From ce478b0b80af331b89813148df7b04d46968e328 Mon Sep 17 00:00:00 2001
From: Tom Willemse <tom@ryuslash.org>
Date: Sun, 23 Jan 2022 15:58:35 -0800
Subject: [PATCH] Chapter 24.3

---
 clox/src/vm.c | 54 ++++++++++++++++++++++++++++-----------------------
 clox/src/vm.h | 13 +++++++++++--
 2 files changed, 41 insertions(+), 26 deletions(-)

diff --git a/clox/src/vm.c b/clox/src/vm.c
index c1c6941..7dd79a3 100644
--- a/clox/src/vm.c
+++ b/clox/src/vm.c
@@ -11,7 +11,10 @@
 
 VM vm;
 
-static void resetStack() { vm.stackTop = vm.stack; }
+static void resetStack() {
+  vm.stackTop = vm.stack;
+  vm.frameCount = 0;
+}
 
 static void runtimeError(const char *format, ...) {
   va_list args;
@@ -20,8 +23,9 @@ static void runtimeError(const char *format, ...) {
   va_end(args);
   fputs("\n", stderr);
 
-  size_t instruction = vm.ip - vm.chunk->code - 1;
-  int line = vm.chunk->lines[instruction];
+  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);
   resetStack();
 }
@@ -71,9 +75,14 @@ static void concatenate() {
 }
 
 static InterpretResult run() {
-#define READ_BYTE() (*vm.ip++)
-#define READ_CONSTANT() (vm.chunk->constants.values[READ_BYTE()])
-#define READ_SHORT() (vm.ip += 2, (uint16_t)((vm.ip[-2] << 8) | vm.ip[-1]))
+  CallFrame *frame = &vm.frames[vm.frameCount - 1];
+
+#define READ_BYTE() (*frame->ip++)
+
+#define READ_SHORT()                                                           \
+  (frame->ip += 2, (uint16_t)((frame->ip[-2] << 8) | frame->ip[-1]))
+
+#define READ_CONSTANT() (frame->function->chunk.constants.values[READ_BYTE()])
 #define READ_STRING() AS_STRING(READ_CONSTANT())
 #define BINARY_OP(valueType, op)                                               \
   do {                                                                         \
@@ -94,7 +103,8 @@ static InterpretResult run() {
       printf(" ]");
     }
     printf("\n");
-    disassembleInstruction(vm.chunk, (int)(vm.ip - vm.chunk->code));
+    disassembleInstruction(&frame->function->chunk,
+                           (int)(frame->ip - frame->function->chunk.code));
 #endif
 
     uint8_t instruction;
@@ -118,12 +128,12 @@ static InterpretResult run() {
       break;
     case OP_GET_LOCAL: {
       uint8_t slot = READ_BYTE();
-      push(vm.stack[slot]);
+      push(frame->slots[slot]);
       break;
     }
     case OP_SET_LOCAL: {
       uint8_t slot = READ_BYTE();
-      vm.stack[slot] = peek(0);
+      frame->slots[slot] = peek(0);
       break;
     }
     case OP_GET_GLOBAL: {
@@ -202,18 +212,18 @@ static InterpretResult run() {
     }
     case OP_JUMP: {
       uint16_t offset = READ_SHORT();
-      vm.ip += offset;
+      frame->ip += offset;
       break;
     }
     case OP_JUMP_IF_FALSE: {
       uint16_t offset = READ_SHORT();
       if (isFalsey(peek(0)))
-        vm.ip += offset;
+        frame->ip += offset;
       break;
     }
     case OP_LOOP: {
       uint16_t offset = READ_SHORT();
-      vm.ip -= offset;
+      frame->ip -= offset;
       break;
     }
     case OP_RETURN: {
@@ -235,19 +245,15 @@ static InterpretResult run() {
 }
 
 InterpretResult interpret(const char *source) {
-  Chunk chunk;
-  initChunk(&chunk);
-
-  if (!compile(source, &chunk)) {
-    freeChunk(&chunk);
+  ObjFunction *function = compile(source);
+  if (function != NULL)
     return INTERPRET_COMPILE_ERROR;
-  }
 
-  vm.chunk = &chunk;
-  vm.ip = vm.chunk->code;
+  push(OBJ_VAL(function));
+  CallFrame *frame = &vm.frames[vm.frameCount++];
+  frame->function = function;
+  frame->ip = function->chunk.code;
+  frame->slots = vm.stack;
 
-  InterpretResult result = run();
-
-  freeChunk(&chunk);
-  return result;
+  return run();
 }
diff --git a/clox/src/vm.h b/clox/src/vm.h
index 0ab269b..170166b 100644
--- a/clox/src/vm.h
+++ b/clox/src/vm.h
@@ -2,14 +2,23 @@
 #define clox_vm_h
 
 #include "chunk.h"
+#include "object.h"
 #include "table.h"
 #include "value.h"
 
-#define STACK_MAX 256
+#define FRAMES_MAX 64
+#define STACK_MAX (FRAMES_MAX * UINT8_COUNT)
 
 typedef struct {
-  Chunk *chunk;
+  ObjFunction *function;
   uint8_t *ip;
+  Value *slots;
+} CallFrame;
+
+typedef struct {
+  CallFrame frames[FRAMES_MAX];
+  int frameCount;
+
   Value stack[STACK_MAX];
   Value *stackTop;
   Table globals;