From 410f30ef93aebab85238e470253aefdd5f0348c1 Mon Sep 17 00:00:00 2001
From: Tom Willemse
Date: Tue, 15 Mar 2022 00:39:11 -0700
Subject: Chapter 24.5

---
 clox/src/chunk.h    |  1 +
 clox/src/compiler.c | 27 +++++++++++++++++--
 clox/src/debug.c    |  2 ++
 clox/src/vm.c       | 78 +++++++++++++++++++++++++++++++++++++++++++----------
 4 files changed, 92 insertions(+), 16 deletions(-)

diff --git a/clox/src/chunk.h b/clox/src/chunk.h
index 2ec7a8d..37f5d6e 100644
--- a/clox/src/chunk.h
+++ b/clox/src/chunk.h
@@ -28,6 +28,7 @@ typedef enum {
   OP_JUMP,
   OP_JUMP_IF_FALSE,
   OP_LOOP,
+  OP_CALL,
   OP_RETURN,
 } OpCode;
 
diff --git a/clox/src/compiler.c b/clox/src/compiler.c
index bd835f2..ea40d7e 100644
--- a/clox/src/compiler.c
+++ b/clox/src/compiler.c
@@ -143,7 +143,10 @@ static int emitJump(uint8_t instruction) {
   return currentChunk()->count - 2;
 }
 
-static void emitReturn() { emitByte(OP_RETURN); }
+static void emitReturn() {
+  emitByte(OP_NIL);
+  emitByte(OP_RETURN);
+}
 
 static uint8_t makeConstant(Value value) {
   int constant = addConstant(currentChunk(), value);
@@ -269,6 +272,26 @@ static void binary(bool canAssign) {
   }
 }
 
+static uint8_t argumentList() {
+  uint8_t argCount = 0;
+  if (!check(TOKEN_RIGHT_PAREN)) {
+    do {
+      expression();
+      if (argCount == 255) {
+        error("Can't have more than 255 arguments.");
+      }
+      argCount++;
+    } while (match(TOKEN_COMMA));
+  }
+  consume(TOKEN_RIGHT_PAREN, "Expect ')' after arguments.");
+  return argCount;
+}
+
+static void call(bool canAssign) {
+  uint8_t argCount = argumentList();
+  emitBytes(OP_CALL, argCount);
+}
+
 static void literal(bool canAssign) {
   switch (parser.previous.type) {
   case TOKEN_FALSE:
@@ -571,7 +594,7 @@ static void grouping(bool canAssign) {
 }
 
 ParseRule rules[] = {
-    [TOKEN_LEFT_PAREN] = {grouping, NULL, PREC_NONE},
+    [TOKEN_LEFT_PAREN] = {grouping, call, PREC_CALL},
     [TOKEN_RIGHT_PAREN] = {NULL, NULL, PREC_NONE},
     [TOKEN_LEFT_BRACE] = {NULL, NULL, PREC_NONE},
     [TOKEN_RIGHT_BRACE] = {NULL, NULL, PREC_NONE},
diff --git a/clox/src/debug.c b/clox/src/debug.c
index 3f3c289..7ba728d 100644
--- a/clox/src/debug.c
+++ b/clox/src/debug.c
@@ -94,6 +94,8 @@ int disassembleInstruction(Chunk *chunk, int offset) {
     return jumpInstruction("OP_JUMP_IF_FALSE", 1, chunk, offset);
   case OP_LOOP:
     return jumpInstruction("OP_LOOP", -1, chunk, offset);
+  case OP_CALL:
+    return byteInstruction("OP_CALL", chunk, offset);
   case OP_RETURN:
     return simpleInstruction("OP_RETURN", offset);
   default:
diff --git a/clox/src/vm.c b/clox/src/vm.c
index 7dd79a3..0d8d638 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -23,10 +23,18 @@ static void runtimeError(const char *format, ...) {
   va_end(args);
   fputs("\n", stderr);
 
-  CallFrame *frame = &vm.frames[vm.frameCount - 1];
-  size_t instruction = frame->ip - frame->function->chunk.code - 1;
-  int line = frame->function->chunk.lines[instruction];
-  fprintf(stderr, "[line %d] in script\n", line);
+  for (int i = vm.frameCount; i >= 0; i--) {
+    CallFrame *frame = &vm.frames[i];
+    ObjFunction *function = frame->function;
+    size_t instruction = frame->ip - function->chunk.code - 1;
+    fprintf(stderr, "[line %d] in ", function->chunk.lines[instruction]);
+    if (function->name == NULL) {
+      fprintf(stderr, "script\n");
+    } else {
+      fprintf(stderr, "%s()\n", function->name->chars);
+    }
+  }
+
   resetStack();
 }
 
@@ -56,6 +64,38 @@ Value pop() {
 
 static Value peek(int distance) { return vm.stackTop[-1 - distance]; }
 
+static bool call(ObjFunction *function, int argCount) {
+  if (argCount != function->arity) {
+    runtimeError("Expected %d argumetns but got %d.", function->arity,
+                 argCount);
+    return false;
+  }
+
+  if (vm.frameCount == FRAMES_MAX) {
+    runtimeError("Stack overflow.");
+    return false;
+  }
+
+  CallFrame *frame = &vm.frames[vm.frameCount++];
+  frame->function = function;
+  frame->ip = function->chunk.code;
+  frame->slots = vm.stackTop - argCount - 1;
+  return true;
+}
+
+static bool callValue(Value callee, int argCount) {
+  if (IS_OBJ(callee)) {
+    switch (OBJ_TYPE(callee)) {
+    case OBJ_FUNCTION:
+      return call(AS_FUNCTION(callee), argCount);
+    default:
+      break;
+    }
+  }
+  runtimeError("Can only call functions && classes.");
+  return false;
+}
+
 static bool isFalsey(Value value) {
   return IS_NIL(value) || (IS_BOOL(value) && !AS_BOOL(value));
 }
@@ -226,13 +266,26 @@ static InterpretResult run() {
       frame->ip -= offset;
       break;
     }
+    case OP_CALL: {
+      int argCount = READ_BYTE();
+      if (!callValue(peek(argCount), argCount)) {
+        return INTERPRET_RUNTIME_ERROR;
+      }
+      frame = &vm.frames[vm.frameCount - 1];
+      break;
+    }
     case OP_RETURN: {
-      /* The book said to remove this, but when I do I get an infinite loop and
-         then a segfault because it keeps trying to add the constant 1 to the
-         stack. */
-      printValue(pop());
-      printf("\n");
-      return INTERPRET_OK;
+      Value result = pop();
+      vm.frameCount--;
+      if (vm.frameCount == 0) {
+        pop();
+        return INTERPRET_OK;
+      }
+
+      vm.stackTop = frame->slots;
+      push(result);
+      frame = &vm.frames[vm.frameCount - 1];
+      break;
     }
     }
   }
@@ -250,10 +303,7 @@ InterpretResult interpret(const char *source) {
     return INTERPRET_COMPILE_ERROR;
 
   push(OBJ_VAL(function));
-  CallFrame *frame = &vm.frames[vm.frameCount++];
-  frame->function = function;
-  frame->ip = function->chunk.code;
-  frame->slots = vm.stack;
+  call(function, 0);
 
   return run();
 }
-- 
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