move core memalign code from aligned_alloc to __memalign

there are two motivations for this change. one is to avoid
gratuitously depending on a C11 symbol for implementing a POSIX
function. the other pertains to the documented semantics. C11 does not
define any behavior for aligned_alloc when the length argument is not
a multiple of the alignment argument. posix_memalign on the other hand
places no requirements on the length argument. using __memalign as the
implementation of both, rather than trying to implement one in terms
of the other when their documented contracts differ, eliminates this
confusion.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/malloc/posix_memalign.c b/src/malloc/posix_memalign.c
index ad4d8f47..cf67db63 100644
--- a/src/malloc/posix_memalign.c
+++ b/src/malloc/posix_memalign.c
@@ -1,10 +1,12 @@
 #include <stdlib.h>
 #include <errno.h>
 
+void *__memalign(size_t, size_t);
+
 int posix_memalign(void **res, size_t align, size_t len)
 {
 	if (align < sizeof(void *)) return EINVAL;
-	void *mem = aligned_alloc(align, len);
+	void *mem = __memalign(align, len);
 	if (!mem) return errno;
 	*res = mem;
 	return 0;