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GCC feature req: warn when bitops exceed type size (was: conntrack untracked match is broken)


Hi gcc list,


I am forwarding below's bugreport here(*), to implicitly make aware
of a feature that I deem important to have in a future gcc.



(*) should have posted to bugzilla instead? Don't feel like setting
up a bugmenot tho..

---------- Forwarded message ----------
Date: Mon, 29 Jun 2009 14:34:10
From: Patrick McHardy
To: Jan Engelhardt
Cc: Netfilter Developer Mailing List <netfilter-devel@vger.kernel.org>,
    Philip Craig
Subject: Re: conntrack untracked match is broken (kernel patch)

>On Monday 2009-06-22 08:31, Philip Craig wrote:
>>The problem is that state_mask in 'struct xt_conntrack_mtinfo1' is
>>only 8 bit, but XT_CONNTRACK_STATE_UNTRACKED == 256.
>>Unfortunately, gcc doesn't warn about this for '|=', only for '='.

[i.e. uint8_t x = 0; x |= 256; ]

>
>I smell a gcc-missing-feature there.


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