Refactor hacky ID tables to struct rb_ast_id_table_t

The implementation of a local variable tables was represented as `ID*`,
but it was very hacky: the first element is not an ID but the size of
the table, and, the last element is (sometimes) a link to the next local
table only when the id tables are a linked list.

This change converts the hacky implementation to a normal struct.

1 files changed, 35 insertions, 12 deletions

diff --git a/node.c b/node.c
index 3dea7fe398..180142d089 100644
--- a/node.c
+++ b/node.c
@@ -1043,12 +1043,12 @@ dump_node(VALUE buf, VALUE indent, int comment, const NODE * node)
 	ANN("new scope");
 	ANN("format: [nd_tbl]: local table, [nd_args]: arguments, [nd_body]: body");
 	F_CUSTOM1(nd_tbl, "local table") {
-	    ID *tbl = node->nd_tbl;
+	    rb_ast_id_table_t *tbl = node->nd_tbl;
 	    int i;
-	    int size = tbl ? (int)*tbl++ : 0;
+	    int size = tbl ? tbl->size : 0;
 	    if (size == 0) A("(empty)");
 	    for (i = 0; i < size; i++) {
-		A_ID(tbl[i]); if (i < size - 1) A(",");
+		A_ID(tbl->ids[i]); if (i < size - 1) A(",");
 	    }
 	}
 	F_NODE(nd_args, "arguments");
@@ -1162,7 +1162,7 @@ typedef struct {
 struct node_buffer_struct {
     node_buffer_list_t unmarkable;
     node_buffer_list_t markable;
-    ID *local_tables;
+    struct rb_ast_local_table_link *local_tables;
     VALUE mark_hash;
 };
 
@@ -1205,15 +1205,22 @@ node_buffer_list_free(node_buffer_list_t * nb)
     }
 }
 
+struct rb_ast_local_table_link {
+    struct rb_ast_local_table_link *next;
+    // struct rb_ast_id_table {
+    int size;
+    ID ids[FLEX_ARY_LEN];
+    // }
+};
+
 static void
 rb_node_buffer_free(node_buffer_t *nb)
 {
     node_buffer_list_free(&nb->unmarkable);
     node_buffer_list_free(&nb->markable);
-    ID * local_table = nb->local_tables;
+    struct rb_ast_local_table_link *local_table = nb->local_tables;
     while (local_table) {
-        unsigned int size = (unsigned int)*local_table;
-        ID * next_table = (ID *)local_table[size + 1];
+        struct rb_ast_local_table_link *next_table = local_table->next;
         xfree(local_table);
         local_table = next_table;
     }
@@ -1277,12 +1284,28 @@ rb_ast_node_type_change(NODE *n, enum node_type type)
     }
 }
 
-void
-rb_ast_add_local_table(rb_ast_t *ast, ID *buf)
+rb_ast_id_table_t *
+rb_ast_new_local_table(rb_ast_t *ast, int size)
+{
+    size_t alloc_size = sizeof(struct rb_ast_local_table_link) + size * sizeof(ID);
+    struct rb_ast_local_table_link *link = ruby_xmalloc(alloc_size);
+    link->next = ast->node_buffer->local_tables;
+    ast->node_buffer->local_tables = link;
+    link->size = size;
+
+    return (rb_ast_id_table_t *) &link->size;
+}
+
+rb_ast_id_table_t *
+rb_ast_resize_latest_local_table(rb_ast_t *ast, int size)
 {
-    unsigned int size = (unsigned int)*buf;
-    buf[size + 1] = (ID)ast->node_buffer->local_tables;
-    ast->node_buffer->local_tables = buf;
+    struct rb_ast_local_table_link *link = ast->node_buffer->local_tables;
+    size_t alloc_size = sizeof(struct rb_ast_local_table_link) + size * sizeof(ID);
+    link = ruby_xrealloc(link, alloc_size);
+    ast->node_buffer->local_tables = link;
+    link->size = size;
+
+    return (rb_ast_id_table_t *) &link->size;
 }
 
 void