
Message-ID: <20050608144342.1310.qmail@sourceware.org> (raw)
In-Reply-To: <20050607175818.21951.dank@kegel.com>
------- Additional Comments From veksler at il dot ibm dot com 2005-06-08 14:43 -------
(In reply to comment #7)
> It sure as hell is for those shops that require -Werror.
>
> But ok, I'll be happy if it's fixed for 4.0.2.
I think that your argument (as phrased) does not hold.
Maybe you meant "It sure as hell is for those shops that require -Werror,
in this particular instance".
(Pardon my language, I just quoted the original ;-)
Consider:
1. 1: int main()
2: {
3: int a;
4: never_return(); // the halting problem
5: return a; // Uninitialized variable?
6: }
This is perfectly valid code and well defined, yet -Wall -Werror
will reject it. No compiler will ever be able to determine if
line 5 is ever reached.
2. 1: int main()
2: {
3: int a;
4: if(foo())
5: a= bar();
6: if(foo())
7: return a; // Uninitialized variable?
8: return 0;
9: }
Again, no compiler will be able to prove that a nontrivial foo() does
not change over time (unless declared const/pure/whatever).
And as a result, -Wall -Werror will reject valid code.
In both examples, the user has a simple work-around, initialize 'a'.
Adding initialization will make the code more stable, as foo() is
no longer constrained to be const/pure (forgive me for not remembering if
it is called pure or const).
In contrast (as mentioned in comment #4), this PR and PR 21183 do not
give the user the tools to shut this specific diagnostic instance up.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21951
next prev parent reply other threads:[~2005-06-08 14:43 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-06-07 17:58 [Bug c++/21951] New: [gcc-4.0 regression, rejects-valid] " dank at kegel dot com
2005-06-07 18:00 ` [Bug c++/21951] " pinskia at gcc dot gnu dot org
2005-06-07 18:12 ` pcarlini at suse dot de
2005-06-07 18:17 ` pinskia at gcc dot gnu dot org
2005-06-07 19:46 ` veksler at il dot ibm dot com
2005-06-07 23:28 ` [Bug libstdc++/21951] " bangerth at dealii dot org
2005-06-08 13:20 ` [Bug libstdc++/21951] [4.0 only] " pinskia at gcc dot gnu dot org
2005-06-08 13:57 ` dank at kegel dot com
2005-06-08 14:11 ` veksler at il dot ibm dot com
2005-06-08 14:43 ` veksler at il dot ibm dot com [this message]
2005-06-08 19:16 ` bkoz at gcc dot gnu dot org
2005-06-11 11:25 ` dank at kegel dot com
2005-06-11 19:29 ` dank at kegel dot com
2005-06-12 15:02 ` pinskia at gcc dot gnu dot org
2005-07-01 19:10 ` geoffk at gcc dot gnu dot org
2005-07-01 19:42 ` dank at kegel dot com
2005-07-16 21:12 ` pinskia at gcc dot gnu dot org
[not found] <bug-21951-3350@http.gcc.gnu.org/bugzilla/>
2005-10-24 1:31 ` pinskia at gcc dot gnu dot org
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