Implement shrinking.

Fix bug when growing an allocation.
Use new malloc header macros.

diff --git a/libc/stdlib/malloc/realloc.c b/libc/stdlib/malloc/realloc.c
index 7a89712..34118ab 100644 (file)
--- a/libc/stdlib/malloc/realloc.c
+++ b/libc/stdlib/malloc/realloc.c
@@ -25,19 +25,22 @@ realloc (void *mem, size_t new_size)
     return malloc (new_size);
   else
     {
-      void *base_mem = mem - MALLOC_ALIGNMENT;
-      size_t size = *(size_t *)base_mem;
+      char *base_mem = MALLOC_BASE (mem);
+      size_t size = MALLOC_SIZE (mem);
+
+      /* Make sure that we're dealing in a multiple of the heap allocation
+        unit (SIZE is already guaranteed to be so).  */
+      // new_size = HEAP_ADJUST_SIZE (new_size);
 
       MALLOC_DEBUG ("realloc: 0x%lx, %d (base = 0x%lx, total_size = %d)\n",
                    (long)mem, new_size, (long)base_mem, size);
 
-      if (new_size <= size)
-       return mem;
-      else
+      if (new_size > size)
+       /* Grow the block.  */
        {
          void *new_mem = 0;
          size_t ext_size = new_size - size;
-         void *ext_addr = (char *)base_mem + ext_size;
+         void *ext_addr = base_mem + size;
 
          __malloc_lock ();
          ext_size = __heap_alloc_at (&__malloc_heap, ext_addr, ext_size);
@@ -62,5 +65,15 @@ realloc (void *mem, size_t new_size)
 
          return new_mem;
        }
+      else if (new_size + HEAP_MIN_FREE_AREA_SIZE <= size)
+       /* Shrink the block.  */
+       {
+         __malloc_lock ();
+         __heap_free (&__malloc_heap, base_mem + new_size, new_size - size);
+         __malloc_unlock ();
+       }
+      else
+       /* Do nothing.  */
+       return mem;
     }
 }