From 6d861ac87491a207e4599c44b61d142f0a601c2d Mon Sep 17 00:00:00 2001 From: Rich Felker Date: Thu, 4 Jul 2013 23:58:16 -0400 Subject: 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. --- src/malloc/memalign.c | 52 +++++++++++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 50 insertions(+), 2 deletions(-) (limited to 'src/malloc/memalign.c') diff --git a/src/malloc/memalign.c b/src/malloc/memalign.c index a594c636..55fe68e8 100644 --- a/src/malloc/memalign.c +++ b/src/malloc/memalign.c @@ -1,7 +1,55 @@ #include +#include #include +#include "libc.h" -void *memalign(size_t align, size_t len) +/* This function should work with most dlmalloc-like chunk bookkeeping + * systems, but it's only guaranteed to work with the native implementation + * used in this library. */ + +void *__memalign(size_t align, size_t len) { - return aligned_alloc(align, len); + unsigned char *mem, *new, *end; + size_t header, footer; + + if ((align & -align) != align) { + errno = EINVAL; + return NULL; + } + + if (len > SIZE_MAX - align) { + errno = ENOMEM; + return NULL; + } + + if (align <= 4*sizeof(size_t)) { + if (!(mem = malloc(len))) + return NULL; + return mem; + } + + if (!(mem = malloc(len + align-1))) + return NULL; + + header = ((size_t *)mem)[-1]; + new = (void *)((uintptr_t)mem + align-1 & -align); + + if (!(header & 7)) { + ((size_t *)new)[-2] = ((size_t *)mem)[-2] + (new-mem); + ((size_t *)new)[-1] = ((size_t *)mem)[-1] - (new-mem); + return new; + } + + end = mem + (header & -8); + footer = ((size_t *)end)[-2]; + + ((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; + + if (new != mem) free(mem); + return new; } + +weak_alias(__memalign, memalign); -- cgit v1.2.1