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 > <gcc-patches@gcc.gnu.org> wrote: > > > > > > > > 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. > > > > > > Bootstrapped and regression tested on x86. > > > > > > Martin > > > > > > > > Add option Walloc-type that warns about allocations that have > > insufficient storage for the target type of the pointer the > > storage is assigned to. > > > > gcc: > > * doc/invoke.texi: Document -Wstrict-flex-arrays option. > > > > gcc/c-family: > > > > * c.opt (Walloc-type): New option. > > > > gcc/c: > > * c-typeck.cc (convert_for_assignment): Add Walloc-type warning. > > > > gcc/testsuite: > > > > * gcc.dg/Walloc-type-1.c: New test. > > > > > > 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. > > > > +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= > > 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=<bytes> 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); > > > > + /* Warn of new allocations are not big enough for the target > > type. */ > > + tree fndecl; > > + if (warn_alloc_type > > + && TREE_CODE (rhs) == CALL_EXPR > > + && (fndecl = get_callee_fndecl (rhs)) != NULL_TREE > > + && DECL_IS_MALLOC (fndecl)) > > + { > > + tree fntype = TREE_TYPE (fndecl); > > + tree fntypeattrs = TYPE_ATTRIBUTES (fntype); > > + tree alloc_size = lookup_attribute ("alloc_size", > > fntypeattrs); > > + if (alloc_size) > > + { > > + tree args = TREE_VALUE (alloc_size); > > + int idx = TREE_INT_CST_LOW (TREE_VALUE (args)) - 1; > > + /* For calloc only use the second argument. */ > > + if (TREE_CHAIN (args)) > > + idx = TREE_INT_CST_LOW (TREE_VALUE (TREE_CHAIN > > (args))) - 1; > > + tree arg = CALL_EXPR_ARG (rhs, idx); > > + if (TREE_CODE (arg) == 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 = malloc (sizeof (int) + 2); // probably intended malloc > (sizeof (int) * 2) > > 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 = __builtin_malloc (sizeof(int) + 2); > | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ > > 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 = TYPE_ADDR_SPACE (ttl); > > asr = 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 > > > > +@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 <stdlib.h> > > +#include <alloca.h> > > + > > +struct b { int x[10]; }; > > + > > +void fo0(void) > > +{ > > + struct b *p = malloc(sizeof *p); > > +} > > + > > +void fo1(void) > > +{ > > + struct b *p = malloc(sizeof p); /* { dg- > > warning "allocation of insufficient size" } */ > > +} > > + > > +void fo2(void) > > +{ > > + struct b *p = alloca(sizeof p); /* { dg- > > warning "allocation of insufficient size" } */ > > +} > > + > > +void fo3(void) > > +{ > > + struct b *p = 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" } */ > > +} > > + > > + > > > > > > -- Univ.-Prof. Dr. rer. nat. Martin Uecker Graz University of Technology Institute of Biomedical Imaging