[LEDE-DEV] [PATCH] libubox: Fix calloc_a() to return mem aligned pointers

[Ted Hess]

The current implementation of calloc_a() returns packed pointers for the extra
arguments. These packed, unaligned, pointers are OK for a lot of architectures,
but not all. This patch will aligned the pointers returned in a manner congruent
with malloc(). I do not believe the extra padding overhead is all the burdensome
considering the overhead of separate malloc/calloc/free call to accomplish the
same thing.


Signed-off-by: Ted Hess <thess at kitschensync.net>
---
 utils.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/utils.c b/utils.c
index 5d9d5aa..314f716 100644
--- a/utils.c
+++ b/utils.c
@@ -27,6 +27,9 @@
 		_addr; \
 		_addr = va_arg(_arg, void **), _len = _addr ? va_arg(_arg,
size_t) : 0)
 
+#define C_PTR_ALIGN	(2*sizeof(size_t))
+#define C_PTR_MASK	(-C_PTR_ALIGN)
+
 void *__calloc_a(size_t len, ...)
 {
 	va_list ap, ap1;
@@ -40,7 +43,7 @@ void *__calloc_a(size_t len, ...)
 
 	va_copy(ap1, ap);
 	foreach_arg(ap1, cur_addr, cur_len, &ret, len)
-		alloc_len += cur_len;
+		alloc_len += (cur_len + C_PTR_ALIGN - 1 ) & C_PTR_MASK;
 	va_end(ap1);
 
 	ptr = calloc(1, alloc_len);
@@ -49,7 +52,7 @@ void *__calloc_a(size_t len, ...)
 	alloc_len = 0;
 	foreach_arg(ap, cur_addr, cur_len, &ret, len) {
 		*cur_addr = &ptr[alloc_len];
-		alloc_len += cur_len;
+		alloc_len += (cur_len + C_PTR_ALIGN - 1) & C_PTR_MASK;
 	}
 	va_end(ap);
 
-- 
2.7.4