diff --git a/src/c/interpreter.d b/src/c/interpreter.d
index cb2074e78..52b1fbef0 100644
--- a/src/c/interpreter.d
+++ b/src/c/interpreter.d
@@ -121,9 +121,34 @@ VEclose_around_arg_type()
  *      sym_macro = ( si::symbol-macro macro_function[bytecodes] . macro_name )
  */
 
-#define bind_var(env, var, val)   CONS(CONS(var, val), (env))
-#define bind_function(env, fun)   CONS(fun, (env))
-#define bind_frame(env, id, name) CONS(CONS(id, name), (env))
+#define bind_lcl(env, entry)   push_lcl(&env, entry)
+#define tack_lcl(env, entries) foot_lcl(&env, entries)
+
+#define bind_var(env, var, val)   bind_lcl(env, CONS(var, val))
+#define bind_function(env, fun)   bind_lcl(env, fun)
+#define bind_frame(env, id, name) bind_lcl(env, CONS(id, name))
+
+#define unbind_lcl(env, n) drop_lcl(&env, n)
+#define tangle_lcl(stack) (stack)
+#define unwind_lcl(stack, where) (stack = where)
+
+static void
+push_lcl(cl_object *stack, cl_object new)
+{
+  *stack = ecl_cons(new, *stack);
+}
+
+static void
+foot_lcl(cl_object *stack, cl_object list)
+{
+  *stack = ecl_append(list, *stack);
+}
+
+static void
+drop_lcl(cl_object *stack, cl_fixnum n)
+{
+  while (n--) *stack = ECL_CONS_CDR(*stack);
+}
 
 static cl_object
 ecl_lcl_env_get_record(cl_object env, int s)
@@ -697,10 +722,10 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
       for(idx = 0; idx<nfun; idx++) {
         GET_DATA(fun, vector, data);
         fun = ecl_close_around(fun, lcl_env, lex_env);
-        fun_env = bind_function(fun_env, fun);
+        fun_env = CONS(fun, fun_env);
       }
       /* Update the environment with new functions. */
-      lcl_env = ecl_append(fun_env, lcl_env);
+      tack_lcl(lcl_env, fun_env);
       THREAD_NEXT;
     }
     /* OP_LABELS    nfun{arg}
@@ -714,26 +739,22 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
        the functions "fun1" ... "funn".
     */
     CASE(OP_LABELS); {
-      cl_index nfun;
+      cl_index idx, nfun;
+      cl_object fun_env=ECL_NIL, fun;
       GET_OPARG(nfun, vector);
-      /* Build up a new environment with all functions */
-      {
-        cl_index i = nfun;
-        do {
-          cl_object f;
-          GET_DATA(f, vector, data);
-          f = close_around_self(f);
-          lcl_env = bind_function(lcl_env, f);
-        } while (--i);
+      /* Create closures. */
+      for(idx = 0; idx<nfun; idx++) {
+        GET_DATA(fun, vector, data);
+        fun = close_around_self(fun);
+        fun_env = CONS(fun, fun_env);
       }
+      /* Update the environment with new functions. */
+      tack_lcl(lcl_env, fun_env);
       /* Update the closures so that all functions can call each other */
-      {
-        cl_object l = lcl_env;
-        do {
-          close_around_self_fixup(ECL_CONS_CAR(l), lcl_env, lex_env);
-          l = ECL_CONS_CDR(l);
-        } while (--nfun);
-      }
+      loop_for_on_unsafe(fun_env) {
+        fun = ECL_CONS_CAR(fun_env);
+        close_around_self_fixup(fun, lcl_env, lex_env);
+      } end_loop_for_on_unsafe(fun_env);
       THREAD_NEXT;
     }
     /* OP_LFUNCTION index{fixnum} ; local
@@ -902,8 +923,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     CASE(OP_UNBIND); {
       cl_oparg n;
       GET_OPARG(n, vector);
-      while (n--)
-        lcl_env = ECL_CONS_CDR(lcl_env);
+      unbind_lcl(lcl_env, n);
       THREAD_NEXT;
     }
     /* OP_UNBINDS   n{arg}
@@ -928,13 +948,13 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     CASE(OP_BIND); {
       cl_object var_name;
       GET_DATA(var_name, vector, data);
-      lcl_env = bind_var(lcl_env, var_name, reg0);
+      bind_var(lcl_env, var_name, reg0);
       THREAD_NEXT;
     }
     CASE(OP_PBIND); {
       cl_object var_name;
       GET_DATA(var_name, vector, data);
-      lcl_env = bind_var(lcl_env, var_name, ECL_STACK_POP_UNSAFE(the_env));
+      bind_var(lcl_env, var_name, ECL_STACK_POP_UNSAFE(the_env));
       THREAD_NEXT;
     }
     CASE(OP_VBIND); {
@@ -942,8 +962,8 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
       cl_object var_name;
       GET_OPARG(n, vector);
       GET_DATA(var_name, vector, data);
-      lcl_env = bind_var(lcl_env, var_name,
-                         (n < the_env->nvalues) ? the_env->values[n] : ECL_NIL);
+      bind_var(lcl_env, var_name,
+               (n < the_env->nvalues) ? the_env->values[n] : ECL_NIL);
       THREAD_NEXT;
     }
     CASE(OP_BINDS); {
@@ -1070,24 +1090,24 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     CASE(OP_BLOCK); {
       GET_DATA(reg0, vector, data);
       reg1 = ecl_make_fixnum(the_env->frame_id++);
-      lcl_env = bind_frame(lcl_env, reg1, reg0);
+      bind_frame(lcl_env, reg1, reg0);
       THREAD_NEXT;
     }
     CASE(OP_DO); {
       reg0 = ECL_NIL;
       reg1 = ecl_make_fixnum(the_env->frame_id++);
-      lcl_env = bind_frame(lcl_env, reg1, reg0);
+      bind_frame(lcl_env, reg1, reg0);
       THREAD_NEXT;
     }
     CASE(OP_CATCH); {
       reg1 = reg0;
-      lcl_env = bind_frame(lcl_env, reg1, reg0);
+      bind_frame(lcl_env, reg1, reg0);
       THREAD_NEXT;
     }
     CASE(OP_FRAME); {
       cl_opcode *exit;
       GET_LABEL(exit, vector);
-      ECL_STACK_PUSH(the_env, lcl_env);
+      ECL_STACK_PUSH(the_env, tangle_lcl(lcl_env));
       ECL_STACK_PUSH(the_env, (cl_object)exit);
       ecl_frs_push(the_env,reg1);
       if (__ecl_frs_push_result == 0) {
@@ -1095,7 +1115,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
       } else {
         reg0 = the_env->values[0];
         vector = (cl_opcode *)ECL_STACK_REF(the_env,-1); /* FIXME! */
-        lcl_env = ECL_STACK_REF(the_env,-2);
+        unwind_lcl(lcl_env, ECL_STACK_REF(the_env, -2));
         goto DO_EXIT_FRAME;
       }
     }
@@ -1115,7 +1135,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     CASE(OP_TAGBODY); {
       int n;
       GET_OPARG(n, vector);
-      ECL_STACK_PUSH(the_env, lcl_env);
+      ECL_STACK_PUSH(the_env, tangle_lcl(lcl_env));
       ECL_STACK_PUSH(the_env, (cl_object)vector); /* FIXME! */
       vector += n * OPARG_SIZE;
       ecl_frs_push(the_env,reg1);
@@ -1124,7 +1144,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
            ranges from 0 to ntags-1, depending on the tag. These numbers are
            indices into the jump table and are computed at compile time. */
         cl_opcode *table = (cl_opcode *)ECL_STACK_REF(the_env,-1);
-        lcl_env = ECL_STACK_REF(the_env,-2);
+        unwind_lcl(lcl_env, ECL_STACK_REF(the_env,-2));
         table = table + ecl_fixnum(the_env->values[0]) * OPARG_SIZE;
         vector = table + *(cl_oparg *)table;
       }
@@ -1137,7 +1157,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     DO_EXIT_FRAME:
       ecl_frs_pop(the_env);
       ECL_STACK_POP_N_UNSAFE(the_env, 2);
-      lcl_env = ECL_CONS_CDR(lcl_env);
+      unbind_lcl(lcl_env, 1);
       THREAD_NEXT;
     }
     CASE(OP_NIL); {
@@ -1241,13 +1261,13 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
     CASE(OP_PROTECT); {
       cl_opcode *exit;
       GET_LABEL(exit, vector);
-      ECL_STACK_PUSH(the_env, lcl_env);
+      ECL_STACK_PUSH(the_env, tangle_lcl(lcl_env));
       ECL_STACK_PUSH(the_env, (cl_object)exit);
       ecl_frs_push(the_env,ECL_PROTECT_TAG);
       if (__ecl_frs_push_result != 0) {
         ecl_frs_pop(the_env);
         vector = (cl_opcode *)ECL_STACK_POP_UNSAFE(the_env);
-        lcl_env = ECL_STACK_POP_UNSAFE(the_env);
+        unwind_lcl(lcl_env, ECL_STACK_POP_UNSAFE(the_env));
         reg0 = the_env->values[0];
         ECL_STACK_PUSH(the_env, ecl_make_fixnum(the_env->nlj_fr - the_env->frs_top));
         goto PUSH_VALUES;
@@ -1258,7 +1278,7 @@ ecl_interpret(cl_object frame, cl_object closure, cl_object bytecodes)
       ecl_bds_unwind(the_env, the_env->frs_top->frs_bds_top_index);
       ecl_frs_pop(the_env);
       (void)ECL_STACK_POP_UNSAFE(the_env);
-      lcl_env = ECL_STACK_POP_UNSAFE(the_env);
+      unwind_lcl(lcl_env, ECL_STACK_POP_UNSAFE(the_env));
       ECL_STACK_PUSH(the_env, ecl_make_fixnum(1));
       goto PUSH_VALUES;
     }