pthread: add pthread_getattr_np.

non standard extension, but widely available to obtain attributes for a thread.
also provides an alias for pthread_getattr_np which is the bsd equivalent.

Change-Id: I26ef8245ed2537186f48c8b8bdf3e42b03e70892
Reviewed-on: https://review.haiku-os.org/c/1172
Reviewed-by: Adrien Destugues <pulkomandy@gmail.com>

headers/compatibility/gnu/pthread.h

@@ -0,0 +1,32 @@
+/*
+ * Copyright 2019 Haiku, Inc. All Rights Reserved.
+ * Distributed under the terms of the Haiku License.
+ */
+#ifndef _GNU_PTHREAD_H_
+#define _GNU_PTHREAD_H_
+
+
+#include_next <pthread.h>
+
+
+#ifdef _GNU_SOURCE
+
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+extern int pthread_getattr_np(pthread_t thread, pthread_attr_t* attr);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+
+#endif
+
+
+#endif	/* _GNU_PTHREAD_H_ */
+

src/system/libroot/posix/pthread/pthread_attr.c

@@ -14,9 +14,13 @@
 
 #include <Debug.h>
 
+#include <syscalls.h>
 #include <thread_defs.h>
 
 
+int __pthread_getattr_np(pthread_t thread, pthread_attr_t *_attr);
+
+
 int
 pthread_attr_init(pthread_attr_t *_attr)
 {
@@ -235,3 +239,35 @@ pthread_attr_setstack(pthread_attr_t *_attr, void *stackaddr,
 	return 0;
 }
 
+
+int
+__pthread_getattr_np(pthread_t thread, pthread_attr_t *_attr)
+{
+	pthread_attr *attr;
+	status_t status;
+	thread_info info;
+
+	if (_attr == NULL || (attr = *_attr) == NULL)
+		return B_BAD_VALUE;
+
+	status = _kern_get_thread_info(thread->id, &info);
+	if (status == B_BAD_THREAD_ID)
+		return ESRCH;
+
+	if ((thread->flags & THREAD_DETACHED) != 0)
+		attr->detach_state = PTHREAD_CREATE_DETACHED;
+	else
+		attr->detach_state = PTHREAD_CREATE_JOINABLE;
+	attr->sched_priority = info.priority;
+	attr->stack_address = info.stack_base;
+	attr->stack_size = (size_t)info.stack_end - (size_t)info.stack_base;
+	// not in thread_info
+	attr->guard_size = 0;
+
+	return 0;
+}
+
+
+B_DEFINE_WEAK_ALIAS(__pthread_getattr_np, pthread_getattr_np);
+B_DEFINE_WEAK_ALIAS(__pthread_getattr_np, pthread_attr_get_np);
+