Module Name: src
Committed By: christos
Date: Sat Nov 23 14:41:38 UTC 2013
Modified Files:
src/sys/sys: queue.h
Log Message:
Add __launder_type() from mrg to get the CIRCLEQ macros working again under
gcc-4.8. Mention that we discourage their use and that we retain the macros
for compatibility only.
To generate a diff of this commit:
cvs rdiff -u -r1.57 -r1.58 src/sys/sys/queue.h
Please note that diffs are not public domain; they are subject to the
copyright notices on the relevant files.
Modified files:
Index: src/sys/sys/queue.h
diff -u src/sys/sys/queue.h:1.57 src/sys/sys/queue.h:1.58
--- src/sys/sys/queue.h:1.57 Thu Nov 21 14:04:19 2013
+++ src/sys/sys/queue.h Sat Nov 23 09:41:38 2013
@@ -1,4 +1,4 @@
-/* $NetBSD: queue.h,v 1.57 2013/11/21 19:04:19 christos Exp $ */
+/* $NetBSD: queue.h,v 1.58 2013/11/23 14:41:38 christos Exp $ */
/*
* Copyright (c) 1991, 1993
@@ -600,8 +600,29 @@ struct { \
/*
- * Circular queue definitions.
+ * Circular queue definitions. Do not use. We still keep the macros
+ * for compatibility but because of pointer aliasing issues their use
+ * is discouraged!
*/
+
+/*
+ * We use this ugly hack to work around the fact that the CIRCLEQ
+ * macros violate the C aliasing rules by comparing 'struct name *'
+ * and 'struct type *' (see CIRCLEQ_HEAD() below). Modern compilers
+ * (such as GCC 4.8) declare this to be always false and this makes
+ * most of the macros below not function correctly.
+ *
+ * This hack is only to be used for comparisons and thus can be
+ * fully const. Do not use for assignment.
+ */
+static inline const void * __launder_type(const void *x);
+static inline const void *
+__launder_type(const void *x)
+{
+ __asm volatile("" : "+r" (x));
+ return x;
+}
+
#if defined(_KERNEL) && defined(QUEUEDEBUG)
#define QUEUEDEBUG_CIRCLEQ_HEAD(head, field) \
if ((head)->cqh_first != CIRCLEQ_ENDC(head) && \
@@ -609,11 +630,11 @@ struct { \
panic("CIRCLEQ head forw %p %s:%d", (head), \
__FILE__, __LINE__); \
if ((head)->cqh_last != CIRCLEQ_ENDC(head) && \
- (head)->cqh_last->field.cqe_next != CIRCLEQ_ENDC(head)) \
+ (head)->cqh_last->field.cqe_next != CIRCLEQ_ENDC(head)) \
panic("CIRCLEQ head back %p %s:%d", (head), \
__FILE__, __LINE__);
#define QUEUEDEBUG_CIRCLEQ_ELM(head, elm, field) \
- if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) { \
+ if ((elm)->field.cqe_next == CIRCLEQ_ENDC(head)) { \
if ((head)->cqh_last != (elm)) \
panic("CIRCLEQ elm last %p %s:%d", (elm), \
__FILE__, __LINE__); \
@@ -622,7 +643,7 @@ struct { \
panic("CIRCLEQ elm forw %p %s:%d", (elm), \
__FILE__, __LINE__); \
} \
- if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) { \
+ if ((elm)->field.cqe_prev == CIRCLEQ_ENDC(head)) { \
if ((head)->cqh_first != (elm)) \
panic("CIRCLEQ elm first %p %s:%d", (elm), \
__FILE__, __LINE__); \
@@ -741,7 +762,7 @@ struct { \
#define CIRCLEQ_FIRST(head) ((head)->cqh_first)
#define CIRCLEQ_LAST(head) ((head)->cqh_last)
/* For comparisons */
-#define CIRCLEQ_ENDC(head) ((const void *)(head))
+#define CIRCLEQ_ENDC(head) (__launder_type(head))
/* For assignments */
#define CIRCLEQ_END(head) ((void *)(head))
#define CIRCLEQ_NEXT(elm, field) ((elm)->field.cqe_next)
