add latch macros and use them for registering plugins

Author: QuietMisdreavus

extensions/core-extensions.c

@@ -8,29 +8,20 @@
 #include "registry.h"
 #include "plugin.h"
 
-CMARK_DEFINE_LOCK(extensions);
-
 static int core_extensions_registration(cmark_plugin *plugin) {
-  CMARK_INITIALIZE_AND_LOCK(extensions);
   cmark_plugin_register_syntax_extension(plugin, create_table_extension());
   cmark_plugin_register_syntax_extension(plugin,
                                          create_strikethrough_extension());
   cmark_plugin_register_syntax_extension(plugin, create_autolink_extension());
   cmark_plugin_register_syntax_extension(plugin, create_tagfilter_extension());
   cmark_plugin_register_syntax_extension(plugin, create_tasklist_extension());
-  CMARK_UNLOCK(extensions);
   return 1;
 }
 
-pthread_mutex_t registered_lock;
-static atomic_int registered_latch = 0;
-static _Atomic int registered = 0;
+CMARK_DEFINE_LATCH(registered);
 
 void cmark_gfm_core_extensions_ensure_registered(void) {
-  CMARK_INITIALIZE_AND_LOCK(extensions);
-  if (!registered) {
+  if (CMARK_CHECK_LATCH(registered)) {
     cmark_register_plugin(core_extensions_registration);
-    registered = 1;
   }
-  CMARK_UNLOCK(extensions);
 }

src/include/mutex.h

@@ -8,10 +8,17 @@
 #include <pthread.h>
 #include <stdatomic.h>
 
-static CMARK_INLINE void initialize_mutex_once(pthread_mutex_t *m, atomic_int *latch) {
+static CMARK_INLINE bool check_latch(atomic_int *latch) {
   int expected = 0;
-  
   if (atomic_compare_exchange_strong(latch, &expected, 1)) {
+    return true;
+  } else {
+    return false;
+  }
+}
+
+static CMARK_INLINE void initialize_mutex_once(pthread_mutex_t *m, atomic_int *latch) {
+  if (check_latch(latch)) {
     pthread_mutex_init(m, NULL);
   }
 }
@@ -26,12 +33,29 @@ pthread_mutex_lock(&NAME##_lock);
 
 #define CMARK_UNLOCK(NAME) pthread_mutex_unlock(&NAME##_lock);
 
+#define CMARK_DEFINE_LATCH(NAME) static atomic_int NAME = 0;
+
+#define CMARK_CHECK_LATCH(NAME) check_latch(&NAME)
+
 #else // no threading support
 
+static CMARK_INLINE bool check_latch(int *latch) {
+  if (!*latch) {
+    *latch = 1;
+    return true;
+  } else {
+    return false;
+  }
+}
+
 #define CMARK_DEFINE_LOCK(NAME)
 #define CMARK_INITIALIZE_AND_LOCK(NAME)
 #define CMARK_UNLOCK(NAME)
 
+#define CMARK_DEFINE_LATCH static int NAME = 0;
+
+#define CMARK_CHECK_LATCH check_latch(&NAME)
+
 #endif // CMARK_THREADING
 
 #endif // CMARK_MUTEX_H