memory.c

#include <stdlib.h>

#include "compiler.h"
#include "memory.h"
#include "vm.h"

#ifdef DEBUG_LOG_GC
#include <stdio.h>
#include "debug.h"
#endif

void* reallocate(void* pointer, size_t oldSize, size_t newSize) {
  if (newSize > oldSize) {
#ifdef DEBUG_STRESS_GC
    collectGarbage();
#endif
  }

  if (newSize == 0) {
    free(pointer);

    return NULL;
  }

  void* result = realloc(pointer, newSize);

  if (result == NULL) exit(1);

  return result;
}

void markObject(Obj* object) {
  if (object == NULL) return;
#ifdef DEBUG_LOG_GC
  printf("%p mark ", (void*)object);
  printValue(OBJ_VAL(object));
  printf("\n");
#endif

  object->isMarked = true;
}

void markValue(Value value) {
  if (IS_OBJ(value)) markObject(AS_OBJ(value));
}

static void freeObject(Obj* object) {
#ifdef DEBUG_LOG_GC
  printf("%p free type %d\n", (void*)object, object->type);
#endif

  switch (object->type) {
    case OBJ_CLOSURE: {
      ObjClosure* closure = (ObjClosure*)object;
      FREE_ARRAY(ObjUpvalue*, closure->upvalues, closure->upvalueCount);
      FREE(ObjClosure, object);
      break;
    }
    case OBJ_FUNCTION: {
      ObjFunction* function = (ObjFunction*)object;
      freeChunk(&function->chunk);
      FREE(ObjFunction, object);
      break;
    }
    case OBJ_NATIVE: {
      FREE(ObjNative, object);
      break;
    }
    case OBJ_STRING: {
      ObjString* string = (ObjString*)object;
      FREE_ARRAY(char, string->chars, string->length + 1);
      // going through reallocate instead of calling free() will make it easier
      // to keep track of how much memory is in use.
      FREE(ObjString, object);
      break;
    }
    case OBJ_UPVALUE: {
      FREE(ObjUpvalue, object);
      break;
    }
  }
}

static void markRoots() {
  for (Value* slot = vm.stack; slot < vm.stackTop; slot++) {
    markValue(*slot);
  }

  for (int i = 0; i < vm.frameCount; i++) {
    markObject((Obj*)vm.frames[i].closure);
  }

  for (ObjUpvalue* upvalue = vm.openUpvalues; upvalue != NULL; upvalue = upvalue->next) {
    markObject((Obj*)upvalue);
  }

  markTable(&vm.globals);
  markCompilerRoots();
}

void collectGarbage() {
#ifdef DEBUG_LOG_GC
  printf("--gc begin\n");
#endif

  markRoots();

#ifdef DEBUG_LOG_GC
  printf("--gc end\n");
#endif
}

void freeObjects() {
  Obj* object = vm.objects;
  while (object != NULL) {
    Obj* next = object->next;
    freeObject(object);
    object = next;
  }
}