Add PYBIND11_EXPAND_SIDE_EFFECTS macro
This allows calling of functions (typically void) over a parameter
pack, replacing usage such as:
bool unused[] = { (voidfunc(param_pack_arg), false)..., false };
(void) unused;
with a much cleaner:
PYBIND11_EXPAND_SIDE_EFFECTS(voidfunc(param_pack_arg));
diff --git a/include/pybind11/common.h b/include/pybind11/common.h
index ddf966e..baa84b2 100644
--- a/include/pybind11/common.h
+++ b/include/pybind11/common.h
@@ -504,6 +504,14 @@
/// Ignore that a variable is unused in compiler warnings
inline void ignore_unused(const int *) { }
+/// Apply a function over each element of a parameter pack
+#ifdef __cpp_fold_expressions
+#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) (((PATTERN), void()), ...)
+#else
+using expand_side_effects = bool[];
+#define PYBIND11_EXPAND_SIDE_EFFECTS(PATTERN) pybind11::detail::expand_side_effects{ ((PATTERN), void(), false)..., false }
+#endif
+
NAMESPACE_END(detail)
/// Returns a named pointer that is shared among all extension modules (using the same
diff --git a/include/pybind11/pybind11.h b/include/pybind11/pybind11.h
index c4e6131..21d911c 100644
--- a/include/pybind11/pybind11.h
+++ b/include/pybind11/pybind11.h
@@ -947,8 +947,7 @@
set_operator_new<type>(&record);
/* Register base classes specified via template arguments to class_, if any */
- bool unused[] = { (add_base<options>(record), false)..., false };
- (void) unused;
+ PYBIND11_EXPAND_SIDE_EFFECTS(add_base<options>(record));
/* Process optional arguments, if any */
process_attributes<Extra...>::init(extra..., &record);