Re: [PATCH] c++: Enable -Walloc-size and -Wcalloc-transposed-args warnings for C++

[Jason Merrill <jason@redhat.com>]

On 12/20/23 14:20, Jakub Jelinek wrote:
> Hi!
> 
> The following patch enables the -Walloc-size and -Wcalloc-transposed-args
> warnings for C++ as well.
> 
> Ok for trunk if it passes bootstrap/regtest?
> 
> 2023-12-20  Jakub Jelinek  <jakub@redhat.com>
> 
> gcc/c-family/
> 	* c.opt (Walloc-size): Enable also for C++ and ObjC++.
> gcc/cp/
> 	* cp-gimplify.cc (cp_genericize_r): If warn_alloc_size, call
> 	warn_for_alloc_size for -Walloc-size diagnostics.
> 	* semantics.cc (finish_call_expr): If warn_calloc_transposed_args,
> 	call warn_for_calloc for -Wcalloc-transposed-args diagnostics.
> gcc/testsuite/
> 	* g++.dg/warn/Walloc-size-1.C: New test.
> 	* g++.dg/warn/Wcalloc-transposed-args-1.C: New test.
> 
> --- gcc/c-family/c.opt.jj	2023-12-20 11:31:07.897806698 +0100
> +++ gcc/c-family/c.opt	2023-12-20 20:02:36.889910599 +0100
> @@ -332,7 +332,7 @@ C ObjC C++ ObjC++ Var(warn_alloca) Warni
>   Warn on any use of alloca.
>   
>   Walloc-size
> -C ObjC Var(warn_alloc_size) Warning LangEnabledBy(C ObjC, Wextra)
> +C ObjC C++ ObjC++ Var(warn_alloc_size) Warning LangEnabledBy(C ObjC C++ ObjC++, Wextra)
>   Warn when allocating insufficient storage for the target type of the assigned pointer.
>   
>   Walloc-size-larger-than=
> --- gcc/cp/cp-gimplify.cc.jj	2023-12-15 10:08:53.877236695 +0100
> +++ gcc/cp/cp-gimplify.cc	2023-12-20 20:10:59.689914648 +0100
> @@ -2048,6 +2048,25 @@ cp_genericize_r (tree *stmt_p, int *walk
>   
>       case NOP_EXPR:
>         *stmt_p = predeclare_vla (*stmt_p);
> +
> +      /* Warn of new allocations that are not big enough for the target
> +	 type.  */
> +      if (warn_alloc_size
> +	  && TREE_CODE (TREE_OPERAND (stmt, 0)) == CALL_EXPR
> +	  && POINTER_TYPE_P (TREE_TYPE (stmt)))
> +	{
> +	  if (tree fndecl = get_callee_fndecl (TREE_OPERAND (stmt, 0)))
> +	    if (DECL_IS_MALLOC (fndecl))
> +	      {
> +		tree attrs = TYPE_ATTRIBUTES (TREE_TYPE (fndecl));
> +		tree alloc_size = lookup_attribute ("alloc_size", attrs);
> +		if (alloc_size)
> +		  warn_for_alloc_size (EXPR_LOCATION (stmt),
> +				       TREE_TYPE (TREE_TYPE (stmt)),
> +				       TREE_OPERAND (stmt, 0), alloc_size);
> +	      }
> +	}
> +
>         if (!wtd->no_sanitize_p
>   	  && sanitize_flags_p (SANITIZE_NULL | SANITIZE_ALIGNMENT)
>   	  && TYPE_REF_P (TREE_TYPE (stmt)))
> --- gcc/cp/semantics.cc.jj	2023-12-14 07:49:53.150580801 +0100
> +++ gcc/cp/semantics.cc	2023-12-20 20:13:33.773772759 +0100
> @@ -2939,15 +2939,24 @@ finish_call_expr (tree fn, vec<tree, va_
>   
>         if (!result)
>   	{
> -	  if (warn_sizeof_pointer_memaccess
> +	  tree alloc_size_attr = NULL_TREE;
> +	  if (warn_calloc_transposed_args
> +	      && TREE_CODE (fn) == FUNCTION_DECL
> +	      && (alloc_size_attr
> +		  = lookup_attribute ("alloc_size",
> +				      TYPE_ATTRIBUTES (TREE_TYPE (fn)))))
> +	    if (TREE_VALUE (alloc_size_attr) == NULL_TREE
> +		|| TREE_CHAIN (TREE_VALUE (alloc_size_attr)) == NULL_TREE)
> +	      alloc_size_attr = NULL_TREE;
> +	  if ((warn_sizeof_pointer_memaccess || alloc_size_attr)
>   	      && (complain & tf_warning)
>   	      && !vec_safe_is_empty (*args)
>   	      && !processing_template_decl)
>   	    {
> -	      location_t sizeof_arg_loc[3];
> -	      tree sizeof_arg[3];
> +	      location_t sizeof_arg_loc[6];
> +	      tree sizeof_arg[6];

Why do we need to check 6 args for calloc?  The patch is OK, just wondering.

Jason