Allow defs to reference other defs

asm.js

@@ -112,6 +112,7 @@ const Action = Object.freeze({
     DATA:   11,
     ALIGN:  12,
     DEF:    13,
+    LABEL:  14,
 });
 
 const types = {
@@ -224,6 +225,8 @@ class Parser {
             this.state = state;
             return;
         }
+        if (token.endsWith(":"))
+            return { type: Action.LABEL, name: token.slice(0, -1) };
         const code = this.translate_code(token);
         if (code)
             return { type: Action.APPEND, code };
@@ -497,7 +500,7 @@ class Parser {
             this.state = State.TOP;
             return;
         }
-        const action = { type: Action.DATA, size: 2 };
+        const action = { type: Action.DATA, size: 4 };
         const value = this.integer(token);
         if (value == null) {
             action.symbol = token;
@@ -557,18 +560,15 @@ class Parser {
             this.state = State.TOP;
             return;
         }
-        const value = this.integer(token);
-        if (value == null) {
-            console.error(
-                `ERROR: Unexpected token ${token}, expected value`);
-            this.def_name = undefined;
-            this.state = State.TOP;
-            return;
-        }
         const action = {
             type: Action.DEF,
-            def: { name: this.def_name, value },
+            def: { name: this.def_name },
         };
+        const value = this.integer(token);
+        if (value != null)
+            action.def.value = value;
+        else
+            action.def.symbol = token;
         this.def_name = undefined;
         this.state = State.TOP;
         return action;
@@ -630,6 +630,7 @@ export class Assembler {
             [Action.DATA]:   (action) => this.action_data(action),
             [Action.ALIGN]:  (action) => this.action_align(action),
             [Action.DEF]:    (action) => this.action_def(action),
+            [Action.LABEL]:  (action) => this.action_label(action),
         };
 
         this.exports = [];
@@ -738,7 +739,13 @@ export class Assembler {
     }
 
     action_def(action) {
-        this.defs[action.def.name] = action.def.value;
+        const value = action.def.value
+              ?? this.lookup_def(action.def.symbol);
+        this.defs[action.def.name] = value;
+    }
+
+    action_label(action) {
+        this.defs[action.name] = this.pos.addr;
     }
 
 	push(chunk) {