@@ -12,10 +12,13 @@
  * Alternatively, it may be distributed under the terms of the GNU General
  * Public License, either version 2 or 3, which can be found in the file
  * LICENSE.GPLv2 or LICENSE.GPLv3 respectively included in the packaging of this
  * file.
  */
+
+#include <assert.h>
+#include <errno.h>
 
 #include <dos/dostags.h>
 #include <proto/dos.h>
 #include <proto/exec.h>
 
@@ -72,12 +75,14 @@
 of_thread_new(of_thread_t *thread, void (*function)(id), id object,
     const of_thread_attr_t *attr)
 {
 	OFMutableData *tags = nil;
 
-	if ((*thread = calloc(1, sizeof(**thread))) == NULL)
+	if ((*thread = calloc(1, sizeof(**thread))) == NULL) {
+		errno = ENOMEM;
 		return false;
+	}
 
 	@try {
 		(*thread)->function = function;
 		(*thread)->object = object;
 		InitSemaphore(&(*thread)->semaphore);
@@ -108,12 +113,14 @@
 		ADD_TAG(NP_CloseInput, FALSE)
 		ADD_TAG(NP_CloseOutput, FALSE)
 		ADD_TAG(NP_CloseError, FALSE)
 
 		if (attr != NULL && attr->priority != 0) {
-			if (attr->priority < 1 || attr->priority > 1)
+			if (attr->priority < 1 || attr->priority > 1) {
+				errno = EINVAL;
 				return false;
+			}
 
 			/*
 			 * -1 should be -128 (lowest possible priority) while
 			 * +1 should be +127 (highest possible priority).
 			 */
@@ -131,10 +138,11 @@
 #undef ADD_TAG
 
 		(*thread)->task = (struct Task *)CreateNewProc(tags.items);
 		if ((*thread)->task == NULL) {
 			free(*thread);
+			errno = EAGAIN;
 			return false;
 		}
 	} @catch (id e) {
 		free(*thread);
 		@throw e;
@@ -152,37 +160,39 @@
 }
 
 bool
 of_thread_join(of_thread_t thread)
 {
-	bool ret;
-
 	ObtainSemaphore(&thread->semaphore);
 	@try {
 		if (thread->done) {
 			free(thread);
 			return true;
 		}
 
-		if (thread->detached || thread->joinTask != NULL)
+		if (thread->detached || thread->joinTask != NULL) {
+			errno = EINVAL;
 			return false;
+		}
 
-		if ((thread->joinSigBit = AllocSignal(-1)) == -1)
+		if ((thread->joinSigBit = AllocSignal(-1)) == -1) {
+			errno = EAGAIN;
 			return false;
+		}
 
 		thread->joinTask = FindTask(NULL);
 	} @finally {
 		ReleaseSemaphore(&thread->semaphore);
 	}
 
-	Wait(1 << thread->joinSigBit);
+	Wait(1ul << thread->joinSigBit);
 	FreeSignal(thread->joinSigBit);
 
-	ret = thread->done;
+	assert(thread->done);
 	free(thread);
 
-	return ret;
+	return true;
 }
 
 bool
 of_thread_detach(of_thread_t thread)
 {