Update docs and assertions

arena.h

@@ -77,6 +77,10 @@
 // Warning: this functions may cause fragmentation, consider setting an
 // appropriate region capacity.
 //
+// [Note]
+//
+// This library is not Thread-safe.
+//
 // [Example]
 //
 #if 0
@@ -171,7 +175,7 @@ Arena arena_create(size_t region_capacity)
 void *arena_alloc(Arena *a, size_t size)
 {
     if (a == NULL || size == 0) {
-        ARENA_ASSERT(!"Invalid, parameters");
+        ARENA_ASSERT(false && "Invalid, parameters");
         return NULL;
     }
 
@@ -185,7 +189,7 @@ void *arena_alloc(Arena *a, size_t size)
                 NULL, sizeof(*a->head) + alloc_size);
 
         if (a->head == NULL) {
-            ARENA_ASSERT(!"Reallocation failed");
+            ARENA_ASSERT(false && "Reallocation failed");
             return NULL;
         }
 
@@ -213,7 +217,7 @@ void *arena_alloc(Arena *a, size_t size)
                     NULL, sizeof(*a->tail) + alloc_size);
 
             if (a->tail->next == NULL) {
-                ARENA_ASSERT(!"Reallocation failed");
+                ARENA_ASSERT(false && "Reallocation failed");
                 return NULL;
             }