Am Montag, dem 18.09.2023 um 23:26 +0200 schrieb Martin Uecker:
>
> Compared to the previous version I changed the name of the
> warning to "Walloc-size" which matches "Wanalyzer-allocation-size"
> but is still in line with the other -Walloc-something warnings
> we have. I also added it to Wextra.
>
> I found PR71219 that requests the warning and points out that
> it is recommended by the C secure coding guidelines and added
> the PR to the commit log (although the version with cast is not
> diagnosed so far.)
>
> I did not have time to implement the extensions suggested
> on the list, i.e. warn when the size is not a multiple
> of the size of the type and warn for if the size is not
> suitable for a flexible array member. (this is also a bit
> more complicated than it seems)
>
> Bootstrapped and regression tested on x86_64.
>
>
> Martin
>
>
> Add option Walloc-size that warns about allocations that have
> insufficient storage for the target type of the pointer the
> storage is assigned to.
>
> PR c/71219
> gcc:
> * doc/invoke.texi: Document -Walloc-size option.
>
> gcc/c-family:
>
> * c.opt (Walloc-size): New option.
>
> gcc/c:
> * c-typeck.cc (convert_for_assignment): Add warning.
>
> gcc/testsuite:
>
> * gcc.dg/Walloc-size-1.c: New test.
> ---
> gcc/c-family/c.opt | 4 ++++
> gcc/c/c-typeck.cc | 27 +++++++++++++++++++++
> gcc/doc/invoke.texi | 10 ++++++++
> gcc/testsuite/gcc.dg/Walloc-size-1.c | 36 ++++++++++++++++++++++++++++
> 4 files changed, 77 insertions(+)
> create mode 100644 gcc/testsuite/gcc.dg/Walloc-size-1.c
>
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index 7348ad42ee0..9ba08a1fb6d 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-size
> +C ObjC Var(warn_alloc_size) 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 e2bfd2caf85..c759c6245ed 100644
> --- a/gcc/c/c-typeck.cc
> +++ b/gcc/c/c-typeck.cc
> @@ -7384,6 +7384,33 @@ 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 that are not big enough for the target
> + type. */
> + tree fndecl;
> + if (warn_alloc_size
> + && 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)))
> + warning_at (location, OPT_Walloc_size, "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 33befee7d6b..a4fbcf5e1b5 100644
> --- a/gcc/doc/invoke.texi
> +++ b/gcc/doc/invoke.texi
> @@ -8086,6 +8086,16 @@ 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-size
> +@opindex Walloc-size
> +@item -Walloc-size
> +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-size-1.c
> b/gcc/testsuite/gcc.dg/Walloc-size-1.c
> new file mode 100644
> index 00000000000..61806f58192
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/Walloc-size-1.c
> @@ -0,0 +1,36 @@
> +/* Tests the warnings for insufficient allocation size.
> + { dg-do compile }
> + { dg-options "-Walloc-size" }
> + * */
> +#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" } */
> +}
> +
