Changeset 5b46ec8 in mainline

Timestamp:

2017-02-26T22:00:46Z (7 years ago)

Author:

Jakub Jermar <jakub@…>

Branches:

lfn, master, serial, ticket/834-toolchain-update, topic/msim-upgrade, topic/simplify-dev-export

Children:

1dff985, e330da6e

Parents:

b22b449d

Message:

realloc() should try harder to avoid relocating the buffer
(Thanks to Sergio Lopez)

File:

• uspace/lib/c/generic/malloc.c (modified) (1 diff)

uspace/lib/c/generic/malloc.c

@@ -928 +928 @@
                 ptr = ((void *) head) + sizeof(heap_block_head_t);
         } else {
+                heap_block_head_t *next_head =
+                    (heap_block_head_t *) (((void *) head) + head->size);
+                bool have_next = ((void *) next_head < area->end);
+
+                if (((void *) head) + real_size > area->end) {
+                        /*
+                         * The current area is too small to hold the resized
+                         * block. Make sure there are no used blocks standing
+                         * in our way and try to grow the area using real_size
+                         * as a safe upper bound.
+                         */
+
+                        bool have_next_next;
+
+                        if (have_next) {
+                                have_next_next = (((void *) next_head) +
+                                    next_head->size < area->end);
+                        }
+                        if (!have_next || (next_head->free && !have_next_next)) {
+                                /*
+                                 * There is no next block in this area or
+                                 * it is a free block and there is no used
+                                 * block following it. There can't be any
+                                 * free block following it either as
+                                 * two free blocks would be merged.
+                                 */
+                                (void) area_grow(area, real_size);
+                        }
+                }
+                
                 /*
                  * Look at the next block. If it is free and the size is
-                 * sufficient then merge the two. Otherwise just allocate
-                 * a new block, copy the original data into it and
-                 * free the original block.
+                 * sufficient then merge the two. Otherwise just allocate a new
+                 * block, copy the original data into it and free the original
+                 * block.
                  */
-                heap_block_head_t *next_head =
-                    (heap_block_head_t *) (((void *) head) + head->size);
-                
-                if (((void *) next_head < area->end) &&
-                    (head->size + next_head->size >= real_size) &&
-                    (next_head->free)) {
+
+                if (have_next && (head->size + next_head->size >= real_size) &&
+                    next_head->free) {
                         block_check(next_head);
-                        block_init(head, head->size + next_head->size, false, area);
+                        block_init(head, head->size + next_head->size, false,
+                            area);
                         split_mark(head, real_size);
                         
                         ptr = ((void *) head) + sizeof(heap_block_head_t);
                         next_fit = NULL;
-                } else
+                } else {
                         reloc = true;
+                }
         }