codegen: Adjust format-index for printf/scanf-methods which throw errors

If there is no explicit FormatArg annotation while this method throws an
error, it is required to mark the parameter located right before ellipsis
as format-arg to account for the parameter shifting caused by the inserted
GError parameter.

https://bugzilla.gnome.org/show_bug.cgi?id=781061

3 files changed, 45 insertions, 1 deletions

diff --git a/codegen/valaccodemethodmodule.vala b/codegen/valaccodemethodmodule.vala
index 744bf7d6e..4efd04b72 100644
--- a/codegen/valaccodemethodmodule.vala
+++ b/codegen/valaccodemethodmodule.vala
@@ -1008,6 +1008,9 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
 			}
 		}
 
+		var needs_format_arg = m.get_format_arg_index () < 0 && (m.printf_format || m.scanf_format);
+
+		CCodeParameter? prev_cparam = null;
 		foreach (Parameter param in m.get_parameters ()) {
 			if (param.direction != ParameterDirection.OUT) {
 				if ((direction & 1) == 0) {
@@ -1021,7 +1024,17 @@ public abstract class Vala.CCodeMethodModule : CCodeStructModule {
 				}
 			}
 
-			generate_parameter (param, decl_space, cparam_map, carg_map);
+			var cparam = generate_parameter (param, decl_space, cparam_map, carg_map);
+
+			// if there is no explicit FormatArg annotation while this method throws an error
+			// it is required to mark the parameter located right before ellipsis as format-arg
+			// to account for the parameter shifting caused by the inserted GError parameter
+			if (needs_format_arg) {
+				if (prev_cparam != null && cparam.ellipsis) {
+					prev_cparam.modifiers |= CCodeModifiers.FORMAT_ARG;
+				}
+				prev_cparam = cparam;
+			}
 		}
 
 		if ((direction & 2) != 0) {
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 1b1e9e955..48c0cb0eb 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -94,6 +94,7 @@ TESTS = \
 	methods/bug771964.vala \
 	methods/bug774060.vala \
 	methods/bug775466.test \
+	methods/bug781061.vala \
 	methods/generics.vala \
 	methods/printf-invalid.test \
 	methods/printf-constructor.vala \
diff --git a/tests/methods/bug781061.vala b/tests/methods/bug781061.vala
new file mode 100644
index 000000000..0969935de
--- /dev/null
+++ b/tests/methods/bug781061.vala
@@ -0,0 +1,30 @@
+errordomain FooError {
+	FAILED;
+}
+
+[PrintfFormat]
+void print_something_throws (bool ok, string format, ...) throws FooError {
+	var vargs = va_list ();
+	print_something_vargs_throws (ok, format, vargs);
+}
+
+[PrintfFormat]
+void print_something_vargs_throws (bool ok, string format, va_list vargs) throws FooError {
+}
+
+[ScanfFormat]
+void scan_something_throws (bool ok, string format, ...) throws FooError {
+}
+
+[ScanfFormat]
+void scan_something_vargs_throws (bool ok, string format, va_list vargs) throws FooError {
+}
+
+void main () {
+	try {
+		print_something_throws (true, "%s", "foo");
+		int i;
+		scan_something_throws (false, "%d", out i);
+	} catch (FooError e) {
+	}
+}