diff --git a/lib/libthr/thread/thr_attr.c b/lib/libthr/thread/thr_attr.c
--- a/lib/libthr/thread/thr_attr.c
+++ b/lib/libthr/thread/thr_attr.c
@@ -129,8 +129,9 @@
 int
 _thr_attr_get_np(pthread_t pthread, pthread_attr_t *dstattr)
 {
-	struct pthread_attr attr, *dst;
+	struct pthread_attr *dst;
 	struct pthread *curthread;
+	cpuset_t *cpuset;
 	size_t kern_size;
 	int error;
 
@@ -138,34 +139,39 @@
 		return (EINVAL);
 
 	kern_size = _get_kern_cpuset_size();
-
 	if (dst->cpuset == NULL) {
-		dst->cpuset = calloc(1, kern_size);
-		dst->cpusetsize = kern_size;
-	}
+		if ((cpuset = malloc(kern_size)) == NULL)
+			return (ENOMEM);
+	} else
+		cpuset = dst->cpuset;
 
 	curthread = _get_curthread();
 	/* Arg 0 is to include dead threads. */
-	if ((error = _thr_find_thread(curthread, pthread, 0)) != 0)
+	if ((error = _thr_find_thread(curthread, pthread, 0)) != 0) {
+		if (dst->cpuset == NULL)
+			free(cpuset);
 		return (error);
-
-	attr = pthread->attr;
-	if ((pthread->flags & THR_FLAGS_DETACHED) != 0)
-		attr.flags |= PTHREAD_DETACHED;
+	}
 
 	error = cpuset_getaffinity(CPU_LEVEL_WHICH, CPU_WHICH_TID, TID(pthread),
-	    dst->cpusetsize, dst->cpuset);
-	if (error == -1)
-		error = errno;
+	    kern_size, cpuset);
+	if (error == -1) {
+		THR_THREAD_UNLOCK(curthread, pthread);
+		return (errno);
+	}
+
+	/*
+	 * From this point on, we can't fail, so we can start modifying 'dst'.
+	 */
+
+	*dst = pthread->attr;
+	if ((pthread->flags & THR_FLAGS_DETACHED) != 0)
+		dst->flags |= PTHREAD_DETACHED;
 
 	THR_THREAD_UNLOCK(curthread, pthread);
 
-	if (error == 0)
-		memcpy(&dst->pthread_attr_start_copy,
-		    &attr.pthread_attr_start_copy,
-		    offsetof(struct pthread_attr, pthread_attr_end_copy) -
-		    offsetof(struct pthread_attr, pthread_attr_start_copy));
-
+	dst->cpuset = cpuset;
+	dst->cpusetsize = kern_size;
 	return (0);
 }
 
diff --git a/lib/libthr/thread/thr_private.h b/lib/libthr/thread/thr_private.h
--- a/lib/libthr/thread/thr_private.h
+++ b/lib/libthr/thread/thr_private.h
@@ -261,7 +261,6 @@
 };
 
 struct pthread_attr {
-#define pthread_attr_start_copy	sched_policy
 	int	sched_policy;
 	int	sched_inherit;
 	int	prio;
@@ -271,7 +270,6 @@
 	void	*stackaddr_attr;
 	size_t	stacksize_attr;
 	size_t	guardsize_attr;
-#define pthread_attr_end_copy	cpuset
 	cpuset_t	*cpuset;
 	size_t	cpusetsize;
 };