Fix or remove non-portable features in thread API

Thread function return values are inconsistent between nearly every threading
API out there.  So, just ignore them entirely, and provide a typedef and
sentinel value so user code can be portable.

3 files changed, 57 insertions, 12 deletions

diff --git a/test/test_ring.c b/test/test_ring.c
index 79aa0f1..8016910 100644
--- a/test/test_ring.c
+++ b/test/test_ring.c
@@ -43,7 +43,8 @@ cmp_msg(const int* const msg1, const int* const msg2)
   return 1;
 }
 
-static void*
+ZIX_THREAD_FUNC
+static ZixThreadResult
 reader(void* ZIX_UNUSED(arg))
 {
   printf("Reader starting\n");
@@ -63,10 +64,11 @@ reader(void* ZIX_UNUSED(arg))
   }
 
   printf("Reader finished\n");
-  return NULL;
+  return ZIX_THREAD_RESULT;
 }
 
-static void*
+ZIX_THREAD_FUNC
+static ZixThreadResult
 writer(void* ZIX_UNUSED(arg))
 {
   printf("Writer starting\n");
@@ -82,7 +84,7 @@ writer(void* ZIX_UNUSED(arg))
   }
 
   printf("Writer finished\n");
-  return NULL;
+  return ZIX_THREAD_RESULT;
 }
 
 static int
@@ -108,8 +110,8 @@ test_ring(const unsigned size)
   ZixThread writer_thread; // NOLINT
   assert(!zix_thread_create(&writer_thread, MSG_SIZE * 4UL, writer, NULL));
 
-  zix_thread_join(reader_thread, NULL);
-  zix_thread_join(writer_thread, NULL);
+  assert(!zix_thread_join(reader_thread));
+  assert(!zix_thread_join(writer_thread));
 
   assert(!read_error);
   assert(ring);
diff --git a/test/test_sem.c b/test/test_sem.c
index 33859f1..bad0a44 100644
--- a/test/test_sem.c
+++ b/test/test_sem.c
@@ -14,7 +14,8 @@
 static ZixSem   sem;
 static unsigned n_signals = 1024;
 
-static void*
+ZIX_THREAD_FUNC
+static ZixThreadResult
 reader(void* ZIX_UNUSED(arg))
 {
   printf("Reader starting\n");
@@ -24,10 +25,11 @@ reader(void* ZIX_UNUSED(arg))
   }
 
   printf("Reader finished\n");
-  return NULL;
+  return ZIX_THREAD_RESULT;
 }
 
-static void*
+ZIX_THREAD_FUNC
+static ZixThreadResult
 writer(void* ZIX_UNUSED(arg))
 {
   printf("Writer starting\n");
@@ -37,7 +39,7 @@ writer(void* ZIX_UNUSED(arg))
   }
 
   printf("Writer finished\n");
-  return NULL;
+  return ZIX_THREAD_RESULT;
 }
 
 int
@@ -62,8 +64,8 @@ main(int argc, char** argv)
   ZixThread writer_thread; // NOLINT
   assert(!zix_thread_create(&writer_thread, 128, writer, NULL));
 
-  zix_thread_join(reader_thread, NULL);
-  zix_thread_join(writer_thread, NULL);
+  assert(!zix_thread_join(reader_thread));
+  assert(!zix_thread_join(writer_thread));
 
   zix_sem_destroy(&sem);
   return 0;
diff --git a/test/test_thread.c b/test/test_thread.c
new file mode 100644
index 0000000..6fe80a5
--- /dev/null
+++ b/test/test_thread.c
@@ -0,0 +1,41 @@
+// Copyright 2012-2022 David Robillard <d@drobilla.net>
+// SPDX-License-Identifier: ISC
+
+#undef NDEBUG
+
+#include "zix/thread.h"
+
+#include <assert.h>
+#include <string.h>
+
+typedef struct {
+  int input;
+  int output;
+} SharedData;
+
+ZIX_THREAD_FUNC
+static ZixThreadResult
+thread_func(void* const arg)
+{
+  SharedData* const data = (SharedData*)arg;
+
+  data->output = data->input * 7;
+
+  return ZIX_THREAD_RESULT;
+}
+
+int
+main(int argc, char** argv)
+{
+  (void)argv;
+
+  ZixThread thread; // NOLINT
+
+  SharedData data = {argc + (int)strlen(argv[0]), 0};
+
+  assert(!zix_thread_create(&thread, 128, thread_func, &data));
+  assert(!zix_thread_join(thread));
+  assert(data.output == data.input * 7);
+
+  return 0;
+}