Class initializers

common.h

@@ -5,11 +5,11 @@
 #include <stddef.h>
 #include <stdint.h>
 
-// #define DEBUG_PRINT_CODE
-// #define DEBUG_TRACE_EXECUTION
-//
-// #define DEBUG_STRESS_GC
-// #define DEBUG_LOG_GC
+#define DEBUG_PRINT_CODE
+#define DEBUG_TRACE_EXECUTION
+
+#define DEBUG_STRESS_GC
+#define DEBUG_LOG_GC
 
 #define UINT8_COUNT (UINT8_MAX + 1)
 

compiler.c

@@ -54,6 +54,7 @@ typedef struct {
 typedef enum {
   TYPE_FUNCTION,
   TYPE_METHOD,
+  TYPE_INITIALIZER,
   TYPE_SCRIPT
 } FunctionType;
 
@@ -162,7 +163,11 @@ static int emitJump(uint8_t instruction) {
 }
 
 static void emitReturn() {
-  emitByte(OP_NIL);
+  if (current->type == TYPE_INITIALIZER) {
+    emitBytes(OP_GET_LOCAL, 0);
+  } else {
+    emitByte(OP_NIL);
+  }
   emitByte(OP_RETURN);
 }
 
@@ -469,6 +474,9 @@ static void method() {
   uint8_t constant = identifierConstant(&parser.previous);
 
   FunctionType type = TYPE_METHOD;
+  if (parser.previous.length == 4 && memcmp(parser.previous.start, "init", 4) == 0) {
+    type = TYPE_INITIALIZER;
+  }
   function(type);
   emitBytes(OP_METHOD, constant);
 }

memory.c

@@ -192,6 +192,7 @@ static void markRoots() {
 
   markTable(&vm.globals);
   markCompilerRoots();
+  markObject((Obj*)vm.initString);
 }
 
 static void traceReferences() {

vm.c

@@ -66,10 +66,14 @@ void initVM() {
   initTable(&vm.globals);
   initTable(&vm.strings);
 
+  vm.initString = NULL;
+  vm.initString = copyString("init", 4);
+
   defineNative("clock", clockNative);
 }
 
 void freeVM() {
+  vm.initString = NULL;
   freeTable(&vm.globals);
   freeTable(&vm.strings);
   freeObjects();
@@ -119,6 +123,12 @@ static bool callValue(Value callee, int argCount) {
       case OBJ_CLASS: {
         ObjClass* klass = AS_CLASS(callee);
         vm.stackTop[-argCount-1] = OBJ_VAL(newInstance(klass));
+        Value initializer;
+        if (tableGet(&klass->methods, vm.initString, &initializer)) {
+          return call(AS_CLOSURE(initializer), argCount);
+        } else if (argCount != 0) {
+          runtimeError("Expected 0 arguments but got %d.", argCount);
+        }
         return true;
       }
       case OBJ_CLOSURE:

vm.h

@@ -30,6 +30,7 @@ typedef struct {
   Obj** grayStack;
 
   Table strings;
+  ObjString* initString;
   Table globals;
 
   ObjUpvalue* openUpvalues;