1 files changed, 53 insertions, 0 deletions
diff --git a/include/private/SkMacros.h b/include/private/SkMacros.h
new file mode 100644
index 0000000000..3d79d52230
--- /dev/null
+++ b/include/private/SkMacros.h
@@ -0,0 +1,53 @@
+/*
+ * Copyright 2018 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+#ifndef SkMacros_DEFINED
+#define SkMacros_DEFINED
+
+/*
+ *  Usage:  SK_MACRO_CONCAT(a, b)   to construct the symbol ab
+ *
+ *  SK_MACRO_CONCAT_IMPL_PRIV just exists to make this work. Do not use directly
+ *
+ */
+#define SK_MACRO_CONCAT(X, Y)           SK_MACRO_CONCAT_IMPL_PRIV(X, Y)
+#define SK_MACRO_CONCAT_IMPL_PRIV(X, Y)  X ## Y
+
+/*
+ *  Usage: SK_MACRO_APPEND_LINE(foo)    to make foo123, where 123 is the current
+ *                                      line number. Easy way to construct
+ *                                      unique names for local functions or
+ *                                      variables.
+ */
+#define SK_MACRO_APPEND_LINE(name)  SK_MACRO_CONCAT(name, __LINE__)
+
+/**
+ * For some classes, it's almost always an error to instantiate one without a name, e.g.
+ *   {
+ *       SkAutoMutexAcquire(&mutex);
+ *       <some code>
+ *   }
+ * In this case, the writer meant to hold mutex while the rest of the code in the block runs,
+ * but instead the mutex is acquired and then immediately released.  The correct usage is
+ *   {
+ *       SkAutoMutexAcquire lock(&mutex);
+ *       <some code>
+ *   }
+ *
+ * To prevent callers from instantiating your class without a name, use SK_REQUIRE_LOCAL_VAR
+ * like this:
+ *   class classname {
+ *       <your class>
+ *   };
+ *   #define classname(...) SK_REQUIRE_LOCAL_VAR(classname)
+ *
+ * This won't work with templates, and you must inline the class' constructors and destructors.
+ * Take a look at SkAutoFree and SkAutoMalloc in this file for examples.
+ */
+#define SK_REQUIRE_LOCAL_VAR(classname) \
+    static_assert(false, "missing name for " #classname)
+
+#endif  // SkMacros_DEFINED