[gjs] arg: Ignore compiler warning on un-initialized value

[Philip Chimento <pchimento src gnome org>]

commit 1f8bc1f121f3afb2002e2294a3bb38f5d29e9e4c
Author: Marco Trevisan (Treviño) <mail 3v1n0 net>
Date:   Tue May 12 12:49:08 2020 +0200

    arg: Ignore compiler warning on un-initialized value
    
    We're quite sure we do, otherwise we'd have already returned false but
    g++ isn't smart enough to catch it, when building with release optimizations.

 gi/arg.cpp | 9 +++++++++
 1 file changed, 9 insertions(+)
---
diff --git a/gi/arg.cpp b/gi/arg.cpp
index 2097acd8..b53ff7f4 100644
--- a/gi/arg.cpp
+++ b/gi/arg.cpp
@@ -748,7 +748,16 @@ gjs_object_to_g_hash(JSContext   *context,
                                                               &val_arg);
         }
 
+#if __GNUC__ >= 8  // clang-format off
+_Pragma("GCC diagnostic push")
+_Pragma("GCC diagnostic ignored \"-Wmaybe-uninitialized\"")
+#endif
+        // The compiler isn't smart enough to figure out that key_ptr will
+        // always be initialized if value_to_ghashtable_key() returns true.
         g_hash_table_insert(result, key_ptr, val_ptr);
+#if __GNUC__ >= 8
+_Pragma("GCC diagnostic pop")
+#endif  // clang-format on
     }
 
     *hash_p = result.release();