Re: [PATCH] c++: use auto_vec in cp_parser_template_argument_list

[Jason Merrill via Gcc-patches]

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;