Bugfix

Makefile

@@ -2,8 +2,8 @@
 # Students' Makefile for the Malloc Lab
 #
 CC = gcc
-# CFLAGS = -Wall -O2 -m32 -g03 -pg
-CFLAGS = -Wall -O0 -m32 -g03 -pg
+CFLAGS = -Wall -O2 -m32
+# CFLAGS = -Wall -O0 -m32 -g03 -pg
 
 OBJS = mdriver.o mm.o memlib.o fsecs.o fcyc.o clock.o ftimer.o
 

mm.c

@@ -102,7 +102,7 @@ team_t team = {
 #define NEXT_BLKP(bp) ((char *)(bp) + GET_SIZE(((char *)(bp) - WSIZE)))
 #define PREV_BLKP(bp) ((char *)(bp) - GET_SIZE(((char *)(bp) - DSIZE)))
 
-#define PUT_PTR(p, ptr) (*(unsigned int *)(p) = (unsigned int)(ptr))
+#define PUT_PTR(p, ptr) (*(unsigned int *)(p) = (size_t)(ptr))
 
 #define PRV_PTR(ptr) ((char *)(ptr))
 #define NXT_PTR(ptr) ((char *)(ptr) + WSIZE)
@@ -117,202 +117,198 @@ team_t team = {
 static char* heap_listp;
 char* seg_list[LISTSIZE];
 
-static void insert_node(void *ptr, size_t size) {
-  int list = 0;
-  void *search_ptr = ptr;
-  void *insert_ptr = NULL;
+////////////////////////////////////////////////////////////////////////////////
+///////////////////////////////// HELPER PREDEF //////////////////////////////// 
+////////////////////////////////////////////////////////////////////////////////
+/**
+   @brief Extends the memory of the heap by the specified amount.
+
+   @param[in] size amount of memory to extend heap by
+   @result Pointer to the newly allocated memory area.
+ */
+static void *extend_heap(size_t size);
+
+/**
+   @brief Adds a free memory location to the segregated list.
+   
+   @param[in] ptr Pointer of the memory location to be added
+   @param[in] size size of the area that would be occupied
+*/
+static void add_free(void *ptr, size_t size);
+
+/**
+   @brief Removes a free memory location to the segregated list.
+   
+   @param[in] ptr Pointer of the memory location to be removed
+*/
+static void remove_free(void *ptr);
+
+/**
+   @brief Coalesce memory areas around the given pointer, given that they're free.
+   
+   @param[in] ptr Memory area to look into.
+*/
+static void *coalesce(void *ptr);
+
+/**
+   @brief Places The header and footer for our memory blocks.
+   
+   @param[in] ptr pointer to the memory block that's allocated
+   @param[in] asize size of memory to allocate
+*/
+static void *place(void *ptr, size_t asize);
+
+/**
+   @brief Get the size class of the given size inside of the segregated list
+   
+   @param[in] asize size class to look for in segregated list
+   @result Size class (i.e. index of segregated list)
+*/
+static inline int getSzClass(size_t asize);
+
+////////////////////////////////////////////////////////////////////////////////
+/////////////////////////////// HELPER FUNCTIONS /////////////////////////////// 
+////////////////////////////////////////////////////////////////////////////////
+static inline int getSzClass(size_t asize) {
+  int i;
+  for (i = 0; i < LISTSIZE-1; ++i) {
+    if (asize <= 1)
+      break;
+    asize >>= 1;
+  }
+  return i;
+}
+
+static void *extend_heap(size_t size)
+{
+  size_t asize;
+  asize = ALIGN(size);
+  void *ptr;                   
     
-  // Select segregated list 
-  while ((list < LISTSIZE - 1) && (size > 1)) {
-    size >>= 1;
-    list++;
+  if ((ptr = mem_sbrk(asize)) == (void *)-1)
+    return NULL;
+    
+  /* Set Header and Footer*/
+  PUT(HDRP(ptr), PACK(asize, 0));  
+  PUT(FTRP(ptr), PACK(asize, 0));   
+  PUT(HDRP(NEXT_BLKP(ptr)), PACK(0, 1)); 
+
+  add_free(ptr, asize);
+
+  return coalesce(ptr);
+}
+
+static void add_free(void *ptr, size_t size) {
+  int szClass = getSzClass(size);
+  void* class_ptr = seg_list[szClass];
+  void *pre_ptr = NULL;
+
+  while ((class_ptr != NULL) && (size > GET_SIZE(HDRP(class_ptr)))) {
+    pre_ptr = class_ptr;
+    class_ptr = PRV_BLK(class_ptr);
   }
     
-  // Keep size ascending order and search
-  search_ptr = seg_list[list];
-  while ((search_ptr != NULL) && (size > GET_SIZE(HDRP(search_ptr)))) {
-    insert_ptr = search_ptr;
-    search_ptr = PRV_BLK(search_ptr);
-  }
-    
-  // Set predecessor and successor 
-  if (search_ptr != NULL) {
-    if (insert_ptr != NULL) {
-      PUT_PTR(PRV_PTR(ptr), search_ptr);
-      PUT_PTR(NXT_PTR(search_ptr), ptr);
-      PUT_PTR(NXT_PTR(ptr), insert_ptr);
-      PUT_PTR(PRV_PTR(insert_ptr), ptr);
-    } else {
-      PUT_PTR(PRV_PTR(ptr), search_ptr);
-      PUT_PTR(NXT_PTR(search_ptr), ptr);
-      PUT_PTR(NXT_PTR(ptr), NULL);
-      seg_list[list] = ptr;
-    }
-  } else {
-    if (insert_ptr != NULL) {
-      PUT_PTR(PRV_PTR(ptr), NULL);
-      PUT_PTR(NXT_PTR(ptr), insert_ptr);
-      PUT_PTR(PRV_PTR(insert_ptr), ptr);
-    } else {
-      PUT_PTR(PRV_PTR(ptr), NULL);
-      PUT_PTR(NXT_PTR(ptr), NULL);
-      seg_list[list] = ptr;
-    }
+  if (class_ptr != NULL && pre_ptr != NULL) {
+    PUT_PTR(NXT_PTR(class_ptr), ptr);
+    PUT_PTR(NXT_PTR(ptr), pre_ptr);
+    PUT_PTR(PRV_PTR(ptr), class_ptr);
+    PUT_PTR(PRV_PTR(pre_ptr), ptr);
+  } 
+  else if (class_ptr != NULL && pre_ptr == NULL) {
+    PUT_PTR(PRV_PTR(ptr), class_ptr);
+    PUT_PTR(NXT_PTR(class_ptr), ptr);
+    PUT_PTR(NXT_PTR(ptr), NULL);
+    seg_list[szClass] = ptr;
+  } 
+  else if(class_ptr == NULL && pre_ptr != NULL) {
+    PUT_PTR(NXT_PTR(ptr), pre_ptr);
+    PUT_PTR(PRV_PTR(ptr), NULL);
+    PUT_PTR(PRV_PTR(pre_ptr), ptr);
+  } 
+  else {
+    PUT_PTR(NXT_PTR(ptr), NULL);
+    PUT_PTR(PRV_PTR(ptr), NULL);
+    seg_list[szClass] = ptr;
   }
     
   return;
 }
-////////////////////////////////////////////////////////////////////////////////
-///////////////////////////////// HELPER PREDEF //////////////////////////////// 
-////////////////////////////////////////////////////////////////////////////////
-/* Page 856-858, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void place(void *bp, size_t asize);
-/* Page 856, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void* find_fit(size_t asize);
-/* Page 833, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void* coalesce(void *bp);
-/* Page 831, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void* extend_heap(size_t words);
-static void add_free(void* bp, size_t asize);
-////////////////////////////////////////////////////////////////////////////////
-/////////////////////////////// HELPER FUNCTIONS /////////////////////////////// 
-////////////////////////////////////////////////////////////////////////////////
-static void add_free(void* bp, size_t asize) {
-  insert_node(bp, asize);
-}
-static int getSzClass(size_t asize) {
-  for (size_t i = 0; i < LISTSIZE; ++i) {
-    if (asize == (1 << i)) {
-      return i;
-    }
-  }
-  return LISTSIZE-1;
-}
 
-static void remove_free(void* bp) {
-  int szClass = getSzClass(GET_SIZE(HDRP(bp)));
 
-  if (PRV_BLK(bp) == NULL && NXT_BLK(bp) == NULL) {
+static void remove_free(void *ptr) {
+  size_t size = GET_SIZE(HDRP(ptr));
+  int szClass = getSzClass(size);
+    
+  if (PRV_BLK(ptr) != NULL && NXT_BLK(ptr) != NULL) {
+    PUT_PTR(NXT_PTR(PRV_BLK(ptr)), NXT_BLK(ptr));
+    PUT_PTR(PRV_PTR(NXT_BLK(ptr)), PRV_BLK(ptr));
+  } else if(PRV_BLK(ptr) != NULL && NXT_BLK(ptr) == NULL) {
+    PUT_PTR(NXT_PTR(PRV_BLK(ptr)), NULL);
+    seg_list[szClass] = PRV_BLK(ptr);
+  } 
+  else if(PRV_BLK(ptr) == NULL && NXT_BLK(ptr) != NULL) {
+    PUT_PTR(PRV_PTR(NXT_BLK(ptr)), NULL);
+  } else {
     seg_list[szClass] = NULL;
-  } else if (PRV_BLK(bp) != NULL && NXT_BLK(bp) == NULL) {
-    PUT_PTR(PRV_PTR(PRV_BLK(bp)), NULL);
-    seg_list[szClass] = PRV_BLK(bp);
-  } else if (PRV_BLK(bp) == NULL && NXT_BLK(bp) != NULL) {
-    PUT_PTR(PRV_PTR(NXT_BLK(bp)), NULL);
-  } if (PRV_BLK(bp) != NULL && NXT_BLK(bp) != NULL) { 
-    PUT_PTR(NXT_PTR(PRV_BLK(bp)), NXT_BLK(bp));
-    PUT_PTR(PRV_PTR(NXT_BLK(bp)), PRV_BLK(bp));
-  }
+  }  
+  return;
 }
 
-static void place(void *bp, size_t asize)
-{
-  size_t csize = GET_SIZE(HDRP(bp));
 
-  remove_free(bp);
+static void *coalesce(void *ptr) {
+  size_t prev_alloc = GET_ALLOC(HDRP(PREV_BLKP(ptr)));
+  size_t next_alloc = GET_ALLOC(HDRP(NEXT_BLKP(ptr)));
+  size_t size = GET_SIZE(HDRP(ptr));
+    
+  if (prev_alloc && next_alloc) {                         // Case 1
+    return ptr;
+  }
+  else if (prev_alloc && !next_alloc) {                   // Case 2
+    remove_free(ptr);
+    remove_free(NEXT_BLKP(ptr));
+    size += GET_SIZE(HDRP(NEXT_BLKP(ptr)));
+    PUT(HDRP(ptr), PACK(size, 0));
+    PUT(FTRP(ptr), PACK(size, 0));
+  } else if (!prev_alloc && next_alloc) {                 // Case 3 
+    remove_free(ptr);
+    remove_free(PREV_BLKP(ptr));
+    size += GET_SIZE(HDRP(PREV_BLKP(ptr)));
+    PUT(FTRP(ptr), PACK(size, 0));
+    PUT(HDRP(PREV_BLKP(ptr)), PACK(size, 0));
+    ptr = PREV_BLKP(ptr);
+  } else {                                                // Case 4
+    remove_free(ptr);
+    remove_free(PREV_BLKP(ptr));
+    remove_free(NEXT_BLKP(ptr));
+    size += GET_SIZE(HDRP(PREV_BLKP(ptr))) + GET_SIZE(HDRP(NEXT_BLKP(ptr)));
+    PUT(HDRP(PREV_BLKP(ptr)), PACK(size, 0));
+    PUT(FTRP(NEXT_BLKP(ptr)), PACK(size, 0));
+    ptr = PREV_BLKP(ptr);
+  }
+    
+  add_free(ptr, size);
+    
+  return ptr;
+}
 
-  PUT(HDRP(bp), PACK(csize, 1));
-  PUT(FTRP(bp), PACK(csize, 1));
-  if (asize <= (2*(1 << (LISTSIZE-1)))) {
-    return;
+static void *place(void *ptr, size_t asize) {
+  size_t ptr_size = GET_SIZE(HDRP(ptr));
+  size_t rest = ptr_size - asize;
+    
+  remove_free(ptr);
+    
+  if (rest <= DSIZE * 2) {
+    PUT(HDRP(ptr), PACK(ptr_size, 1)); 
+    PUT(FTRP(ptr), PACK(ptr_size, 1)); 
   } else {
-    bp = NEXT_BLKP(bp);
-    PUT(HDRP(bp), PACK(csize-asize, 0));
-    PUT(FTRP(bp), PACK(csize-asize, 0));
-    add_free(bp, csize-asize);
+    PUT(HDRP(ptr), PACK(rest, 0));
+    PUT(FTRP(ptr), PACK(rest, 0));
+    PUT(HDRP(NEXT_BLKP(ptr)), PACK(asize, 1));
+    PUT(FTRP(NEXT_BLKP(ptr)), PACK(asize, 1));
+    add_free(ptr, rest);
+    return NEXT_BLKP(ptr);
   }
-}
-
-static void* best_fit(void* ptr, size_t asize) {
-  unsigned long left_over = GET_SIZE(ptr) - asize;
-  void* bestfit = ptr;
-  unsigned long best_left_over = GET_SIZE(ptr) - asize;
-  while (NXT_PTR(ptr) != NULL) {
-    left_over = GET_SIZE(ptr) - asize;
-    if(left_over<best_left_over){
-      best_left_over = left_over;
-      bestfit=ptr;
-    }  
-    ptr = NXT_BLK(ptr);
-  }
-  return bestfit;
-}
-/* Page 856, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void* find_fit(size_t asize)
-{
-  int szClass  = getSzClass(asize);
-  void* classPtr = seg_list[szClass];
-  if (classPtr == NULL) {
-    return NULL;
-  } else {
-    if (szClass != LISTSIZE -1) {
-    while (NXT_PTR(classPtr) != NULL) {
-      classPtr = NXT_BLK(classPtr);
-    }
-    return classPtr;
-    } else {
-      return best_fit(classPtr, asize);
-    }
-  }
-}
-
-/* Page 833, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void *coalesce(void *bp) {
-  size_t prev_alloc = GET_ALLOC(FTRP(PREV_BLKP(bp)));
-  size_t next_alloc = GET_ALLOC(HDRP(NEXT_BLKP(bp)));
-  size_t size = GET_SIZE(HDRP(bp));
-
-  if (prev_alloc && next_alloc) {                /* Case 1 */
-    return bp;
-  } else if (prev_alloc && !next_alloc) {        /* Case 2 */
-    remove_free(bp);
-    remove_free(NEXT_BLKP(bp));
-    size += GET_SIZE(HDRP(NEXT_BLKP(bp)));
-    PUT(HDRP(bp),PACK(size,0));
-    PUT(FTRP(bp),PACK(size,0));
-  } else if (!prev_alloc && next_alloc) {        /* Case 3 */
-    remove_free(bp);
-    remove_free(PREV_BLKP(bp));
-    size += GET_SIZE(HDRP(PREV_BLKP(bp)));
-    PUT(FTRP(bp), PACK(size, 0));
-    PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
-    bp = PREV_BLKP(bp);
-  } else {                                       /* Case 4 */
-    remove_free(bp);
-    remove_free(PREV_BLKP(bp));
-    remove_free(NEXT_BLKP(bp));
-    size += GET_SIZE(HDRP(PREV_BLKP(bp))) +
-      GET_SIZE(FTRP(NEXT_BLKP(bp)));
-    PUT(HDRP(PREV_BLKP(bp)), PACK(size, 0));
-    PUT(FTRP(NEXT_BLKP(bp)), PACK(size, 0));
-    bp = PREV_BLKP(bp);
-  }
-
-  add_free(bp, size);
-  
-  return bp;
-}
-
-/* Page 831, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
-static void *extend_heap(size_t words)
-{
-  char *bp;
-  size_t size;
-
-  /* Allocate an even number of words to maintain alignment */
-  size = (words % 2) ? (words+1) * WSIZE : words * WSIZE;
-  if ((long)(bp = mem_sbrk(size)) == -1)
-    return NULL;
-
-  /* Initialize free block header/footer and the epilogue header */
-  PUT(HDRP(bp), PACK(size,0)); /* Free block header */
-  PUT(FTRP(bp), PACK(size,0)); /* Free block footer */
-  PUT(HDRP(NEXT_BLKP(bp)), PACK(0, 1)); /* New epilogue header */
-
-  add_free(bp, size);
-
-  /* Coalesce if the previous block was free */
-  return coalesce(bp);
+  return ptr;
 }
 
 ////////////////////////////////////////////////////////////////////////////////
@@ -324,7 +320,7 @@ static void *extend_heap(size_t words)
  */
 int mm_init(void)
 {
-  // init seg_list
+  // Init seg_list
   for (size_t i = 0; i < LISTSIZE; ++i) {
     seg_list[i] = NULL;
   }
@@ -351,32 +347,41 @@ int mm_init(void)
  */
 void *mm_malloc(size_t size)
 {
-  size_t asize; /* Adjusted block size */
+  size_t asize;      /* Adjusted block size */
   size_t extendsize; /* Amount to extend heap if no fit */
-  char *bp; /* Pointer */
-
-  /* Ignore spurious requests */
+  void *ptr;  /* Pointer */
+    
   if (size == 0)
     return NULL;
-
-  /* Adjust block size to include overhead and alignment reqs. */
-  if (size <= DSIZE)
-    asize = 2*DSIZE;
-  else
+    
+  if (size <= DSIZE) {
+    asize = 2 * DSIZE;
+  } else {
     asize = ALIGN(size+DSIZE);
-
-  /* Search the free list for a fit */
-  if ((bp = find_fit(asize)) != NULL) {
-    place(bp, asize);
-    return bp;
   }
-
-  /* No fit found. Get more memory and place the block */
-  extendsize = MAX(asize,CHUNKSIZE);
-  if ((bp = extend_heap(extendsize/WSIZE)) == NULL)
-    return NULL;
-  place(bp, asize);
-  return bp;
+    
+  size_t sz = asize;
+  for (int i = 0;i < LISTSIZE; ++i) {
+    if ((i == LISTSIZE-1) || ((sz < 2) && (seg_list[i] != NULL))) {
+      ptr = seg_list[i];
+      while (!((ptr == NULL) || (asize <= GET_SIZE(HDRP(ptr)))))
+        {
+          ptr = PRV_BLK(ptr);
+        }
+      if (ptr != NULL)
+        break;
+    }
+    sz >>= 1;
+  }
+    
+  if (ptr == NULL) {
+    extendsize = MAX(asize, CHUNKSIZE);
+        
+    if ((ptr = extend_heap(extendsize)) == NULL)
+      return NULL;
+  }
+    
+  return place(ptr, asize);
 }
 
 /* Page 833, Pearson R. Bryant – D. O’Hallaron. Computer Systems: A Programmer’s Perspective.3rd Edition, Pearson, 2003. */
@@ -386,6 +391,7 @@ void *mm_malloc(size_t size)
 void mm_free(void *ptr)
 {
   size_t size = GET_SIZE(HDRP(ptr));
+  add_free(ptr, size);
   PUT(HDRP(ptr), PACK(size, 0));
   PUT(FTRP(ptr), PACK(size, 0));