diff --git a/ast.c b/ast.c
index 96116d43eb..8139fcd390 100644
--- a/ast.c
+++ b/ast.c
@@ -600,11 +600,11 @@ node_children(rb_ast_t *ast, const NODE *node)
         }
       case NODE_SCOPE:
         {
-            ID *tbl = node->nd_tbl;
-            int i, size = tbl ? (int)*tbl++ : 0;
+            rb_ast_id_table_t *tbl = node->nd_tbl;
+            int i, size = tbl ? tbl->size : 0;
             VALUE locals = rb_ary_new_capa(size);
             for (i = 0; i < size; i++) {
-                rb_ary_push(locals, var_name(tbl[i]));
+                rb_ary_push(locals, var_name(tbl->ids[i]));
             }
             return rb_ary_new_from_args(3, locals, NEW_CHILD(ast, node->nd_args), NEW_CHILD(ast, node->nd_body));
         }
diff --git a/common.mk b/common.mk
index 7ba32ac6e8..6b7378eeb6 100644
--- a/common.mk
+++ b/common.mk
@@ -7937,6 +7937,7 @@ localeinit.$(OBJEXT): {$(VPATH)}st.h
 localeinit.$(OBJEXT): {$(VPATH)}subst.h
 main.$(OBJEXT): $(hdrdir)/ruby.h
 main.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+main.$(OBJEXT): $(top_srcdir)/internal/compilers.h
 main.$(OBJEXT): {$(VPATH)}assert.h
 main.$(OBJEXT): {$(VPATH)}backward.h
 main.$(OBJEXT): {$(VPATH)}backward/2/assume.h
@@ -8463,6 +8464,7 @@ math.$(OBJEXT): {$(VPATH)}missing.h
 math.$(OBJEXT): {$(VPATH)}st.h
 math.$(OBJEXT): {$(VPATH)}subst.h
 memory_view.$(OBJEXT): $(hdrdir)/ruby/ruby.h
+memory_view.$(OBJEXT): $(top_srcdir)/internal/compilers.h
 memory_view.$(OBJEXT): $(top_srcdir)/internal/hash.h
 memory_view.$(OBJEXT): $(top_srcdir)/internal/variable.h
 memory_view.$(OBJEXT): {$(VPATH)}assert.h
diff --git a/compile.c b/compile.c
index a6505f82d6..d3cb079562 100644
--- a/compile.c
+++ b/compile.c
@@ -482,7 +482,7 @@ static int iseq_setup_insn(rb_iseq_t *iseq, LINK_ANCHOR *const anchor);
 static int iseq_optimize(rb_iseq_t *iseq, LINK_ANCHOR *const anchor);
 static int iseq_insns_unification(rb_iseq_t *iseq, LINK_ANCHOR *const anchor);
 
-static int iseq_set_local_table(rb_iseq_t *iseq, const ID *tbl);
+static int iseq_set_local_table(rb_iseq_t *iseq, const rb_ast_id_table_t *tbl);
 static int iseq_set_exception_local_table(rb_iseq_t *iseq);
 static int iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const anchor, const NODE *const node);
 
@@ -1946,21 +1946,13 @@ iseq_set_arguments(rb_iseq_t *iseq, LINK_ANCHOR *const optargs, const NODE *cons
 }
 
 static int
-iseq_set_local_table(rb_iseq_t *iseq, const ID *tbl)
+iseq_set_local_table(rb_iseq_t *iseq, const rb_ast_id_table_t *tbl)
 {
-    unsigned int size;
-
-    if (tbl) {
-	size = (unsigned int)*tbl;
-	tbl++;
-    }
-    else {
-	size = 0;
-    }
+    unsigned int size = tbl ? tbl->size : 0;
 
     if (size > 0) {
 	ID *ids = (ID *)ALLOC_N(ID, size);
-	MEMCPY(ids, tbl, ID, size);
+	MEMCPY(ids, tbl->ids, ID, size);
 	iseq->body->local_table = ids;
     }
     iseq->body->local_table_size = size;
@@ -7908,17 +7900,20 @@ compile_builtin_mandatory_only_method(rb_iseq_t *iseq, const NODE *node, const N
     // local table without non-mandatory parameters
     const int skip_local_size = iseq->body->param.size - iseq->body->param.lead_num;
     const int table_size = iseq->body->local_table_size - skip_local_size;
-    ID *tbl = ALLOCA_N(ID, table_size + 1);
-    tbl[0] = table_size;
+
+    VALUE idtmp = 0;
+    rb_ast_id_table_t *tbl = ALLOCV(idtmp, sizeof(rb_ast_id_table_t) + table_size * sizeof(ID));
+    tbl->size = table_size;
+
     int i;
 
     // lead parameters
     for (i=0; i<iseq->body->param.lead_num; i++) {
-        tbl[i+1] = iseq->body->local_table[i];
+        tbl->ids[i] = iseq->body->local_table[i];
     }
     // local variables
     for (; i<table_size; i++) {
-        tbl[i+1] = iseq->body->local_table[i + skip_local_size];
+        tbl->ids[i] = iseq->body->local_table[i + skip_local_size];
     }
 
     NODE scope_node;
@@ -7939,6 +7934,7 @@ compile_builtin_mandatory_only_method(rb_iseq_t *iseq, const NODE *node, const N
                            ISEQ_TYPE_METHOD, ISEQ_COMPILE_DATA(iseq)->option);
 
     GET_VM()->builtin_inline_index = prev_inline_index;
+    ALLOCV_END(idtmp);
     return COMPILE_OK;
 }
 
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)
 {
-    unsigned int size = (unsigned int)*buf;
-    buf[size + 1] = (ID)ast->node_buffer->local_tables;
-    ast->node_buffer->local_tables = buf;
+    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)
+{
+    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
diff --git a/node.h b/node.h
index 8450455624..bd1c9d1fbf 100644
--- a/node.h
+++ b/node.h
@@ -11,6 +11,8 @@
 
 **********************************************************************/
 
+#include "internal/compilers.h"
+
 #if defined(__cplusplus)
 extern "C" {
 #if 0
@@ -146,13 +148,18 @@ code_loc_gen(const rb_code_location_t *loc1, const rb_code_location_t *loc2)
     return loc;
 }
 
+typedef struct rb_ast_id_table {
+    int size;
+    ID ids[FLEX_ARY_LEN];
+} rb_ast_id_table_t;
+
 typedef struct RNode {
     VALUE flags;
     union {
 	struct RNode *node;
 	ID id;
 	VALUE value;
-	ID *tbl;
+	rb_ast_id_table_t *tbl;
     } u1;
     union {
 	struct RNode *node;
@@ -411,13 +418,14 @@ typedef struct rb_ast_struct {
 rb_ast_t *rb_ast_new(void);
 void rb_ast_mark(rb_ast_t*);
 void rb_ast_update_references(rb_ast_t*);
-void rb_ast_add_local_table(rb_ast_t*, ID *buf);
 void rb_ast_dispose(rb_ast_t*);
 void rb_ast_free(rb_ast_t*);
 size_t rb_ast_memsize(const rb_ast_t*);
 void rb_ast_add_mark_object(rb_ast_t*, VALUE);
 NODE *rb_ast_newnode(rb_ast_t*, enum node_type type);
 void rb_ast_delete_node(rb_ast_t*, NODE *n);
+rb_ast_id_table_t *rb_ast_new_local_table(rb_ast_t*, int);
+rb_ast_id_table_t *rb_ast_resize_latest_local_table(rb_ast_t*, int);
 
 VALUE rb_parser_new(void);
 VALUE rb_parser_end_seen_p(VALUE);
diff --git a/parse.y b/parse.y
index b6498651bf..d386561f6a 100644
--- a/parse.y
+++ b/parse.y
@@ -574,7 +574,7 @@ static NODE *symbol_append(struct parser_params *p, NODE *symbols, NODE *symbol)
 
 static NODE *match_op(struct parser_params*,NODE*,NODE*,const YYLTYPE*,const YYLTYPE*);
 
-static ID  *local_tbl(struct parser_params*);
+static rb_ast_id_table_t *local_tbl(struct parser_params*);
 
 static VALUE reg_compile(struct parser_params*, VALUE, int);
 static void reg_fragment_setenc(struct parser_params*, VALUE, int);
@@ -3172,9 +3172,8 @@ primary		: literal
 			ID id = internal_id(p);
 			NODE *m = NEW_ARGS_AUX(0, 0, &NULL_LOC);
 			NODE *args, *scope, *internal_var = NEW_DVAR(id, &@2);
-			ID *tbl = ALLOC_N(ID, 3);
-			tbl[0] = 1 /* length of local var table */; tbl[1] = id /* internal id */;
-                        rb_ast_add_local_table(p->ast, tbl);
+                        rb_ast_id_table_t *tbl = rb_ast_new_local_table(p->ast, 1);
+			tbl->ids[0] = id; /* internal id */
 
 			switch (nd_type($2)) {
 			  case NODE_LASGN:
@@ -12585,38 +12584,36 @@ local_pop(struct parser_params *p)
 }
 
 #ifndef RIPPER
-static ID*
+static rb_ast_id_table_t *
 local_tbl(struct parser_params *p)
 {
     int cnt_args = vtable_size(p->lvtbl->args);
     int cnt_vars = vtable_size(p->lvtbl->vars);
     int cnt = cnt_args + cnt_vars;
     int i, j;
-    ID *buf;
+    rb_ast_id_table_t *tbl;
 
     if (cnt <= 0) return 0;
-    buf = ALLOC_N(ID, cnt + 2);
-    MEMCPY(buf+1, p->lvtbl->args->tbl, ID, cnt_args);
+    tbl = rb_ast_new_local_table(p->ast, cnt);
+    MEMCPY(tbl->ids, p->lvtbl->args->tbl, ID, cnt_args);
     /* remove IDs duplicated to warn shadowing */
-    for (i = 0, j = cnt_args+1; i < cnt_vars; ++i) {
+    for (i = 0, j = cnt_args; i < cnt_vars; ++i) {
 	ID id = p->lvtbl->vars->tbl[i];
 	if (!vtable_included(p->lvtbl->args, id)) {
-	    buf[j++] = id;
+	    tbl->ids[j++] = id;
 	}
     }
-    if (--j < cnt) {
-	REALLOC_N(buf, ID, (cnt = j) + 2);
+    if (j < cnt) {
+        tbl = rb_ast_resize_latest_local_table(p->ast, j);
     }
-    buf[0] = cnt;
-    rb_ast_add_local_table(p->ast, buf);
 
-    return buf;
+    return tbl;
 }
 
 static NODE*
 node_newnode_with_locals(struct parser_params *p, enum node_type type, VALUE a1, VALUE a2, const rb_code_location_t *loc)
 {
-    ID *a0;
+    rb_ast_id_table_t *a0;
     NODE *n;
 
     a0 = local_tbl(p);
diff --git a/vm.c b/vm.c
index 5941329c4e..53f16275c3 100644
--- a/vm.c
+++ b/vm.c
@@ -1256,18 +1256,17 @@ rb_binding_add_dynavars(VALUE bindval, rb_binding_t *bind, int dyncount, const I
     const rb_iseq_t *base_iseq, *iseq;
     rb_ast_body_t ast;
     NODE tmp_node;
-    ID minibuf[4], *dyns = minibuf;
-    VALUE idtmp = 0;
 
     if (dyncount < 0) return 0;
 
     base_block = &bind->block;
     base_iseq = vm_block_iseq(base_block);
 
-    if (dyncount >= numberof(minibuf)) dyns = ALLOCV_N(ID, idtmp, dyncount + 1);
+    VALUE idtmp = 0;
+    rb_ast_id_table_t *dyns = ALLOCV(idtmp, sizeof(rb_ast_id_table_t) + dyncount * sizeof(ID));
+    dyns->size = dyncount;
+    MEMCPY(dyns->ids, dynvars, ID, dyncount);
 
-    dyns[0] = dyncount;
-    MEMCPY(dyns + 1, dynvars, ID, dyncount);
     rb_node_init(&tmp_node, NODE_SCOPE, (VALUE)dyns, 0, 0);
     ast.root = &tmp_node;
     ast.compile_option = 0;