diff options
| -rw-r--r-- | include/sys/cdefs.h | 8 | ||||
| -rw-r--r-- | libc/stdlib/malloc/heap.h | 2 | ||||
| -rw-r--r-- | libc/stdlib/malloc/malloc.h | 18 |
3 files changed, 22 insertions, 6 deletions
diff --git a/include/sys/cdefs.h b/include/sys/cdefs.h index fb53924e9..8daac15ef 100644 --- a/include/sys/cdefs.h +++ b/include/sys/cdefs.h @@ -189,6 +189,14 @@ # define __attribute__(xyz) /* Ignore */ #endif +/* We make this a no-op unless it can be used as both a variable and + a type attribute. gcc 2.8 is known to support both. */ +#if __GNUC_PREREQ (2,8) +# define __attribute_aligned__(size) __attribute__ ((__aligned__ (size))) +#else +# define __attribute_aligned__(size) /* Ignore */ +#endif + /* At some point during the gcc 2.96 development the `malloc' attribute for functions was introduced. We don't want to use it unconditionally (although this would be possible) since it generates warnings. */ 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) \ |