fixup! sys/posix/pthread: Add pthread_attr_getstack and pthread_attr_…

…setstack

Reuse existing functions inside new functions

sys/posix/pthread/pthread_attr.c

@@ -161,18 +161,20 @@ int pthread_attr_setstacksize(pthread_attr_t *attr, size_t stacksize)
 
 int pthread_attr_getstack(pthread_attr_t *attr, void **stackaddr, size_t *stacksize)
 {
-    *stackaddr = attr->ss_sp;
-    *stacksize = attr->ss_size;
-    if (*stacksize == 0) {
-        /* FIXME: the standard says that this function should return the default
-        * value if no explicit value was set. */
+    int res = pthread_attr_getstackaddr(attr, stackaddr);
+    if (res != 0) {
+        return res;
     }
-    return 0;
+
+    return pthread_attr_getstacksize(attr, stacksize);
 }
 
 int pthread_attr_setstack(pthread_attr_t *attr, void *stackaddr, size_t stacksize)
 {
-    attr->ss_sp = (char *)stackaddr;
-    attr->ss_size = stacksize;
-    return 0;
+    int res = pthread_attr_setstackaddr(attr, stackaddr);
+    if (res != 0) {
+        return res;
+    }
+
+    return pthread_attr_setstacksize(attr, stacksize);
 }