sdsheader: cast pointer through void pointer

Because a char* and struct sdshdr pointer have a different alignment you
get the following warning when try to cast it directly:

    warning: cast from 'sds' (aka 'char *') to 'struct sdshdr *' increases
        required alignment from 1 to 8 [-Wcast-align]

To silence the warning we cast it to a void pointer first.

1 files changed, 3 insertions, 1 deletions

diff --git a/src/sds.h b/src/sds.h
index a46b06b..d0830fe 100644
--- a/src/sds.h
+++ b/src/sds.h
@@ -43,7 +43,9 @@ struct sdshdr {
 };
 
 static inline struct sdshdr * sdsheader(const sds s) {
-	return s - (sizeof (struct sdshdr));
+	/* The sdshdr pointer has a different alignment than the original char
+	 * pointer, so cast it through a void pointer to silence the warning. */
+	return (void *)(s - (sizeof (struct sdshdr)));
 }
 
 static inline size_t sdslen(const sds s) {