Add comment for always_false

pybind · Dec 21, 2024 · 921657a · 921657a
1 parent 9d46b4d
commit 921657a
Showing 1 changed file with 5 additions and 0 deletions.
diff --git a/include/pybind11/detail/common.h b/include/pybind11/detail/common.h
@@ -627,6 +627,11 @@ struct instance {
 static_assert(std::is_standard_layout<instance>::value,
               "Internal error: `pybind11::detail::instance` is not standard layout!");
 
+// Some older compilers (e.g. gcc 9.4.0) require
+//     static_assert(always_false<T>::value, "...");
+// instead of
+//     static_assert(false, "...");
+// to trigger the static_assert() in a template only if it is actually instantiated.
 template <typename>
 struct always_false : std::false_type {};