gitypelib: Switch to refcounting

Since `GITypelib` is exposed in the public libgirepository API, it needs
to be a boxed type. So we either need to add a `copy` method to mirror
the existing `free` method, or switch to refcounting. The latter option
seems better, since a `GITypelib` contains internal state about open
`GModule`s and the semantics for copying that would be potentially
complex.

Signed-off-by: Philip Withnall <pwithnall@gnome.org>

Helps: #3155

docs/reference/girepository/migrating-gi.md

@@ -71,6 +71,7 @@ your code if integer type warnings are enabled.
 | `g_type_info_get_array_length` and `g_type_info_get_array_fixed_size` | Split success and failure return values out into a new out-argument and return value |
 | `g_type_info_get_array_length` | [method@GIRepository.TypeInfo.get_array_length_index] |
 | `g_typelib_new_from_*` | All replaced with `gi_typelib_new_from_bytes()` |
+| `g_typelib_free` | [type@GIRepository.Typelib] is now a refcounted and boxed type, so use [method@GIRepository.Typelib.unref] |
 | `GI_FUNCTION_THROWS` and `GI_VFUNC_THROWS` | [method@GIRepository.CallableInfo.can_throw_gerror] |
 | `g_union_info_get_copy_function` | [method@GIRepository.UnionInfo.get_copy_function_name] |
 | `g_union_info_get_free_function` | [method@GIRepository.UnionInfo.get_free_function_name] |

girepository/compiler/compiler.c

@@ -218,7 +218,7 @@ main (int argc, char **argv)
   g_debug ("[building] start");
 
   {
-    GITypelib *typelib;
+    GITypelib *typelib = NULL;
 
     if (shlibs)
       {
@@ -238,8 +238,8 @@ main (int argc, char **argv)
 
     if (!write_out_typelib (NULL, typelib))
       return 1;
-    gi_typelib_free (typelib);
-    typelib = NULL;
+
+    g_clear_pointer (&typelib, gi_typelib_unref);
   }
 
   g_debug ("[building] done");

girepository/girepository.c

@@ -185,11 +185,11 @@ gi_repository_init (GIRepository *repository)
   repository->typelibs
     = g_hash_table_new_full (g_str_hash, g_str_equal,
                              (GDestroyNotify) g_free,
-                             (GDestroyNotify) gi_typelib_free);
+                             (GDestroyNotify) gi_typelib_unref);
   repository->lazy_typelibs
     = g_hash_table_new_full (g_str_hash, g_str_equal,
                              (GDestroyNotify) g_free,
-                             (GDestroyNotify) NULL);
+                             (GDestroyNotify) gi_typelib_unref);
   repository->info_by_gtype
     = g_hash_table_new_full (g_direct_hash, g_direct_equal,
                              (GDestroyNotify) NULL,
@@ -513,7 +513,7 @@ register_internal (GIRepository *repository,
       g_assert (!g_hash_table_lookup (repository->lazy_typelibs,
                                       namespace));
       g_hash_table_insert (repository->lazy_typelibs,
-                           build_typelib_key (namespace, source), (void *)typelib);
+                           build_typelib_key (namespace, source), gi_typelib_ref (typelib));
     }
   else
     {
@@ -534,7 +534,7 @@ register_internal (GIRepository *repository,
 
       g_hash_table_insert (repository->typelibs,
                            g_steal_pointer (&key),
-                           (void *)typelib);
+                           gi_typelib_ref (typelib));
     }
 
   /* These types might be resolved now, clear the cache */
@@ -685,7 +685,7 @@ gi_repository_get_dependencies (GIRepository *repository,
 /**
  * gi_repository_load_typelib:
  * @repository: A #GIRepository
- * @typelib: the typelib to load
+ * @typelib: (transfer none): the typelib to load
  * @flags: flags affecting the loading operation
  * @error: return location for a [type@GLib.Error], or `NULL`
  *
@@ -1706,6 +1706,7 @@ require_internal (GIRepository           *repository,
   GITypelib *ret = NULL;
   Header *header;
   GITypelib *typelib = NULL;
+  GITypelib *typelib_owned = NULL;
   const char *typelib_namespace, *typelib_version;
   gboolean allow_lazy = (flags & GI_REPOSITORY_LOAD_FLAG_LAZY) > 0;
   gboolean is_lazy;
@@ -1762,7 +1763,7 @@ require_internal (GIRepository           *repository,
     GBytes *bytes = NULL;
 
     bytes = g_mapped_file_get_bytes (mfile);
-    typelib = gi_typelib_new_from_bytes (bytes, &temp_error);
+    typelib_owned = typelib = gi_typelib_new_from_bytes (bytes, &temp_error);
     g_bytes_unref (bytes);
     g_clear_pointer (&mfile, g_mapped_file_unref);
 
@@ -1789,7 +1790,6 @@ require_internal (GIRepository           *repository,
                    "Typelib file %s for namespace '%s' contains "
                    "namespace '%s' which doesn't match the file name",
                    path, namespace, typelib_namespace);
-      gi_typelib_free (typelib);
       goto out;
     }
   if (version != NULL && strcmp (typelib_version, version) != 0)
@@ -1799,18 +1799,15 @@ require_internal (GIRepository           *repository,
                    "Typelib file %s for namespace '%s' contains "
                    "version '%s' which doesn't match the expected version '%s'",
                    path, namespace, typelib_version, version);
-      gi_typelib_free (typelib);
       goto out;
     }
 
   if (!register_internal (repository, path, allow_lazy,
                           typelib, error))
-    {
-      gi_typelib_free (typelib);
     goto out;
-    }
   ret = typelib;
  out:
+  g_clear_pointer (&typelib_owned, gi_typelib_unref);
   g_free (tmp_version);
   g_free (path);
   return ret;

girepository/gitypelib-internal.h

@@ -1313,6 +1313,7 @@ typedef struct {
 
 struct _GITypelib {
   /*< private >*/
+  gatomicrefcount ref_count;
   const uint8_t *data;  /* just a cached pointer to inside @bytes */
   size_t len;
   GBytes *bytes;  /* (owned) */

girepository/gitypelib.c

@@ -2353,6 +2353,7 @@ gi_typelib_new_from_bytes (GBytes *bytes,
     return NULL;
 
   meta = g_slice_new0 (GITypelib);
+  g_atomic_ref_count_init (&meta->ref_count);
   meta->bytes = g_bytes_ref (bytes);
   meta->data = data;
   meta->len = len;
@@ -2362,15 +2363,40 @@ gi_typelib_new_from_bytes (GBytes *bytes,
 }
 
 /**
- * gi_typelib_free:
+ * gi_typelib_ref:
+ * @typelib: (transfer none): a #GITypelib
+ *
+ * Increment the reference count of a [type@GIRepository.Typelib].
+ *
+ * Returns: (transfer full): the same @typelib pointer
+ * Since: 2.80
+ */
+GITypelib *
+gi_typelib_ref (GITypelib *typelib)
+{
+  g_return_val_if_fail (typelib != NULL, NULL);
+
+  g_atomic_ref_count_inc (&typelib->ref_count);
+
+  return typelib;
+}
+
+/**
+ * gi_typelib_unref:
  * @typelib: (transfer full): a #GITypelib
  *
- * Free a [type@GIRepository.Typelib].
+ * Decrement the reference count of a [type@GIRepository.Typelib].
+ *
+ * Once the reference count reaches zero, the typelib is freed.
  *
  * Since: 2.80
  */
 void
-gi_typelib_free (GITypelib *typelib)
+gi_typelib_unref (GITypelib *typelib)
+{
+  g_return_if_fail (typelib != NULL);
+
+  if (g_atomic_ref_count_dec (&typelib->ref_count))
     {
       g_clear_pointer (&typelib->bytes, g_bytes_unref);
 
@@ -2383,6 +2409,7 @@ gi_typelib_free (GITypelib *typelib)
         }
       g_slice_free (GITypelib, typelib);
     }
+}
 
 /**
  * gi_typelib_get_namespace:

girepository/gitypelib.h

@@ -41,7 +41,9 @@ GITypelib *    gi_typelib_new_from_bytes       (GBytes  *bytes,
                                                 GError **error);
 
 GI_AVAILABLE_IN_ALL
-void          gi_typelib_free                  (GITypelib     *typelib);
+GITypelib *   gi_typelib_ref                   (GITypelib     *typelib);
+GI_AVAILABLE_IN_ALL
+void          gi_typelib_unref                 (GITypelib     *typelib);
 
 GI_AVAILABLE_IN_ALL
 gboolean      gi_typelib_symbol                (GITypelib     *typelib,