Date: Thu, 18 Sep 2025 22:29:36 +0800 From: Zhenlei Huang <zlei@FreeBSD.org> To: Nakayama Kenjiro <nakayamakenjiro@gmail.com> Cc: freebsd-hackers@freebsd.org, freebsd-net@freebsd.org Subject: Re: Build failure with Clang/LLVM 22 due to alloc-size diagnostic Message-ID: <9B7C5718-5F5E-46FB-BB97-0F75FB5CD117@FreeBSD.org> In-Reply-To: <CAA_ZtA_184k892=5v0OtZsjweWSgSCX%2BWWR6se_aVCJCAh-apQ@mail.gmail.com> References: <CAA_ZtA_184k892=5v0OtZsjweWSgSCX%2BWWR6se_aVCJCAh-apQ@mail.gmail.com>
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--Apple-Mail=_EB7F8416-2F5E-4DD6-A63A-B90158FE5A54 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset=us-ascii > On Sep 18, 2025, at 7:17 PM, Nakayama Kenjiro = <nakayamakenjiro@gmail.com> wrote: >=20 > Hi, >=20 > There is a new diagnostic, alloc-size, in clang of LLVM22 that warns = if the size given to a malloc is smaller than the size of the struct = pointed to by its destination - = https://github.com/llvm/llvm-project/pull/150028 = <https://github.com/llvm/llvm-project/pull/150028>; > When we enable this option, in_mcast.c triggers this diagnostic, = causing the build to fail. >=20 > ``` > freebsd/sys/netinet/in_mcast.c:749:10: error: allocation of = insufficient size '40' for type 'struct ip_msource' with size '48' = [-Werror,-Walloc-size] > 749 | nims =3D malloc(sizeof(struct in_msource), = M_INMFILTER, > | ^ > ``` >=20 > = https://github.com/freebsd/freebsd-src/blob/stable/15/sys/netinet/in_mcast= .c#L749 = <https://github.com/freebsd/freebsd-src/blob/stable/15/sys/netinet/in_mcas= t.c#L749> > ``` > static int > imf_get_source(struct in_mfilter *imf, const struct sockaddr_in *psin, > struct in_msource **plims) > { > ... > struct ip_msource *ims, *nims; > ... > nims =3D malloc(sizeof(struct in_msource), M_INMFILTER, > M_NOWAIT | M_ZERO); The following lines has this ``` lims =3D (struct in_msource *)nims; ``` So probably assign the alloced memory directly to lims would make Clang = happy, say ``` lims =3D malloc(sizeof( .... ; nims =3D (struct ip_mfilter *)lims; ``` You can have a try with that. Good luck with you ! > ``` >=20 > As the error message explained, the mismatch between struct ip_msource = * and malloc(sizeof(struct in_msource)) triggers the error. >=20 > However, when reading the source code carefully, it seems that *nims = is intentionally of type ip_msource instead of in_msource. > I would like to build with LLVM's alloc-size option enabled, but does = anyone have any good ideas on how to address this problem? Or would it = be better to report it as a false positive to LLVM? Though, I am aware = that there is a workaround to partially disable this option... Best regards, Zhenlei --Apple-Mail=_EB7F8416-2F5E-4DD6-A63A-B90158FE5A54 Content-Transfer-Encoding: quoted-printable Content-Type: text/html; charset=us-ascii <html><head><meta http-equiv=3D"Content-Type" content=3D"text/html; = charset=3Dus-ascii"></head><body style=3D"word-wrap: break-word; = -webkit-nbsp-mode: space; line-break: after-white-space;" class=3D""><br = class=3D""><div><br class=3D""><blockquote type=3D"cite" class=3D""><div = class=3D"">On Sep 18, 2025, at 7:17 PM, Nakayama Kenjiro <<a = href=3D"mailto:nakayamakenjiro@gmail.com" = class=3D"">nakayamakenjiro@gmail.com</a>> wrote:</div><br = class=3D"Apple-interchange-newline"><div class=3D""><div dir=3D"ltr" = class=3D""><div class=3D"">Hi,</div><div class=3D""><br = class=3D""></div><div class=3D"">There is a new diagnostic, alloc-size, = in clang of LLVM22 that warns if the size given to a malloc is smaller = than the size of the struct pointed to by its destination - <a = href=3D"https://github.com/llvm/llvm-project/pull/150028" = class=3D"">https://github.com/llvm/llvm-project/pull/150028</a><br = class=3D"">When we enable this option, in_mcast.c triggers this = diagnostic, causing the build to fail.<br class=3D""><br class=3D"">```<br= class=3D"">freebsd/sys/netinet/in_mcast.c:749:10: error: allocation of = insufficient size '40' for type 'struct ip_msource' with size '48' = [-Werror,-Walloc-size]<br class=3D""> 749 | = nims =3D malloc(sizeof(struct = in_msource), M_INMFILTER,<br class=3D""> | = = ^<br class=3D"">```<br class=3D""><br class=3D""><a = href=3D"https://github.com/freebsd/freebsd-src/blob/stable/15/sys/netinet/= in_mcast.c#L749" = class=3D"">https://github.com/freebsd/freebsd-src/blob/stable/15/sys/netin= et/in_mcast.c#L749</a><br class=3D"">```<br class=3D"">static int<br = class=3D"">imf_get_source(struct in_mfilter *imf, const struct = sockaddr_in *psin,<br class=3D""> struct in_msource = **plims)<br class=3D"">{<br class=3D""> = ...<br class=3D""> struct ip_msource *ims, *nims;<br = class=3D""> ...<br class=3D""> nims =3D = malloc(sizeof(struct in_msource), M_INMFILTER,<br class=3D""> = M_NOWAIT | M_ZERO);<br = class=3D""></div></div></div></blockquote><div><br = class=3D""></div><div>The following lines has = this</div><div>```</div><div>lims =3D (struct in_msource = *)nims;</div><div>```</div><div><br class=3D""></div><div>So probably = assign the alloced memory directly to lims would make Clang happy, = say</div><div>```</div><div>lims =3D malloc(sizeof( .... = ;</div><div>nims =3D (struct ip_mfilter = *)lims;</div><div>```</div><div><br class=3D""></div><div>You can have a = try with that. Good luck with you !</div><br class=3D""><blockquote = type=3D"cite" class=3D""><div class=3D""><div dir=3D"ltr" class=3D""><div = class=3D"">```<br class=3D""><br class=3D"">As the error message = explained, the mismatch between struct ip_msource * and = malloc(sizeof(struct in_msource)) triggers the error.<br class=3D""><br = class=3D"">However, when reading the source code carefully, it seems = that *nims is intentionally of type ip_msource instead of in_msource.<br = class=3D"">I would like to build with LLVM's alloc-size option enabled, = but does anyone have any good ideas on how to address this problem? Or = would it be better to report it as a false positive to LLVM? Though, I = am aware that there is a workaround to partially disable this = option...</div></div> </div></blockquote></div><br class=3D""><div class=3D""> <div>Best regards,</div><div>Zhenlei</div> </div> <br class=3D""></body></html>= --Apple-Mail=_EB7F8416-2F5E-4DD6-A63A-B90158FE5A54--
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