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authorRich Felker <dalias@aerifal.cx>2018-04-19 20:45:48 -0400
committerRich Felker <dalias@aerifal.cx>2018-04-19 20:45:48 -0400
commit3c2cbbe7ba8b4486299ae0d5336ae01ab520d116 (patch)
treef269c212fa64c10f68e990550ef6c91c885592e3
parent23389b1988b061e8487c316893a8a8eb77770a2f (diff)
downloadmusl-3c2cbbe7ba8b4486299ae0d5336ae01ab520d116.tar.gz
using malloc implementation types/macros/idioms for memalign
the generated code should be mostly unchanged, except for explicit use of C_INUSE in place of copying the low bits from existing chunk headers/footers. these changes also remove mild UB due to dubious arithmetic on pointers into imaginary size_t[] arrays.
-rw-r--r--src/malloc/memalign.c42
1 files changed, 22 insertions, 20 deletions
diff --git a/src/malloc/memalign.c b/src/malloc/memalign.c
index 8fb2002c..9c420229 100644
--- a/src/malloc/memalign.c
+++ b/src/malloc/memalign.c
@@ -2,49 +2,51 @@
#include <stdint.h>
#include <errno.h>
#include "libc.h"
+#include "malloc_impl.h"
void *__memalign(size_t align, size_t len)
{
- unsigned char *mem, *new, *end;
- size_t header, footer;
+ unsigned char *mem, *new;
if ((align & -align) != align) {
errno = EINVAL;
- return NULL;
+ return 0;
}
if (len > SIZE_MAX - align) {
errno = ENOMEM;
- return NULL;
+ return 0;
}
- if (align <= 4*sizeof(size_t)) {
- if (!(mem = malloc(len)))
- return NULL;
- return mem;
- }
+ if (align <= SIZE_ALIGN)
+ return malloc(len);
if (!(mem = malloc(len + align-1)))
- return NULL;
+ return 0;
new = (void *)((uintptr_t)mem + align-1 & -align);
if (new == mem) return mem;
- header = ((size_t *)mem)[-1];
+ struct chunk *c = MEM_TO_CHUNK(mem);
+ struct chunk *n = MEM_TO_CHUNK(new);
- if (!(header & 7)) {
- ((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem);
- ((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem);
+ if (IS_MMAPPED(c)) {
+ /* Apply difference between aligned and original
+ * address to the "extra" field of mmapped chunk. */
+ n->psize = c->psize + (new-mem);
+ n->csize = c->csize - (new-mem);
return new;
}
- end = mem + (header & -8);
- footer = ((size_t *)end)[-2];
+ struct chunk *t = NEXT_CHUNK(c);
- ((size_t *)mem)[-1] = header&7 | new-mem;
- ((size_t *)new)[-2] = footer&7 | new-mem;
- ((size_t *)new)[-1] = header&7 | end-new;
- ((size_t *)end)[-2] = footer&7 | end-new;
+ /* Split the allocated chunk into two chunks. The aligned part
+ * that will be used has the size in its footer reduced by the
+ * difference between the aligned and original addresses, and
+ * the resulting size copied to its header. A new header and
+ * footer are written for the split-off part to be freed. */
+ n->psize = c->csize = C_INUSE | (new-mem);
+ n->csize = t->psize -= new-mem;
free(mem);
return new;