add locks around extensions registry ops

Author: QuietMisdreavus

src/registry.c

@@ -1,9 +1,11 @@
+#include <stdatomic.h>
 #include <stdint.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "cmark-gfm_config.h"
 #include "cmark-gfm.h"
+#include "mutex.h"
 #include "syntax_extension.h"
 #include "registry.h"
 #include "plugin.h"
@@ -12,6 +14,9 @@ extern cmark_mem CMARK_DEFAULT_MEM_ALLOCATOR;
 
 static cmark_llist *syntax_extensions = NULL;
 
+static pthread_mutex_t extensions_lock;
+static atomic_int extensions_latch = 0;
+
 void cmark_register_plugin(cmark_plugin_init_func reg_fn) {
   cmark_plugin *plugin = cmark_plugin_new();
 
@@ -23,41 +28,64 @@ void cmark_register_plugin(cmark_plugin_init_func reg_fn) {
   cmark_llist *syntax_extensions_list = cmark_plugin_steal_syntax_extensions(plugin),
               *it;
 
+  initialize_mutex_once(&extensions_lock, &extensions_latch);
+  pthread_mutex_lock(&extensions_lock);
+  
   for (it = syntax_extensions_list; it; it = it->next) {
     syntax_extensions = cmark_llist_append(&CMARK_DEFAULT_MEM_ALLOCATOR, syntax_extensions, it->data);
   }
+  
+  pthread_mutex_unlock(&extensions_lock);
 
   cmark_llist_free(&CMARK_DEFAULT_MEM_ALLOCATOR, syntax_extensions_list);
   cmark_plugin_free(plugin);
 }
 
 void cmark_release_plugins(void) {
+  initialize_mutex_once(&extensions_lock, &extensions_latch);
+  pthread_mutex_lock(&extensions_lock);
+  
   if (syntax_extensions) {
     cmark_llist_free_full(
         &CMARK_DEFAULT_MEM_ALLOCATOR,
         syntax_extensions,
         (cmark_free_func) cmark_syntax_extension_free);
     syntax_extensions = NULL;
   }
+  
+  pthread_mutex_unlock(&extensions_lock);
 }
 
 cmark_llist *cmark_list_syntax_extensions(cmark_mem *mem) {
   cmark_llist *it;
   cmark_llist *res = NULL;
 
+  initialize_mutex_once(&extensions_lock, &extensions_latch);
+  pthread_mutex_lock(&extensions_lock);
+  
   for (it = syntax_extensions; it; it = it->next) {
     res = cmark_llist_append(mem, res, it->data);
   }
+  
+  pthread_mutex_unlock(&extensions_lock);
   return res;
 }
 
 cmark_syntax_extension *cmark_find_syntax_extension(const char *name) {
   cmark_llist *tmp;
+  cmark_syntax_extension *res = NULL;
 
+  initialize_mutex_once(&extensions_lock, &extensions_latch);
+  pthread_mutex_lock(&extensions_lock);
+  
   for (tmp = syntax_extensions; tmp; tmp = tmp->next) {
     cmark_syntax_extension *ext = (cmark_syntax_extension *) tmp->data;
-    if (!strcmp(ext->name, name))
-      return ext;
+    if (!strcmp(ext->name, name)) {
+      res = ext;
+      break;
+    }
   }
-  return NULL;
+  
+  pthread_mutex_unlock(&extensions_lock);
+  return res;
 }