Improve the implementation and documentation of the

SYSCTL_COUNTER_U64_ARRAY() macro.

- Add proper asserts to the SYSCTL_COUNTER_U64_ARRAY() macro that checks
  the size of the first element of the array.
- Add an example to the counter(9) manual page how to use the
  SYSCTL_COUNTER_U64_ARRAY() macro.
- Add some missing symbolic links for counter(9) while at it.

3 files changed, 19 insertions, 3 deletions

diff --git a/share/man/man9/Makefile b/share/man/man9/Makefile
index 66c16d7..26f230c 100644
--- a/share/man/man9/Makefile
+++ b/share/man/man9/Makefile
@@ -639,7 +639,11 @@ MLINKS+=counter.9 counter_u64_alloc.9 \
 	counter.9 counter_exit.9 \
 	counter.9 counter_u64_add_protected.9 \
 	counter.9 counter_u64_fetch.9 \
-	counter.9 counter_u64_zero.9
+	counter.9 counter_u64_zero.9 \
+	counter.9 SYSCTL_COUNTER_U64.9 \
+	counter.9 SYSCTL_ADD_COUNTER_U64.9 \
+	counter.9 SYSCTL_COUNTER_U64_ARRAY.9 \
+	counter.9 SYSCTL_ADD_COUNTER_U64_ARRAY.9
 MLINKS+=cpuset.9 CPUSET_T_INITIALIZER.9 \
 	cpuset.9 CPUSET_FSET.9 \
 	cpuset.9 CPU_CLR.9 \
diff --git a/share/man/man9/counter.9 b/share/man/man9/counter.9
index 85bc9fe..0fcf2ad 100644
--- a/share/man/man9/counter.9
+++ b/share/man/man9/counter.9
@@ -215,6 +215,16 @@ amd64 single-instruction implementation.
 On some architectures updating a counter require a
 .Xr critical 9
 section.
+.Sh EXAMPLES
+The following example creates a static counter array exported to
+userspace through a sysctl:
+.Bd -literal -offset indent
+#define MY_SIZE 8
+static counter_u64_t array[MY_SIZE];
+SYSCTL_COUNTER_U64_ARRAY(_debug, OID_AUTO, counter_array, CTLFLAG_RW,
+    &array[0], MY_SIZE, "Test counter array");
+.Ed
+.Pp
 .Sh SEE ALSO
 .Xr atomic 9 ,
 .Xr critical 9 ,
diff --git a/sys/sys/sysctl.h b/sys/sys/sysctl.h
index 34ee03c..eb5eef0 100644
--- a/sys/sys/sysctl.h
+++ b/sys/sys/sysctl.h
@@ -654,8 +654,10 @@ TAILQ_HEAD(sysctl_ctx_list, sysctl_ctx_entry);
 	SYSCTL_OID(parent, nbr, name,					\
 	    CTLTYPE_OPAQUE | CTLFLAG_MPSAFE | (access),			\
 	    (ptr), (len), sysctl_handle_counter_u64_array, "S", descr);	\
-	CTASSERT(((access) & CTLTYPE) == 0 ||				\
-	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_OPAQUE)
+	CTASSERT((((access) & CTLTYPE) == 0 ||				\
+	    ((access) & SYSCTL_CT_ASSERT_MASK) == CTLTYPE_OPAQUE) &&	\
+	    sizeof(counter_u64_t) == sizeof(*(ptr)) &&			\
+	    sizeof(uint64_t) == sizeof(**(ptr)))
 
 #define	SYSCTL_ADD_COUNTER_U64_ARRAY(ctx, parent, nbr, name, access,	\
     ptr, len, descr)							\