fixed 'return' handling with 'yield' in 'for of' or with finally blocks (gihub ticket #166)

quickjs-opcode.h

@@ -182,6 +182,7 @@ DEF(           goto, 5, 0, 0, label) /* must come after if_true */
 DEF(          catch, 5, 0, 1, label)
 DEF(          gosub, 5, 0, 0, label) /* used to execute the finally block */
 DEF(            ret, 1, 1, 0, none) /* used to return from the finally block */
+DEF(      nip_catch, 1, 2, 1, none) /* catch ... a -> a */
 
 DEF(      to_object, 1, 1, 1, none)
 //DEF(      to_string, 1, 1, 1, none)
@@ -208,7 +209,6 @@ DEF(    for_of_next, 2, 3, 5, u8)
 DEF(iterator_check_object, 1, 1, 1, none)
 DEF(iterator_get_value_done, 1, 1, 2, none)
 DEF( iterator_close, 1, 3, 0, none)
-DEF(iterator_close_return, 1, 4, 4, none)
 DEF(  iterator_next, 1, 4, 4, none)
 DEF(  iterator_call, 2, 4, 5, u8)
 DEF(  initial_yield, 1, 0, 0, none)

quickjs.c

@@ -87,6 +87,7 @@
    8: dump stdlib functions
   16: dump bytecode in hex
   32: dump line number table
+  64: dump compute_stack_size
  */
 //#define DUMP_BYTECODE  (1)
 /* dump the occurence of the automatic GC */
@@ -17091,26 +17092,21 @@ static JSValue JS_CallInternal(JSContext *caller_ctx, JSValueConst func_obj,
             }
             sp--;
             BREAK;
-        CASE(OP_iterator_close_return):
+        CASE(OP_nip_catch):
             {
                 JSValue ret_val;
-                /* iter_obj next catch_offset ... ret_val ->
+                /* catch_offset ... ret_val -> ret_eval */
-                   ret_eval iter_obj next catch_offset */
                 ret_val = *--sp;
                 while (sp > stack_buf &&
                        JS_VALUE_GET_TAG(sp[-1]) != JS_TAG_CATCH_OFFSET) {
                     JS_FreeValue(ctx, *--sp);
                 }
-                if (unlikely(sp < stack_buf + 3)) {
+                if (unlikely(sp == stack_buf)) {
-                    JS_ThrowInternalError(ctx, "iterator_close_return");
+                    JS_ThrowInternalError(ctx, "nip_catch");
                     JS_FreeValue(ctx, ret_val);
                     goto exception;
                 }
-                sp[0] = sp[-1];
+                sp[-1] = ret_val;
-                sp[-1] = sp[-2];
-                sp[-2] = sp[-3];
-                sp[-3] = ret_val;
-                sp++;
             }
             BREAK;
 
@@ -25438,7 +25434,6 @@ static __exception int emit_break(JSParseState *s, JSAtom name, int is_cont)
 static void emit_return(JSParseState *s, BOOL hasval)
 {
     BlockEnv *top;
-    int drop_count;
 
     if (s->cur_func->func_kind != JS_FUNC_NORMAL) {
         if (!hasval) {
@@ -25452,26 +25447,24 @@ static void emit_return(JSParseState *s, BOOL hasval)
         }
     }
     
-    drop_count = 0;
     top = s->cur_func->top_break;
     while (top != NULL) {
-        /* XXX: emit the appropriate OP_leave_scope opcodes? Probably not
+        if (top->has_iterator || top->label_finally != -1) {
-           required as all local variables will be closed upon returning
-           from JS_CallInternal, but not in the same order. */
-        if (top->has_iterator) {
-            /* with 'yield', the exact number of OP_drop to emit is
-               unknown, so we use a specific operation to look for
-               the catch offset */
             if (!hasval) {
                 emit_op(s, OP_undefined);
                 hasval = TRUE;
             }
-            emit_op(s, OP_iterator_close_return);
+            /* Remove the stack elements up to and including the catch
+               offset. When 'yield' is used in an expression we have
+               no easy way to count them, so we use this specific
+               instruction instead. */
+            emit_op(s, OP_nip_catch);
+            /* stack: iter_obj next ret_val */
+            if (top->has_iterator) {
                 if (s->cur_func->func_kind == JS_FUNC_ASYNC_GENERATOR) {
                     int label_next, label_next2;
-
+                    emit_op(s, OP_nip); /* next */
-                emit_op(s, OP_drop); /* catch offset */
+                    emit_op(s, OP_swap);
-                emit_op(s, OP_drop); /* next */
                     emit_op(s, OP_get_field2);
                     emit_atom(s, JS_ATOM_return);
                     /* stack: iter_obj return_func */
@@ -25488,24 +25481,15 @@ static void emit_return(JSParseState *s, BOOL hasval)
                     emit_label(s, label_next2);
                     emit_op(s, OP_drop);
                 } else {
+                    emit_op(s, OP_rot3r);
+                    emit_op(s, OP_undefined); /* dummy catch offset */
                     emit_op(s, OP_iterator_close);
                 }
-            drop_count = -3;
+            } else {
-        }
+                /* execute the "finally" block */
-        drop_count += top->drop_count;
-        if (top->label_finally != -1) {
-            while(drop_count) {
-                /* must keep the stack top if hasval */
-                emit_op(s, hasval ? OP_nip : OP_drop);
-                drop_count--;
-            }
-            if (!hasval) {
-                /* must push return value to keep same stack size */
-                emit_op(s, OP_undefined);
-                hasval = TRUE;
-            }
                 emit_goto(s, OP_gosub, top->label_finally);
             }
+        }
         top = top->prev;
     }
     if (s->cur_func->is_derived_class_constructor) {
@@ -31901,6 +31885,7 @@ typedef struct StackSizeState {
     int bc_len;
     int stack_len_max;
     uint16_t *stack_level_tab;
+    int32_t *catch_pos_tab;
     int *pc_stack;
     int pc_stack_len;
     int pc_stack_size;
@@ -31908,7 +31893,7 @@ typedef struct StackSizeState {
 
 /* 'op' is only used for error indication */
 static __exception int ss_check(JSContext *ctx, StackSizeState *s,
-                                int pos, int op, int stack_len)
+                                int pos, int op, int stack_len, int catch_pos)
 {
     if ((unsigned)pos >= s->bc_len) {
         JS_ThrowInternalError(ctx, "bytecode buffer overflow (op=%d, pc=%d)", op, pos);
@@ -31927,6 +31912,10 @@ static __exception int ss_check(JSContext *ctx, StackSizeState *s,
             JS_ThrowInternalError(ctx, "inconsistent stack size: %d %d (pc=%d)",
                                   s->stack_level_tab[pos], stack_len, pos);
             return -1;
+        } else if (s->catch_pos_tab[pos] != catch_pos) {
+            JS_ThrowInternalError(ctx, "inconsistent catch position: %d %d (pc=%d)",
+                                  s->catch_pos_tab[pos], catch_pos, pos);
+            return -1;
         } else {
             return 0;
         }
@@ -31934,6 +31923,7 @@ static __exception int ss_check(JSContext *ctx, StackSizeState *s,
 
     /* mark as explored and store the stack size */
     s->stack_level_tab[pos] = stack_len;
+    s->catch_pos_tab[pos] = catch_pos;
     
     /* queue the new PC to explore */
     if (js_resize_array(ctx, (void **)&s->pc_stack, sizeof(s->pc_stack[0]),
@@ -31948,7 +31938,7 @@ static __exception int compute_stack_size(JSContext *ctx,
                                           int *pstack_size)
 {
     StackSizeState s_s, *s = &s_s;
-    int i, diff, n_pop, pos_next, stack_len, pos, op;
+    int i, diff, n_pop, pos_next, stack_len, pos, op, catch_pos, catch_level;
     const JSOpCode *oi;
     const uint8_t *bc_buf;
 
@@ -31961,24 +31951,33 @@ static __exception int compute_stack_size(JSContext *ctx,
         return -1;
     for(i = 0; i < s->bc_len; i++)
         s->stack_level_tab[i] = 0xffff;
-    s->stack_len_max = 0;
     s->pc_stack = NULL;
+    s->catch_pos_tab = js_malloc(ctx, sizeof(s->catch_pos_tab[0]) *
+                                   s->bc_len);
+    if (!s->catch_pos_tab)
+        goto fail;
+
+    s->stack_len_max = 0;
     s->pc_stack_len = 0;
     s->pc_stack_size = 0;
 
     /* breadth-first graph exploration */
-    if (ss_check(ctx, s, 0, OP_invalid, 0))
+    if (ss_check(ctx, s, 0, OP_invalid, 0, -1))
         goto fail;
 
     while (s->pc_stack_len > 0) {
         pos = s->pc_stack[--s->pc_stack_len];
         stack_len = s->stack_level_tab[pos];
+        catch_pos = s->catch_pos_tab[pos];
         op = bc_buf[pos];
         if (op == 0 || op >= OP_COUNT) {
             JS_ThrowInternalError(ctx, "invalid opcode (op=%d, pc=%d)", op, pos);
             goto fail;
         }
         oi = &short_opcode_info(op);
+#if defined(DUMP_BYTECODE) && (DUMP_BYTECODE & 64)
+        printf("%5d: %10s %5d %5d\n", pos, oi->name, stack_len, catch_pos);
+#endif
         pos_next = pos + oi->size;
         if (pos_next > s->bc_len) {
             JS_ThrowInternalError(ctx, "bytecode buffer overflow (op=%d, pc=%d)", op, pos);
@@ -32034,55 +32033,104 @@ static __exception int compute_stack_size(JSContext *ctx,
         case OP_if_true8:
         case OP_if_false8:
             diff = (int8_t)bc_buf[pos + 1];
-            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len))
+            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len, catch_pos))
                 goto fail;
             break;
 #endif
         case OP_if_true:
         case OP_if_false:
-        case OP_catch:
             diff = get_u32(bc_buf + pos + 1);
-            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len))
+            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len, catch_pos))
                 goto fail;
             break;
         case OP_gosub:
             diff = get_u32(bc_buf + pos + 1);
-            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len + 1))
+            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len + 1, catch_pos))
                 goto fail;
             break;
         case OP_with_get_var:
         case OP_with_delete_var:
             diff = get_u32(bc_buf + pos + 5);
-            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len + 1))
+            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len + 1, catch_pos))
                 goto fail;
             break;
         case OP_with_make_ref:
         case OP_with_get_ref:
         case OP_with_get_ref_undef:
             diff = get_u32(bc_buf + pos + 5);
-            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len + 2))
+            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len + 2, catch_pos))
                 goto fail;
             break;
         case OP_with_put_var:
             diff = get_u32(bc_buf + pos + 5);
-            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len - 1))
+            if (ss_check(ctx, s, pos + 5 + diff, op, stack_len - 1, catch_pos))
                 goto fail;
             break;
-
+        case OP_catch:
+            diff = get_u32(bc_buf + pos + 1);
+            if (ss_check(ctx, s, pos + 1 + diff, op, stack_len, catch_pos))
+                goto fail;
+            catch_pos = pos;
+            break;
+        case OP_for_of_start:
+        case OP_for_await_of_start:
+            catch_pos = pos;
+            break;
+            /* we assume the catch offset entry is only removed with
+               some op codes */
+        case OP_drop:
+            catch_level = stack_len;
+            goto check_catch;
+        case OP_nip:
+            catch_level = stack_len - 1;
+            goto check_catch;
+        case OP_nip1:
+            catch_level = stack_len - 1;
+            goto check_catch;
+        case OP_iterator_close:
+            catch_level = stack_len + 2;
+        check_catch:
+            /* Note: for for_of_start/for_await_of_start we consider
+               the catch offset is on the first stack entry instead of
+               the thirst */
+            if (catch_pos >= 0) {
+                int level;
+                level = s->stack_level_tab[catch_pos];
+                if (bc_buf[catch_pos] != OP_catch)
+                    level++; /* for_of_start, for_wait_of_start */
+                /* catch_level = stack_level before op_catch is executed ? */
+                if (catch_level == level) {
+                    catch_pos = s->catch_pos_tab[catch_pos];
+                }
+            }
+            break;
+        case OP_nip_catch:
+            if (catch_pos < 0) {
+                JS_ThrowInternalError(ctx, "nip_catch: no catch op (pc=%d)", pos);
+                goto fail;
+            }
+            stack_len = s->stack_level_tab[catch_pos];
+            if (bc_buf[catch_pos] != OP_catch)
+                stack_len++; /* for_of_start, for_wait_of_start */
+            stack_len++; /* no stack overflow is possible by construction */
+            catch_pos = s->catch_pos_tab[catch_pos];
+            break;
         default:
             break;
         }
-        if (ss_check(ctx, s, pos_next, op, stack_len))
+        if (ss_check(ctx, s, pos_next, op, stack_len, catch_pos))
             goto fail;
     done_insn: ;
     }
-    js_free(ctx, s->stack_level_tab);
     js_free(ctx, s->pc_stack);
+    js_free(ctx, s->catch_pos_tab);
+    js_free(ctx, s->stack_level_tab);
     *pstack_size = s->stack_len_max;
     return 0;
  fail:
-    js_free(ctx, s->stack_level_tab);
     js_free(ctx, s->pc_stack);
+    js_free(ctx, s->catch_pos_tab);
+    js_free(ctx, s->stack_level_tab);
     *pstack_size = 0;
     return -1;
 }

tests/test_builtin.js

@@ -645,6 +645,18 @@ function test_generator()
         assert(ret, "ret_val");
         return 3;
     }
+    function *f3() {
+        var ret;
+        /* test stack consistency with nip_n to handle yield return +
+         * finally clause */
+        try {
+            ret = 2 + (yield 1);
+        } catch(e) {
+        } finally {
+            ret++;
+        }
+        return ret;
+    }
     var g, v;
     g = f();
     v = g.next();
@@ -665,6 +677,12 @@ function test_generator()
     assert(v.value === 3 && v.done === true);
     v = g.next();
     assert(v.value === undefined && v.done === true);
+
+    g = f3();
+    v = g.next();
+    assert(v.value === 1 && v.done === false);
+    v = g.next(3);
+    assert(v.value === 6 && v.done === true);
 }
 
 test();