Date: Thu, 18 Sep 2025 19:42:03 +0000 From: Paul Vixie <paul@redbarn.org> To: Nakayama Kenjiro <nakayamakenjiro@gmail.com>, freebsd-net@freebsd.org Cc: freebsd-hackers@freebsd.org, freebsd-net@freebsd.org, Zhenlei Huang <zlei@freebsd.org> Subject: Re: Build failure with Clang/LLVM 22 due to alloc-size diagnostic Message-ID: <4985340.OV4Wx5bFTl@localhost> In-Reply-To: <9B7C5718-5F5E-46FB-BB97-0F75FB5CD117@FreeBSD.org> References: <CAA_ZtA_184k892=5v0OtZsjweWSgSCX%2BWWR6se_aVCJCAh-apQ@mail.gmail.com> <9B7C5718-5F5E-46FB-BB97-0F75FB5CD117@FreeBSD.org>
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On Donderdag 18 September 2025 14:29:36 UTC Zhenlei Huang wrote:
> > On Sep 18, 2025, at 7:17 PM, Nakayama Kenjiro <nakayamakenjiro@gmail.com>
> > ...
> > freebsd/sys/netinet/in_mcast.c:749:10: error: allocation of insufficient
> > size '40' for type 'struct ip_msource' with size '48'
> > ...
> The following lines has this
> ```
> lims = (struct in_msource *)nims;
> ```
>
> So probably assign the alloced memory directly to lims would make Clang
> happy, say ```
> lims = malloc(sizeof( .... ;
> nims = (struct ip_mfilter *)lims;
> ```
>
> You can have a try with that. Good luck with you !
ideally, clang will eventually get around to complaining about that type cast on the same
basis (destination points to a longer object than the source.) is there a reason we're not
using a union{} for this data?
--
Paul Vixie
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<body><p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">On Donderdag 18 September 2025 14:29:36 UTC Zhenlei Huang wrote:</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> > On Sep 18, 2025, at 7:17 PM, Nakayama Kenjiro <nakayamakenjiro@gmail.com></p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> > ...</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> > freebsd/sys/netinet/in_mcast.c:749:10: error: allocation of insufficient</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> > size '40' for type 'struct ip_msource' with size '48'</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> > ...</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> The following lines has this</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> ```</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> lims = (struct in_msource *)nims;</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> ```</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> </p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> So probably assign the alloced memory directly to lims would make Clang</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> happy, say ```</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> lims = malloc(sizeof( .... ;</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> nims = (struct ip_mfilter *)lims;</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> ```</p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> </p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">> You can have a try with that. Good luck with you !</p>
<br /><p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">ideally, clang will eventually get around to complaining about that type cast on the same basis (destination points to a longer object than the source.) is there a reason we're not using a union{} for this data?</p>
<br /><p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">-- </p>
<p style="margin-top:0;margin-bottom:0;margin-left:0;margin-right:0;">Paul Vixie</p>
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