clang-plugin: Fix diagnostics to correctly use format placeholders

7 files changed, 207 insertions, 287 deletions

diff --git a/clang-plugin/debug.cpp b/clang-plugin/debug.cpp
index 7a37058..21b0468 100644
--- a/clang-plugin/debug.cpp
+++ b/clang-plugin/debug.cpp
@@ -29,7 +29,7 @@ using namespace clang;
 
 /* Build and emit a warning or error report about the user’s code. */
 DiagnosticBuilder
-Debug::emit_report (DiagnosticsEngine::Level level, const std::string& message,
+Debug::emit_report (DiagnosticsEngine::Level level, const char *format_string,
                     CompilerInstance& compiler, SourceLocation location)
 {
 	DiagnosticsEngine& engine = compiler.getDiagnostics ();
@@ -43,31 +43,33 @@ Debug::emit_report (DiagnosticsEngine::Level level, const std::string& message,
 	    engine.getErrorsAsFatal ())
 		level = DiagnosticsEngine::Fatal;
 
-	const std::string prefixed_message = "[tartan]: " + message;
+	/* Add a prefix. */
+	std::string prefixed_format_string =
+		"[tartan]: " + std::string (format_string);
+
+	unsigned diag_id = engine.getCustomDiagID (level,
+	                                           prefixed_format_string);
 
 	if (!location.isValid ()) {
-		return engine.Report (engine.getCustomDiagID (level,
-		                                              prefixed_message));
+		return engine.Report (diag_id);
 	}
 
-	return engine.Report (location,
-	                      engine.getCustomDiagID (level,
-	                                              prefixed_message));
+	return engine.Report (location, diag_id);
 }
 
 /* Convenience wrappers. */
 DiagnosticBuilder
-Debug::emit_error (const std::string& message, CompilerInstance& compiler,
+Debug::emit_error (const char *format_string, CompilerInstance& compiler,
                    SourceLocation location)
 {
-	return Debug::emit_report (DiagnosticsEngine::Error, message,
+	return Debug::emit_report (DiagnosticsEngine::Error, format_string,
 	                           compiler, location);
 }
 
 DiagnosticBuilder
-Debug::emit_warning (const std::string& message, CompilerInstance& compiler,
+Debug::emit_warning (const char *format_string, CompilerInstance& compiler,
                      SourceLocation location)
 {
-	return Debug::emit_report (DiagnosticsEngine::Warning, message,
+	return Debug::emit_report (DiagnosticsEngine::Warning, format_string,
 	                           compiler, location);
 }
diff --git a/clang-plugin/debug.h b/clang-plugin/debug.h
index ddd211f..ffa7437 100644
--- a/clang-plugin/debug.h
+++ b/clang-plugin/debug.h
@@ -47,13 +47,13 @@ namespace Debug {
 	llvm::errs () << "\n"
 
 	DiagnosticBuilder emit_report (DiagnosticsEngine::Level level,
-	                               const std::string& message,
+	                               const char *format_string,
 	                               CompilerInstance& compiler,
 	                               SourceLocation location);
-	DiagnosticBuilder emit_error (const std::string& message,
+	DiagnosticBuilder emit_error (const char *format_string,
 	                              CompilerInstance& compiler,
 	                              SourceLocation location);
-	DiagnosticBuilder emit_warning (const std::string& message,
+	DiagnosticBuilder emit_warning (const char *format_string,
 	                                CompilerInstance& compiler,
 	                                SourceLocation location);
 }
diff --git a/clang-plugin/gir-attributes.cpp b/clang-plugin/gir-attributes.cpp
index 96b2be4..a6ac027 100644
--- a/clang-plugin/gir-attributes.cpp
+++ b/clang-plugin/gir-attributes.cpp
@@ -421,22 +421,22 @@ GirAttributesChecker::_handle_function_decl (FunctionDecl& func)
 		    return_transfer != GI_TRANSFER_NOTHING) {
 			Debug::emit_error (
 				"Missing (transfer none) annotation on the "
-				"return value of function " +
-				func.getNameAsString () + "() "
-				"(already has a const modifier).",
+				"return value of function %0() (already has a "
+				"const modifier).",
 				this->_compiler,
-				func.getLocStart ());
+				func.getLocStart ())
+			<< func.getNameAsString ();
 		} else if (return_transfer == GI_TRANSFER_NOTHING &&
 		           _type_should_be_const (return_transfer,
 		                                  return_type_tag) &&
 		           !_function_return_type_is_const (func)) {
 			Debug::emit_error (
 				"Missing const modifier on the return value of "
-				"function " +
-				func.getNameAsString () + "() "
-				"(already has a (transfer none) annotation).",
+				"function %0() (already has a (transfer none) "
+				"annotation).",
 				this->_compiler,
-				func.getLocStart ());
+				func.getLocStart ())
+			<< func.getNameAsString ();
 		}
 
 		break;
diff --git a/clang-plugin/gsignal-checker.cpp b/clang-plugin/gsignal-checker.cpp
index 1855075..b289395 100644
--- a/clang-plugin/gsignal-checker.cpp
+++ b/clang-plugin/gsignal-checker.cpp
@@ -465,22 +465,17 @@ _check_signal_callback_type (const Expr *expr,
 
 		if (value_type->isFunctionNoProtoType ()) {
 			/* Warning. */
-			gchar *error;
 
 			/* TODO: Emit expected type of signal callback? */
-			std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-			error = g_strdup_printf ("Could not check type of "
-			                         "handler for signal "
-			                         "‘%s::%s’. Callback function "
-			                         "declaration does not contain "
-			                         "parameter types.",
-			                         c_type.c_str (),
-			                         g_base_info_get_name (signal_info));
-			Debug::emit_warning (error, compiler, expr->getLocStart ())
+			Debug::emit_warning ("Could not check type of handler "
+			                     "for signal ‘%0::%1’. Callback "
+			                     "function declaration does not "
+			                     "contain parameter types.",
+			                     compiler, expr->getLocStart ())
+			<< gir_manager.get_c_name_for_type (static_gobject_info)
+			<< g_base_info_get_name (signal_info)
 			<< decl_range;
 
-			g_free (error);
-
 			return false;
 		} else if (!value_type->isFunctionProtoType ()) {
 			/* Error. */
@@ -533,21 +528,18 @@ _check_signal_callback_type (const Expr *expr,
 
 	if (n_args != callback_type->getNumArgs ()) {
 		/* Error. */
-		gchar *error;
 
 		/* TODO: Emit expected type of signal callback? */
-		std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-		error = g_strdup_printf ("Incorrect number of arguments in "
-		                         "signal handler for signal "
-		                         "‘%s::%s’. Expected %u but saw %u.",
-		                         c_type.c_str (),
-		                         g_base_info_get_name (signal_info),
-		                         n_args, callback_type->getNumArgs ());
-		Debug::emit_error (error, compiler, expr->getLocStart ())
+		Debug::emit_error ("Incorrect number of arguments in signal "
+		                   "handler for signal ‘%0::%1’. Expected %2 "
+		                   "but saw %3.",
+		                   compiler, expr->getLocStart ())
+		<< gir_manager.get_c_name_for_type (static_gobject_info)
+		<< g_base_info_get_name (signal_info)
+		<< n_args
+		<< callback_type->getNumArgs ()
 		<< decl_range;
 
-		g_free (error);
-
 		return false;
 	}
 
@@ -578,25 +570,21 @@ _check_signal_callback_type (const Expr *expr,
 
 			if (actual_type_info == NULL) {
 				/* Error. */
-				gchar *error;
 
 				/* TODO: Emit expected type of signal callback? */
-				error = g_strdup_printf ("Failed to resolve "
-				                         "type of argument "
-				                         "‘%s’ in signal "
-				                         "handler for signal "
-				                         "‘%s::%s’. Cannot "
-				                         "find type with name "
-				                         "‘%s’.",
-				                         arg_name, c_type.c_str (),
-				                         g_base_info_get_name (signal_info),
-				                         actual_type_str.c_str ());
-				Debug::emit_warning (error, compiler,
+				Debug::emit_warning ("Failed to resolve type "
+				                     "of argument ‘%0’ in "
+				                     "signal handler for "
+				                     "signal ‘%1::%2’. Cannot "
+				                     "find type with name "
+				                     "‘%3’.", compiler,
 				                     expr->getLocStart ())
+				<< arg_name
+				<< c_type
+				<< g_base_info_get_name (signal_info)
+				<< actual_type_str
 				<< decl_range;
 
-				g_free (error);
-
 				continue;
 			}
 
@@ -652,26 +640,21 @@ _check_signal_callback_type (const Expr *expr,
 
 			if (expected_type.isNull ()) {
 				/* Error. */
-				gchar *error;
 
 				/* TODO: Emit expected type of signal callback? */
-				std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-				error = g_strdup_printf ("Failed to resolve "
-				                         "type of argument "
-				                         "‘%s’ in signal "
-				                         "handler for signal "
-				                         "‘%s::%s’. Cannot "
-				                         "find type with name "
-				                         "‘%s’.",
-				                         arg_name, c_type.c_str (),
-				                         g_base_info_get_name (signal_info),
-				                         g_base_info_get_name (&expected_type_info));
-				Debug::emit_warning (error, compiler,
+				Debug::emit_warning ("Failed to resolve type "
+				                     "of argument ‘%0’ in "
+				                     "signal handler for "
+				                     "signal ‘%1::%2’. Cannot "
+				                     "find type with name "
+				                     "‘%3’.", compiler,
 				                     expr->getLocStart ())
+				<< arg_name
+				<< gir_manager.get_c_name_for_type (static_gobject_info)
+				<< g_base_info_get_name (signal_info)
+				<< g_base_info_get_name (&expected_type_info)
 				<< decl_range;
 
-				g_free (error);
-
 				continue;
 			}
 
@@ -690,24 +673,20 @@ _check_signal_callback_type (const Expr *expr,
 		 * so further errors would just be noise. */
 		if (type_error) {
 			/* Error. */
-			gchar *error;
 
 			/* TODO: Emit expected type of signal callback? */
-			std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-			error = g_strdup_printf ("Incorrect type for argument "
-			                         "‘%s’ in signal handler for "
-			                         "signal ‘%s::%s’. Expected "
-			                         "‘%s’ but saw ‘%s’.",
-			                         arg_name, c_type.c_str (),
-			                         g_base_info_get_name (signal_info),
-			                         expected_type.getAsString ().c_str (),
-			                         actual_type.getAsString ().c_str ());
-			Debug::emit_error (error, compiler,
+			Debug::emit_error ("Incorrect type for argument ‘%0’ "
+			                   "in signal handler for signal "
+			                   "‘%1::%2’. Expected ‘%3’ but saw "
+			                   "‘%4’.", compiler,
 			                   expr->getLocStart ())
+			<< arg_name
+			<< gir_manager.get_c_name_for_type (static_gobject_info)
+			<< g_base_info_get_name (signal_info)
+			<< expected_type.getAsString ()
+			<< actual_type.getAsString ()
 			<< decl_range;
 
-			g_free (error);
-
 			return false;
 		}
 	}
@@ -719,44 +698,33 @@ _check_signal_callback_type (const Expr *expr,
 	                                    gir_manager);
 	if (expected_type.isNull ()) {
 		/* Error. */
-		gchar *error;
 
 		/* TODO: Emit expected type of signal callback? */
-		std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-		error = g_strdup_printf ("Failed to resolve return type in "
-		                         "signal handler for signal ‘%s::%s’. "
-		                         "Cannot find type with name ‘%s’.",
-		                         c_type.c_str (),
-		                         g_base_info_get_name (signal_info),
-		                         g_base_info_get_name (&expected_type_info));
-		Debug::emit_warning (error, compiler,
+		Debug::emit_warning ("Failed to resolve return type in signal "
+		                     "handler for signal ‘%0::%1’. Cannot find "
+		                     "type with name ‘%2’.", compiler,
 		                     expr->getLocStart ())
+		<< gir_manager.get_c_name_for_type (static_gobject_info)
+		<< g_base_info_get_name (signal_info)
+		<< g_base_info_get_name (&expected_type_info)
 		<< decl_range;
 
-		g_free (error);
-
 		return false;
 	}
 
 	if (!context.hasSameType (actual_type, expected_type)) {
 		/* Error. */
-		gchar *error;
 
 		/* TODO: Emit expected type of signal callback? */
-		std::string c_type (gir_manager.get_c_name_for_type (static_gobject_info));
-		error = g_strdup_printf ("Incorrect return type from "
-		                         "signal handler for signal ‘%s::%s’. "
-		                         "Expected ‘%s’ but saw ‘%s’.",
-		                         c_type.c_str (),
-		                         g_base_info_get_name (signal_info),
-		                         expected_type.getAsString ().c_str (),
-		                         actual_type.getAsString ().c_str ());
-		Debug::emit_error (error, compiler,
-		                   expr->getLocStart ())
+		Debug::emit_error ("Incorrect return type from signal handler "
+		                   "for signal ‘%0::%1’. Expected ‘%2’ but saw "
+		                   "‘%3’.", compiler, expr->getLocStart ())
+		<< gir_manager.get_c_name_for_type (static_gobject_info)
+		<< g_base_info_get_name (signal_info)
+		<< expected_type.getAsString ()
+		<< actual_type.getAsString ()
 		<< decl_range;
 
-		g_free (error);
-
 		return false;
 	}
 
@@ -825,21 +793,16 @@ _check_gsignal_callback_type (const CallExpr &call,
 	                                              context, gir_manager);
 	if (dynamic_gobject_info == NULL) {
 		/* Warning. */
-		gchar *error;
-
-		error = g_strdup_printf ("Could not find GObject subclass for "
-		                         "expression when connecting to signal "
-		                         "‘%s’. To improve static analysis, "
-		                         "add a typecast to the GObject "
-		                         "parameter of %s().",
-		                         signal_name.c_str (),
-		                         func_info->func_name);
-		Debug::emit_warning (error, compiler, call.getLocStart ())
+		Debug::emit_warning ("Could not find GObject subclass for "
+		                     "expression when connecting to signal "
+		                     "‘%0’. To improve static analysis, add a "
+		                     "typecast to the GObject parameter of "
+		                     "%1().", compiler, call.getLocStart ())
+		<< signal_name
+		<< func_info->func_name
 		<< gobject_arg->getSourceRange ()
 		<< signal_name_arg->getSourceRange ();
 
-		g_free (error);
-
 		return false;
 	}
 
@@ -857,20 +820,16 @@ _check_gsignal_callback_type (const CallExpr &call,
 	                                       signal_name.c_str ());
 	if (signal_info == NULL) {
 		/* Warning. */
-		gchar *error;
-
-		std::string c_type (gir_manager.get_c_name_for_type (dynamic_gobject_info));
-		error = g_strdup_printf ("No signal named ‘%s’ in GObject "
-		                         "class ‘%s’. To improve static "
-		                         "analysis, add a typecast to the "
-		                         "GObject parameter of %s().",
-		                         signal_name.c_str (), c_type.c_str (),
-		                         func_info->func_name);
-		Debug::emit_warning (error, compiler, call.getLocStart ())
+		Debug::emit_warning ("No signal named ‘%0’ in GObject class "
+		                     "‘%1’. To improve static analysis, add a "
+		                     "typecast to the GObject parameter of "
+		                     "%2().", compiler, call.getLocStart ())
+		<< signal_name
+		<< gir_manager.get_c_name_for_type (dynamic_gobject_info)
+		<< func_info->func_name
 		<< gobject_arg->getSourceRange ()
 		<< signal_name_arg->getSourceRange ();
 
-		g_free (error);
 		g_base_info_unref (dynamic_gobject_info);
 
 		return false;
diff --git a/clang-plugin/gvariant-checker.cpp b/clang-plugin/gvariant-checker.cpp
index 03b653e..e32dddf 100644
--- a/clang-plugin/gvariant-checker.cpp
+++ b/clang-plugin/gvariant-checker.cpp
@@ -286,15 +286,10 @@ _consume_variadic_argument (QualType expected_type,
 	       expected_type.getAsString () << "’.");
 
 	if (*args_begin == *args_end) {
-		gchar *error;
-
-		error = g_strdup_printf (
-			"Expected a GVariant variadic argument of type ‘%s’ "
-			"but there wasn’t one.",
-			expected_type_str.c_str ());
-		Debug::emit_error (error, compiler,
-		                   format_arg_str->getLocStart ());
-		g_free (error);
+		Debug::emit_error ("Expected a GVariant variadic argument of "
+		                   "type ‘%0’ but there wasn’t one.", compiler,
+		                   format_arg_str->getLocStart ())
+		<< expected_type_str;
 
 		return false;
 	}
@@ -320,15 +315,10 @@ _consume_variadic_argument (QualType expected_type,
 
 	if (is_null_constant && !(flags & CHECK_FLAG_ALLOW_MAYBE) &&
 	    expected_type->isPointerType ()) {
-		gchar *error;
-
-		error = g_strdup_printf (
-			"Expected a GVariant variadic argument of type ‘%s’ "
-			"but saw NULL instead.",
-			expected_type_str.c_str ());
-		Debug::emit_error (error, compiler,
-		                   arg->getLocStart ());
-		g_free (error);
+		Debug::emit_error ("Expected a GVariant variadic argument of "
+		                   "type ‘%0’ but saw NULL instead.", compiler,
+		                   arg->getLocStart ())
+		<< expected_type_str;
 
 		return false;
 	} else if (!is_null_constant &&
@@ -342,16 +332,12 @@ _consume_variadic_argument (QualType expected_type,
 		 * hacky approach instead. */
 		const PointerType *actual_pointer_type = dyn_cast<PointerType> (actual_type);
 		if (actual_pointer_type == NULL) {
-			gchar *error;
-
-			error = g_strdup_printf (
-				"Expected a GVariant variadic argument of type "
-				"‘%s’ but saw one of type ‘%s’.",
-				expected_type_str.c_str (),
-				actual_type.getAsString ().c_str ());
-			Debug::emit_error (error, compiler,
-			                   arg->getLocStart ());
-			g_free (error);
+			Debug::emit_error ("Expected a GVariant variadic "
+			                   "argument of type ‘%0’ but saw one "
+			                   "of type ‘%1’.", compiler,
+			                   arg->getLocStart ())
+			<< expected_type_str
+			<< actual_type;
 
 			return false;
 		}
@@ -366,17 +352,13 @@ _consume_variadic_argument (QualType expected_type,
 		} else if (!(flags & CHECK_FLAG_FORCE_VALIST)) {
 			const PointerType *actual_pointer2_type = dyn_cast<PointerType> (actual_pointee_type);
 			if (actual_pointer2_type == NULL) {
-				gchar *error;
-
-				error = g_strdup_printf (
-					"Expected a GVariant variadic argument "
-					"of type ‘%s’ but saw one of type "
-					"‘%s’.",
-					expected_type_str.c_str (),
-					actual_type.getAsString ().c_str ());
-				Debug::emit_error (error, compiler,
-				                   arg->getLocStart ());
-				g_free (error);
+				Debug::emit_error ("Expected a GVariant "
+				                   "variadic argument of type "
+				                   "‘%0’ but saw one of type "
+				                   "‘%1’.", compiler,
+				                   arg->getLocStart ())
+				<< expected_type_str
+				<< actual_type;
 
 				return false;
 			}
@@ -394,16 +376,12 @@ _consume_variadic_argument (QualType expected_type,
 		      actual_pointee_type_str == "va_list") &&
 		     !(flags & CHECK_FLAG_FORCE_GVARIANTITER &&
 		      actual_pointee_type_str == "GVariantIter")) {
-			gchar *error;
-
-			error = g_strdup_printf (
-				"Expected a GVariant variadic argument of type "
-				"‘%s’ but saw one of type ‘%s’.",
-				expected_type_str.c_str (),
-				actual_type.getAsString ().c_str ());
-			Debug::emit_error (error, compiler,
-			                   arg->getLocStart ());
-			g_free (error);
+			Debug::emit_error ("Expected a GVariant variadic "
+			                   "argument of type ‘%0’ but saw one "
+			                   "of type ‘%1’.", compiler,
+			                   arg->getLocStart ())
+			<< expected_type_str
+			<< actual_type;
 
 			return false;
 		}
@@ -415,16 +393,12 @@ _consume_variadic_argument (QualType expected_type,
 		/* Normal non-GVariant, non-GVariantBuilder case. */
 		if (!_compare_types (actual_type, expected_type,
 		                     flags, context)) {
-			gchar *error;
-
-			error = g_strdup_printf (
-				"Expected a GVariant variadic argument of type "
-				"‘%s’ but saw one of type ‘%s’.",
-				expected_type.getAsString ().c_str (),
-				actual_type.getAsString ().c_str ());
-			Debug::emit_error (error, compiler,
-			                   arg->getLocStart ());
-			g_free (error);
+			Debug::emit_error ("Expected a GVariant variadic "
+			                   "argument of type ‘%0’ but saw one "
+			                   "of type ‘%1’.", compiler,
+			                   arg->getLocStart ())
+			<< expected_type
+			<< actual_type;
 
 			return false;
 		}
@@ -504,13 +478,10 @@ _check_basic_type_string (const gchar **type_str,
 		flags |= CHECK_FLAG_FORCE_GVARIANT;
 		break;
 	default:
-		gchar *error;
-
-		error = g_strdup_printf ("Expected a GVariant basic type "
-		                         "string but saw ‘%c’.", **type_str);
-		Debug::emit_error (error, compiler,
-		                   format_arg_str->getLocStart ());
-		g_free (error);
+		Debug::emit_error ("Expected a GVariant basic type string but "
+		                   "saw ‘%0’.", compiler,
+		                   format_arg_str->getLocStart ())
+		<< **type_str;
 
 		return false;
 	}
@@ -620,11 +591,10 @@ _check_type_string (const gchar **type_str,
 		}
 
 		if (**type_str != ')') {
-			Debug::emit_error (
-				"Invalid GVariant type string: tuple "
-				"did not end with ‘)’.",
-				compiler,
-				format_arg_str->getLocStart ());
+			Debug::emit_error ("Invalid GVariant type string: "
+			                   "tuple did not end with ‘)’.",
+			                   compiler,
+			                   format_arg_str->getLocStart ());
 			return false;
 		}
 
@@ -985,12 +955,12 @@ _check_gvariant_format_param (const CallExpr& call,
 	const StringLiteral *format_arg_str = dyn_cast<StringLiteral> (format_arg);
 	if (format_arg_str == NULL) {
 		Debug::emit_warning (
-			"Non-literal GVariant format string in call to " +
-			func.getNameAsString () +
-			"(). Cannot check format string correctness. Instead "
+			"Non-literal GVariant format string in call to %0(). "
+			"Cannot check format string correctness. Instead "
 			"of a non-literal format string, use GVariantBuilder.",
 			compiler,
-			format_arg->getLocStart ());
+			format_arg->getLocStart ())
+		<< func.getNameAsString ();
 		return false;
 	}
 
@@ -1034,17 +1004,13 @@ _check_gvariant_format_param (const CallExpr& call,
 	 * string. Don’t emit any error messages about unpaired variadic
 	 * arguments because that would just confuse things. */
 	if (*format_str != '\0') {
-		gchar *error;
-
-		error = g_strdup_printf ("Unexpected GVariant format strings "
-		                         "‘%s’ with unpaired arguments. If "
-		                         "using multiple format strings, they "
-		                         "should be enclosed in brackets to "
-		                         "create a tuple (e.g. ‘(%s)’).",
-		                         format_str, whole_format_str);
-		Debug::emit_error (error, compiler,
-		                   format_arg_str->getLocStart ());
-		g_free (error);
+		Debug::emit_error ("Unexpected GVariant format strings ‘%0’ "
+		                   "with unpaired arguments. If using multiple "
+		                   "format strings, they should be enclosed in "
+		                   "brackets to create a tuple (e.g. ‘(%1)’).",
+		                   compiler, format_arg_str->getLocStart ())
+		<< format_str
+		<< whole_format_str;
 
 		g_free (whole_format_str);
 
@@ -1059,33 +1025,33 @@ _check_gvariant_format_param (const CallExpr& call,
 	for (; !func_info->uses_va_list && args_begin != args_end;
 	     ++args_begin) {
 		const Expr *arg = *args_begin;
-		gchar *error;
 		gchar *error_format_str;
 
 		error_format_str = _gvariant_format_string_for_type (arg->getType ());
 
 		if (error_format_str != NULL) {
-			error = g_strdup_printf (
-				"Unexpected GVariant variadic argument of type "
-				"‘%s’. A ‘%s’ GVariant format string should be "
-				"added to the format argument to use it.",
-				arg->getType ().getAsString ().c_str (),
-				error_format_str);
+			Debug::emit_error ("Unexpected GVariant variadic "
+			                   "argument of type ‘%0’. A ‘%1’ "
+			                   "GVariant format string should be "
+			                   "added to the format argument to "
+			                   "use it.",
+			                   compiler, arg->getLocStart ())
+			<< arg->getType ()
+			<< error_format_str;
 		} else {
-			error = g_strdup_printf (
-				"Unexpected GVariant variadic argument of type "
-				"‘%s’. A GVariant format string should be "
-				"added to the format argument to use it, but "
-				"there is no known GVariant representation of "
-				"the argument’s type. The argument must be "
-				"serialized to a GVariant-representable type "
-				"first.",
-				arg->getType ().getAsString ().c_str ());
+			Debug::emit_error ("Unexpected GVariant variadic "
+			                   "argument of type ‘%0’. A GVariant "
+			                   "format string should be added to "
+			                   "the format argument to use it, but "
+			                   "there is no known GVariant "
+			                   "representation of the argument’s "
+			                   "type. The argument must be "
+			                   "serialized to a "
+			                   "GVariant-representable type first.",
+			                   compiler, arg->getLocStart ())
+			<< arg->getType ();
 		}
 
-		Debug::emit_error (error, compiler, arg->getLocStart ());
-		g_free (error);
-
 		retval = false;
 	}
 
diff --git a/clang-plugin/nullability-checker.cpp b/clang-plugin/nullability-checker.cpp
index 3ad564b..475d244 100644
--- a/clang-plugin/nullability-checker.cpp
+++ b/clang-plugin/nullability-checker.cpp
@@ -218,80 +218,77 @@ NullabilityVisitor::TraverseFunctionDecl (FunctionDecl* func)
 		if (has_nonnull == EXPLICIT_NONNULL && has_allow_none) {
 			Debug::emit_error (
 				"Conflict between nonnull attribute and "
-				"(allow-none) annotation on the ‘" +
-				parm_decl->getNameAsString () +
-				"’ parameter of function " +
-				func->getNameAsString () + "().",
+				"(allow-none) annotation on the ‘%0’ parameter "
+				"of function %1().",
 				this->_compiler,
-				parm_decl->getLocStart ());
+				parm_decl->getLocStart ())
+			<< parm_decl->getNameAsString ()
+			<< func->getNameAsString ();
 		} else if (has_allow_none && has_assertion) {
 			Debug::emit_error (
 				"Conflict between (allow-none) annotation and "
-				"non-NULL precondition assertion on the ‘" +
-				parm_decl->getNameAsString () +
-				"’ parameter of function " +
-				func->getNameAsString () + "().",
+				"non-NULL precondition assertion on the ‘%0’ "
+				"parameter of function %1().",
 				this->_compiler,
-				parm_decl->getLocStart ());
+				parm_decl->getLocStart ())
+			<< parm_decl->getNameAsString ()
+			<< func->getNameAsString ();
 		} else if (!has_allow_none && !has_assertion) {
 			switch (has_nonnull) {
 			case EXPLICIT_NULLABLE:
 				Debug::emit_warning (
 					"Missing (allow-none) annotation on "
-					"the ‘" +
-					parm_decl->getNameAsString () +
-					"’ parameter of function " +
-					func->getNameAsString () + "() "
+					"the ‘%0’ parameter of function %1() "
 					"(already has a nonnull attribute or "
 					"no non-NULL precondition assertion).",
 					this->_compiler,
-					parm_decl->getLocStart ());
+					parm_decl->getLocStart ())
+				<< parm_decl->getNameAsString ()
+				<< func->getNameAsString ();
 				break;
 			case MAYBE:
 				Debug::emit_warning (
 					"Missing (allow-none) annotation or "
 					"non-NULL precondition assertion on "
-					"the ‘" +
-					parm_decl->getNameAsString () +
-					"’ parameter of function " +
-					func->getNameAsString () + "().",
+					"the ‘%0’ parameter of function %1().",
 					this->_compiler,
-					parm_decl->getLocStart ());
+					parm_decl->getLocStart ())
+				<< parm_decl->getNameAsString ()
+				<< func->getNameAsString ();
 				break;
 			case EXPLICIT_NONNULL:
 				Debug::emit_warning (
 					"Missing non-NULL precondition "
-					"assertion on the ‘" +
-					parm_decl->getNameAsString () +
-					"’ parameter of function " +
-					func->getNameAsString () + "() "
-					"(already has a nonnull attribute or "
-					"no (allow-none) annotation).",
+					"assertion on the ‘%0’ parameter of "
+					"function %1() (already has a nonnull "
+					"attribute or no (allow-none) "
+					"annotation).",
 					this->_compiler,
-					parm_decl->getLocStart ());
+					parm_decl->getLocStart ())
+				<< parm_decl->getNameAsString ()
+				<< func->getNameAsString ();
 				break;
 			}
 		} else if (has_nonnull == EXPLICIT_NULLABLE && has_assertion) {
 			Debug::emit_warning (
 				"Conflict between nonnull attribute and "
-				"non-NULL precondition annotation on the ‘" +
-				parm_decl->getNameAsString () +
-				"’ parameter of function " +
-				func->getNameAsString () + "().",
+				"non-NULL precondition annotation on the ‘%0’ "
+				"parameter of function %1().",
 				this->_compiler,
-				parm_decl->getLocStart ());
+				parm_decl->getLocStart ())
+			<< parm_decl->getNameAsString ()
+			<< func->getNameAsString ();
 		} else if (has_nonnull == MAYBE && has_assertion) {
 			/* TODO: Make this a soft warning (disabled by default)
 			 * if it comes up with too many false positives. */
 			Debug::emit_warning (
-				"Missing nonnull attribute for the ‘" +
-				parm_decl->getNameAsString () +
-				"’ parameter of function " +
-				func->getNameAsString () + "() "
-				"(already has a non-NULL precondition "
-				"assertion).",
+				"Missing nonnull attribute for the ‘%0’ "
+				"parameter of function %1() (already has a "
+				"non-NULL precondition assertion).",
 				this->_compiler,
-				parm_decl->getLocStart ());
+				parm_decl->getLocStart ())
+			<< parm_decl->getNameAsString ()
+			<< func->getNameAsString ();
 		}
 	}
 
diff --git a/clang-plugin/plugin.cpp b/clang-plugin/plugin.cpp
index de5f6bf..22c423b 100644
--- a/clang-plugin/plugin.cpp
+++ b/clang-plugin/plugin.cpp
@@ -140,18 +140,14 @@ private:
 			if (error != NULL) {
 				/* Warn about the bogus include path and
 				 * continue. */
-				gchar *error_msg;
 				DiagnosticsEngine &d = CI.getDiagnostics ();
 
-				error_msg = g_strdup_printf (
-					"Error opening typelib path ‘%s’: %s",
-					typelib_path, error->message);
-
 				unsigned int id = d.getCustomDiagID (
-					DiagnosticsEngine::Warning, error_msg);
-				d.Report (id);
-
-				g_free (error_msg);
+					DiagnosticsEngine::Warning,
+					"Error opening typelib path ‘%0’: %1");
+				d.Report (id)
+					<< typelib_path
+					<< error->message;
 
 				continue;
 			}