[PATCH] c++: use auto_vec in cp_parser_template_argument_list

[Jason Merrill]

On 11/9/21 11:02, Patrick Palka wrote:
> Bootstrapped and regtested on x86_64-pc-linux-gnu, OK for trunk?

OK, though I wonder about using releasing_vec instead of auto_vec; 
reusing a previously allocated vec vs. building one on the stack.
> gcc/cp/ChangeLog:
> 
> 	* parser.c (cp_parser_template_argument_list): Use auto_vec
> 	instead of manual memory management.
> ---
>   gcc/cp/parser.c | 35 ++++++++---------------------------
>   1 file changed, 8 insertions(+), 27 deletions(-)
> 
> diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
> index 32de97b08bd..8823399529e 100644
> --- a/gcc/cp/parser.c
> +++ b/gcc/cp/parser.c
> @@ -18558,11 +18558,6 @@ cp_parser_template_name (cp_parser* parser,
>   static tree
>   cp_parser_template_argument_list (cp_parser* parser)
>   {
> -  tree fixed_args[10];
> -  unsigned n_args = 0;
> -  unsigned alloced = 10;
> -  tree *arg_ary = fixed_args;
> -  tree vec;
>     bool saved_in_template_argument_list_p;
>     bool saved_ice_p;
>     bool saved_non_ice_p;
> @@ -18581,16 +18576,15 @@ cp_parser_template_argument_list (cp_parser* parser)
>     parser->non_integral_constant_expression_p = false;
>   
>     /* Parse the arguments.  */
> +  auto_vec<tree, 10> args;
>     do
>       {
> -      tree argument;
> -
> -      if (n_args)
> +      if (!args.is_empty ())
>   	/* Consume the comma.  */
>   	cp_lexer_consume_token (parser->lexer);
>   
>         /* Parse the template-argument.  */
> -      argument = cp_parser_template_argument (parser);
> +      tree argument = cp_parser_template_argument (parser);
>   
>         /* If the next token is an ellipsis, we're expanding a template
>            argument pack. */
> @@ -18610,29 +18604,16 @@ cp_parser_template_argument_list (cp_parser* parser)
>             argument = make_pack_expansion (argument);
>           }
>   
> -      if (n_args == alloced)
> -	{
> -	  alloced *= 2;
> -
> -	  if (arg_ary == fixed_args)
> -	    {
> -	      arg_ary = XNEWVEC (tree, alloced);
> -	      memcpy (arg_ary, fixed_args, sizeof (tree) * n_args);
> -	    }
> -	  else
> -	    arg_ary = XRESIZEVEC (tree, arg_ary, alloced);
> -	}
> -      arg_ary[n_args++] = argument;
> +      args.safe_push (argument);
>       }
>     while (cp_lexer_next_token_is (parser->lexer, CPP_COMMA));
>   
> -  vec = make_tree_vec (n_args);
> +  int n_args = args.length ();
> +  tree vec = make_tree_vec (n_args);
>   
> -  while (n_args--)
> -    TREE_VEC_ELT (vec, n_args) = arg_ary[n_args];
> +  for (int i = 0; i < n_args; i++)
> +    TREE_VEC_ELT (vec, i) = args[i];
>   
> -  if (arg_ary != fixed_args)
> -    free (arg_ary);
>     parser->non_integral_constant_expression_p = saved_non_ice_p;
>     parser->integral_constant_expression_p = saved_ice_p;
>     parser->in_template_argument_list_p = saved_in_template_argument_list_p;
>