From 4d0d7cbccec1c35f544f6fee24b762e398a2f0b9 Mon Sep 17 00:00:00 2001 From: Mathieu Desnoyers Date: Mon, 7 Mar 2016 19:24:20 -0500 Subject: [PATCH] wfcqueue: add C++ compatibility API Introduce __cds_wfcq_head_cast and cds_wfcq_head_cast for compability of wfcqueue with c++. Those are effect-less in C, where transparent unions are supported. However, in C++, those transform struct cds_wfcq_head and struct __cds_wfcq_head pointers to cds_wfcq_head_ptr_t. Reviewed-by: Paul E. McKenney Tested-by: Paul E. McKenney Signed-off-by: Mathieu Desnoyers --- urcu/static/wfcqueue.h | 16 +++++++++------- urcu/wfcqueue.h | 40 ++++++++++++++++++++++++++++++++++++++++ 2 files changed, 49 insertions(+), 7 deletions(-) diff --git a/urcu/static/wfcqueue.h b/urcu/static/wfcqueue.h index 7c9d548..4ababbf 100644 --- a/urcu/static/wfcqueue.h +++ b/urcu/static/wfcqueue.h @@ -257,7 +257,7 @@ ___cds_wfcq_first(cds_wfcq_head_ptr_t u_head, struct __cds_wfcq_head *head = u_head._h; struct cds_wfcq_node *node; - if (_cds_wfcq_empty(head, tail)) + if (_cds_wfcq_empty(__cds_wfcq_head_cast(head), tail)) return NULL; node = ___cds_wfcq_node_sync_next(&head->node, blocking); /* Load head->node.next before loading node's content */ @@ -375,7 +375,7 @@ ___cds_wfcq_dequeue_with_state(cds_wfcq_head_ptr_t u_head, if (state) *state = 0; - if (_cds_wfcq_empty(head, tail)) { + if (_cds_wfcq_empty(__cds_wfcq_head_cast(head), tail)) { return NULL; } @@ -509,7 +509,7 @@ ___cds_wfcq_splice( * Initial emptiness check to speed up cases where queue is * empty: only require loads to check if queue is empty. */ - if (_cds_wfcq_empty(src_q_head, src_q_tail)) + if (_cds_wfcq_empty(__cds_wfcq_head_cast(src_q_head), src_q_tail)) return CDS_WFCQ_RET_SRC_EMPTY; for (;;) { @@ -539,7 +539,8 @@ ___cds_wfcq_splice( * Append the spliced content of src_q into dest_q. Does not * require mutual exclusion on dest_q (wait-free). */ - if (___cds_wfcq_append(dest_q_head, dest_q_tail, head, tail)) + if (___cds_wfcq_append(__cds_wfcq_head_cast(dest_q_head), dest_q_tail, + head, tail)) return CDS_WFCQ_RET_DEST_NON_EMPTY; else return CDS_WFCQ_RET_DEST_EMPTY; @@ -599,7 +600,8 @@ _cds_wfcq_dequeue_with_state_blocking(struct cds_wfcq_head *head, struct cds_wfcq_node *retval; _cds_wfcq_dequeue_lock(head, tail); - retval = ___cds_wfcq_dequeue_with_state_blocking(head, tail, state); + retval = ___cds_wfcq_dequeue_with_state_blocking(cds_wfcq_head_cast(head), + tail, state); _cds_wfcq_dequeue_unlock(head, tail); return retval; } @@ -638,8 +640,8 @@ _cds_wfcq_splice_blocking( enum cds_wfcq_ret ret; _cds_wfcq_dequeue_lock(src_q_head, src_q_tail); - ret = ___cds_wfcq_splice_blocking(dest_q_head, dest_q_tail, - src_q_head, src_q_tail); + ret = ___cds_wfcq_splice_blocking(cds_wfcq_head_cast(dest_q_head), dest_q_tail, + cds_wfcq_head_cast(src_q_head), src_q_tail); _cds_wfcq_dequeue_unlock(src_q_head, src_q_tail); return ret; } diff --git a/urcu/wfcqueue.h b/urcu/wfcqueue.h index c0bb289..ec86032 100644 --- a/urcu/wfcqueue.h +++ b/urcu/wfcqueue.h @@ -74,6 +74,7 @@ struct cds_wfcq_head { pthread_mutex_t lock; }; +#ifndef __cplusplus /* * The transparent union allows calling functions that work on both * struct cds_wfcq_head and struct __cds_wfcq_head on any of those two @@ -84,6 +85,45 @@ typedef union { struct cds_wfcq_head *h; } __attribute__((__transparent_union__)) cds_wfcq_head_ptr_t; +/* + * This static inline is only present for compatibility with C++. It is + * effect-less in C. + */ +static inline struct __cds_wfcq_head *__cds_wfcq_head_cast(struct __cds_wfcq_head *head) +{ + return head; +} + +/* + * This static inline is only present for compatibility with C++. It is + * effect-less in C. + */ +static inline struct cds_wfcq_head *cds_wfcq_head_cast(struct cds_wfcq_head *head) +{ + return head; +} +#else /* #ifndef __cplusplus */ + +/* C++ ignores transparent union. */ +typedef union { + struct __cds_wfcq_head *_h; + struct cds_wfcq_head *h; +} cds_wfcq_head_ptr_t; + +/* C++ ignores transparent union. Requires an explicit conversion. */ +static inline cds_wfcq_head_ptr_t __cds_wfcq_head_cast(struct __cds_wfcq_head *head) +{ + cds_wfcq_head_ptr_t ret = { ._h = head }; + return ret; +} +/* C++ ignores transparent union. Requires an explicit conversion. */ +static inline cds_wfcq_head_ptr_t cds_wfcq_head_cast(struct cds_wfcq_head *head) +{ + cds_wfcq_head_ptr_t ret = { .h = head }; + return ret; +} +#endif /* #else #ifndef __cplusplus */ + struct cds_wfcq_tail { struct cds_wfcq_node *p; }; -- 2.34.1