Revert removing of compile_assert.h.
In https://webrtc-codereview.appspot.com/39469004 compile_assert.h is removed and that resulted in some bots to break. There is a pending CL to fix the issue https://chromereviews.googleplex.com/141837013/
, meanwhile I revert this change.
TBR=kwiberg@google.com
Review URL: https://webrtc-codereview.appspot.com/35779004
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8064 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/webrtc/base/compile_assert.h b/webrtc/base/compile_assert.h
new file mode 100644
index 0000000..47d40a9
--- /dev/null
+++ b/webrtc/base/compile_assert.h
@@ -0,0 +1,90 @@
+/*
+ * Copyright 2013 The WebRTC Project Authors. All rights reserved.
+ *
+ * Use of this source code is governed by a BSD-style license
+ * that can be found in the LICENSE file in the root of the source
+ * tree. An additional intellectual property rights grant can be found
+ * in the file PATENTS. All contributing project authors may
+ * be found in the AUTHORS file in the root of the source tree.
+ */
+
+// Borrowed from Chromium's src/base/macros.h.
+
+#ifndef WEBRTC_BASE_COMPILE_ASSERT_H_
+#define WEBRTC_BASE_COMPILE_ASSERT_H_
+
+// The COMPILE_ASSERT macro can be used to verify that a compile time
+// expression is true. For example, you could use it to verify the
+// size of a static array:
+//
+// COMPILE_ASSERT(ARRAYSIZE_UNSAFE(content_type_names) == CONTENT_NUM_TYPES,
+// content_type_names_incorrect_size);
+//
+// or to make sure a struct is smaller than a certain size:
+//
+// COMPILE_ASSERT(sizeof(foo) < 128, foo_too_large);
+//
+// The second argument to the macro is the name of the variable. If
+// the expression is false, most compilers will issue a warning/error
+// containing the name of the variable.
+
+// TODO(ajm): Hack to avoid multiple definitions until the base/ of webrtc and
+// libjingle are merged.
+#if !defined(COMPILE_ASSERT)
+#if __cplusplus >= 201103L
+// Under C++11, just use static_assert.
+#define COMPILE_ASSERT(expr, msg) static_assert(expr, #msg)
+
+#else
+template <bool>
+struct CompileAssert {
+};
+
+#define COMPILE_ASSERT(expr, msg) \
+ typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1]
+
+#endif // __cplusplus >= 201103L
+#endif // !defined(COMPILE_ASSERT)
+
+// Implementation details of COMPILE_ASSERT:
+//
+// - COMPILE_ASSERT works by defining an array type that has -1
+// elements (and thus is invalid) when the expression is false.
+//
+// - The simpler definition
+//
+// #define COMPILE_ASSERT(expr, msg) typedef char msg[(expr) ? 1 : -1]
+//
+// does not work, as gcc supports variable-length arrays whose sizes
+// are determined at run-time (this is gcc's extension and not part
+// of the C++ standard). As a result, gcc fails to reject the
+// following code with the simple definition:
+//
+// int foo;
+// COMPILE_ASSERT(foo, msg); // not supposed to compile as foo is
+// // not a compile-time constant.
+//
+// - By using the type CompileAssert<(bool(expr))>, we ensures that
+// expr is a compile-time constant. (Template arguments must be
+// determined at compile-time.)
+//
+// - The outer parentheses in CompileAssert<(bool(expr))> are necessary
+// to work around a bug in gcc 3.4.4 and 4.0.1. If we had written
+//
+// CompileAssert<bool(expr)>
+//
+// instead, these compilers will refuse to compile
+//
+// COMPILE_ASSERT(5 > 0, some_message);
+//
+// (They seem to think the ">" in "5 > 0" marks the end of the
+// template argument list.)
+//
+// - The array size is (bool(expr) ? 1 : -1), instead of simply
+//
+// ((expr) ? 1 : -1).
+//
+// This is to avoid running into a bug in MS VC 7.1, which
+// causes ((0.0) ? 1 : -1) to incorrectly evaluate to 1.
+
+#endif // WEBRTC_BASE_COMPILE_ASSERT_H_
