summaryrefslogtreecommitdiff
path: root/libc/stdlib/malloc
diff options
context:
space:
mode:
Diffstat (limited to 'libc/stdlib/malloc')
-rw-r--r--libc/stdlib/malloc/heap.h2
-rw-r--r--libc/stdlib/malloc/malloc.h18
2 files changed, 14 insertions, 6 deletions
diff --git a/libc/stdlib/malloc/heap.h b/libc/stdlib/malloc/heap.h
index 23358d988..ecc432b8e 100644
--- a/libc/stdlib/malloc/heap.h
+++ b/libc/stdlib/malloc/heap.h
@@ -25,7 +25,7 @@
/* The heap allocates in multiples of, and aligned to, HEAP_GRANULARITY.
HEAP_GRANULARITY must be a power of 2. Malloc depends on this being the
same as MALLOC_ALIGNMENT. */
-#define HEAP_GRANULARITY_TYPE double
+#define HEAP_GRANULARITY_TYPE double __attribute_aligned__ (sizeof (size_t))
#define HEAP_GRANULARITY (__alignof__ (HEAP_GRANULARITY_TYPE))
diff --git a/libc/stdlib/malloc/malloc.h b/libc/stdlib/malloc/malloc.h
index 747e8bf9e..78232d62d 100644
--- a/libc/stdlib/malloc/malloc.h
+++ b/libc/stdlib/malloc/malloc.h
@@ -11,8 +11,13 @@
* Written by Miles Bader <miles@gnu.org>
*/
-/* The alignment we guarantee for malloc return values. */
-#define MALLOC_ALIGNMENT (__alignof__ (double))
+/* The alignment we guarantee for malloc return values. We prefer this
+ to be at least sizeof (size_t) bytes because (a) we have to allocate
+ that many bytes for the header anyway and (b) guaranteeing word
+ alignment can be a significant win on targets like m68k and Coldfire,
+ where __alignof__(double) == 2. */
+#define MALLOC_ALIGNMENT \
+ __alignof__ (double __attribute_aligned__ (sizeof (size_t)))
/* The system pagesize... */
extern size_t __pagesize;
@@ -98,17 +103,20 @@ extern int __malloc_mmb_debug;
/* The size of a malloc allocation is stored in a size_t word
- MALLOC_ALIGNMENT bytes prior to the start address of the allocation:
+ MALLOC_HEADER_SIZE bytes prior to the start address of the allocation:
+--------+---------+-------------------+
| SIZE |(unused) | allocation ... |
+--------+---------+-------------------+
^ BASE ^ ADDR
- ^ ADDR - MALLOC_ALIGN
+ ^ ADDR - MALLOC_HEADER_SIZE
*/
/* The amount of extra space used by the malloc header. */
-#define MALLOC_HEADER_SIZE MALLOC_ALIGNMENT
+#define MALLOC_HEADER_SIZE \
+ (MALLOC_ALIGNMENT < sizeof (size_t) \
+ ? sizeof (size_t) \
+ : MALLOC_ALIGNMENT)
/* Set up the malloc header, and return the user address of a malloc block. */
#define MALLOC_SETUP(base, size) \