c variadic calls

compiler/types/types.odin

@@ -432,6 +432,34 @@ is_c_signature_type :: proc(value: Type, store: ^Store, allow_void := false) ->
 	return is_concrete_scalar(value) || is_pointer(value, store) || is_optional_pointer(value, store)
 }
 
+is_c_integer_promotion_candidate :: proc(value: Type) -> bool {
+	return value >= C_CHAR && value <= C_USHORT
+}
+
+c_vararg_promotion :: proc(value: Type, selected := target.DEFAULT) -> Type {
+	if !is_concrete_scalar(value) {
+		return value
+	}
+	if is_float(value, selected) && bits(value, selected) < bits(C_DOUBLE, selected) {
+		return C_DOUBLE
+	}
+	if is_concrete_integer(value) {
+		value_bits := bits(value, selected)
+		int_bits := bits(C_INT, selected)
+		if value_bits < int_bits {
+			return C_INT
+		}
+		if is_c_integer_promotion_candidate(value) && value_bits == int_bits {
+			return C_INT if is_signed(value, selected) else C_UINT
+		}
+	}
+	return value
+}
+
+is_c_vararg_type :: proc(value: Type, store: ^Store) -> bool {
+	return is_concrete_scalar(value) || is_pointer(value, store) || is_optional_pointer(value, store)
+}
+
 child_type :: proc(value: Type, store: ^Store) -> Type {
 	item, ok := node(store, value)
 	return item.child if ok else INVALID