From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mailrelay.tugraz.at (mailrelay.tugraz.at [129.27.2.202]) by sourceware.org (Postfix) with ESMTPS id 73A883858C66 for ; Tue, 1 Aug 2023 07:51:20 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.2 sourceware.org 73A883858C66 Authentication-Results: sourceware.org; dmarc=pass (p=quarantine dis=none) header.from=tugraz.at Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=tugraz.at Received: from [192.168.0.171] (84-115-221-158.cable.dynamic.surfer.at [84.115.221.158]) by mailrelay.tugraz.at (Postfix) with ESMTPSA id 4RFS3M6wswz1LM0M; Tue, 1 Aug 2023 09:51:11 +0200 (CEST) DKIM-Filter: OpenDKIM Filter v2.11.0 mailrelay.tugraz.at 4RFS3M6wswz1LM0M DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=tugraz.at; s=mailrelay; t=1690876272; bh=UMRAtlYCp+/CLvCqk37EoGQlNP8+s8BNH0HToU+YYdg=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=lmDBtoMUWamp67vMUUkBseCbwZ50SorgFqA7HpBgE10HNu9JPdg2W5K5/Rr5ew7sR mmWrWJSS4jtseWhzBDr51SdBwwOLhJW328PjFk8HKOpZYnrI8bhJzW0ng11dDd27x1 qhJcxreAhd+8NF7CPYCJZC6CKXLd2XuHWguuSqD8= Message-ID: Subject: Re: [C PATCH]: Add Walloc-type to warn about insufficient size in allocations From: Martin Uecker To: Prathamesh Kulkarni Cc: gcc-patches@gcc.gnu.org, Joseph Myers Date: Tue, 01 Aug 2023 09:51:11 +0200 In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.46.4-2 MIME-Version: 1.0 X-TUG-Backscatter-control: G/VXY7/6zeyuAY/PU2/0qw X-Spam-Scanner: SpamAssassin 3.003001 X-Spam-Score-relay: -0.4 X-Scanned-By: MIMEDefang 2.74 on 129.27.10.117 X-Spam-Status: No, score=-11.8 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,GIT_PATCH_0,RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_PASS,TXREP,T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: Am Dienstag, dem 01.08.2023 um 02:11 +0530 schrieb Prathamesh Kulkarni: > On Fri, 21 Jul 2023 at 16:52, Martin Uecker via Gcc-patches > wrote: > >=20 > >=20 > >=20 > > This patch adds a warning for allocations with insufficient size > > based on the "alloc_size" attribute and the type of the pointer > > the result is assigned to. While it is theoretically legal to > > assign to the wrong pointer type and cast it to the right type > > later, this almost always indicates an error. Since this catches > > common mistakes and is simple to diagnose, it is suggested to > > add this warning. > >=20 > >=20 > > Bootstrapped and regression tested on x86. > >=20 > >=20 > > Martin > >=20 > >=20 > >=20 > > Add option Walloc-type that warns about allocations that have > > insufficient storage for the target type of the pointer the > > storage is assigned to. > >=20 > > gcc: > > * doc/invoke.texi: Document -Wstrict-flex-arrays option. > >=20 > > gcc/c-family: > >=20 > > * c.opt (Walloc-type): New option. > >=20 > > gcc/c: > > * c-typeck.cc (convert_for_assignment): Add Walloc-type warning= . > >=20 > > gcc/testsuite: > >=20 > > * gcc.dg/Walloc-type-1.c: New test. > >=20 > >=20 > > diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt > > index 4abdc8d0e77..8b9d148582b 100644 > > --- a/gcc/c-family/c.opt > > +++ b/gcc/c-family/c.opt > > @@ -319,6 +319,10 @@ Walloca > > C ObjC C++ ObjC++ Var(warn_alloca) Warning > > Warn on any use of alloca. > >=20 > > +Walloc-type > > +C ObjC Var(warn_alloc_type) Warning > > +Warn when allocating insufficient storage for the target type of the > > assigned pointer. > > + > > Walloc-size-larger-than=3D > > C ObjC C++ LTO ObjC++ Var(warn_alloc_size_limit) Joined Host_Wide_Int > > ByteSize Warning Init(HOST_WIDE_INT_MAX) > > -Walloc-size-larger-than=3D Warn for calls to allocation > > functions that > > diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc > > index 7cf411155c6..2e392f9c952 100644 > > --- a/gcc/c/c-typeck.cc > > +++ b/gcc/c/c-typeck.cc > > @@ -7343,6 +7343,32 @@ convert_for_assignment (location_t location, > > location_t expr_loc, tree type, > > "request for implicit conversion " > > "from %qT to %qT not permitted in C++", rhstype, > > type); > >=20 > > + /* Warn of new allocations are not big enough for the target > > type. */ > > + tree fndecl; > > + if (warn_alloc_type > > + && TREE_CODE (rhs) =3D=3D CALL_EXPR > > + && (fndecl =3D get_callee_fndecl (rhs)) !=3D NULL_TREE > > + && DECL_IS_MALLOC (fndecl)) > > + { > > + tree fntype =3D TREE_TYPE (fndecl); > > + tree fntypeattrs =3D TYPE_ATTRIBUTES (fntype); > > + tree alloc_size =3D lookup_attribute ("alloc_size", > > fntypeattrs); > > + if (alloc_size) > > + { > > + tree args =3D TREE_VALUE (alloc_size); > > + int idx =3D TREE_INT_CST_LOW (TREE_VALUE (args)) - 1; > > + /* For calloc only use the second argument. */ > > + if (TREE_CHAIN (args)) > > + idx =3D TREE_INT_CST_LOW (TREE_VALUE (TREE_CHAIN > > (args))) - 1; > > + tree arg =3D CALL_EXPR_ARG (rhs, idx); > > + if (TREE_CODE (arg) =3D=3D INTEGER_CST > > + && tree_int_cst_lt (arg, TYPE_SIZE_UNIT (ttl))) > Hi Martin, > Just wondering if it'd be a good idea perhaps to warn if alloc size is > not a multiple of TYPE_SIZE_UNIT instead of just less-than ? > So it can catch cases like: > int *p =3D malloc (sizeof (int) + 2); // probably intended malloc > (sizeof (int) * 2) >=20 > FWIW, this is caught using -fanalyzer: > f.c: In function 'f': > f.c:3:12: warning: allocated buffer size is not a multiple of the > pointee's size [CWE-131] [-Wanalyzer-allocation-size] > 3 | int *p =3D __builtin_malloc (sizeof(int) + 2); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >=20 > Thanks, > Prathamesh Yes, this is probably a good idea. It might need special logic for flexible array members then... Martin > > + warning_at (location, OPT_Walloc_type, "allocation of > > " > > + "insufficient size %qE for type %qT with > > " > > + "size %qE", arg, ttl, TYPE_SIZE_UNIT > > (ttl)); > > + } > > + } > > + > > /* See if the pointers point to incompatible address spaces. */ > > asl =3D TYPE_ADDR_SPACE (ttl); > > asr =3D TYPE_ADDR_SPACE (ttr); > > diff --git a/gcc/doc/invoke.texi b/gcc/doc/invoke.texi > > index 88e3c625030..6869bed64c3 100644 > > --- a/gcc/doc/invoke.texi > > +++ b/gcc/doc/invoke.texi > > @@ -8076,6 +8076,15 @@ always leads to a call to another @code{cold} > > function such as wrappers of > > C++ @code{throw} or fatal error reporting functions leading to > > @code{abort}. > > @end table > >=20 > > +@opindex Wno-alloc-type > > +@opindex Walloc-type > > +@item -Walloc-type > > +Warn about calls to allocation functions decorated with attribute > > +@code{alloc_size} that specify insufficient size for the target type > > of > > +the pointer the result is assigned to, including those to the built-in > > +forms of the functions @code{aligned_alloc}, @code{alloca}, > > @code{calloc}, > > +@code{malloc}, and @code{realloc}. > > + > > @opindex Wno-alloc-zero > > @opindex Walloc-zero > > @item -Walloc-zero > > diff --git a/gcc/testsuite/gcc.dg/Walloc-type-1.c > > b/gcc/testsuite/gcc.dg/Walloc-type-1.c > > new file mode 100644 > > index 00000000000..bc62e5e9aa3 > > --- /dev/null > > +++ b/gcc/testsuite/gcc.dg/Walloc-type-1.c > > @@ -0,0 +1,37 @@ > > +/* Tests the warnings for insufficient allocation size. > > + { dg-do compile } > > + * { dg-options "-Walloc-type" } > > + * */ > > +#include > > +#include > > + > > +struct b { int x[10]; }; > > + > > +void fo0(void) > > +{ > > + struct b *p =3D malloc(sizeof *p); > > +} > > + > > +void fo1(void) > > +{ > > + struct b *p =3D malloc(sizeof p); /* { dg- > > warning "allocation of insufficient size" } */ > > +} > > + > > +void fo2(void) > > +{ > > + struct b *p =3D alloca(sizeof p); /* { dg- > > warning "allocation of insufficient size" } */ > > +} > > + > > +void fo3(void) > > +{ > > + struct b *p =3D calloc(1, sizeof p); /* { dg-warning > > "allocation of insufficient size" } */ > > +} > > + > > +void g(struct b* p); > > + > > +void fo4(void) > > +{ > > + g(malloc(4)); /* { dg-warning "allocation of > > insufficient size" } */ > > +} > > + > > + > >=20 > >=20 > >=20 --=20 Univ.-Prof. Dr. rer. nat. Martin Uecker Graz University of Technology Institute of Biomedical Imaging