add support for -d explain to help debug why rules are running

1 files changed, 22 insertions, 0 deletions

diff --git a/src/explain.h b/src/explain.h
new file mode 100644
index 0000000..021f0d4
--- /dev/null
+++ b/src/explain.h
@@ -0,0 +1,22 @@
+// Copyright 2012 Google Inc. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <stdio.h>
+
+#define EXPLAIN(fmt, ...) {                                             \
+  if (g_explaining)                                                     \
+    fprintf(stderr, "ninja explain: " fmt "\n", __VA_ARGS__);           \
+}
+
+extern bool g_explaining;