Use static_assert unconditionally.chromium/2190chromium/2189

BUG=none
TEST=none
R=jam@chromium.org

Review URL: https://codereview.chromium.org/605273004

1 files changed, 31 insertions, 98 deletions

diff --git a/third_party/macros.h b/third_party/macros.h
index 84c4366b16..92d4f34bda 100644
--- a/third_party/macros.h
+++ b/third_party/macros.h
@@ -1,98 +1,31 @@
-// Copyright 2014 The Chromium Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style license that can be
-// found in the LICENSE file.
-
-// This file contains macros and macro-like constructs (e.g., templates) that
-// are commonly used throughout Chromium source. (It may also contain things
-// that are closely related to things that are commonly used that belong in this
-// file.)
-
-#ifndef BASE_MACROS_H_
-#define BASE_MACROS_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.
-
-#undef 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 {
-};
-
-// Annotate a variable indicating it's ok if the variable is not used.
-// (Typically used to silence a compiler warning when the assignment
-// is important for some other reason.)
-// Use like:
-//   int x ALLOW_UNUSED = ...;
-#if defined(COMPILER_GCC)
-#define ALLOW_UNUSED __attribute__((unused))
-#else
-#define ALLOW_UNUSED
-#endif
-
-#define COMPILE_ASSERT(expr, msg) \
-  typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] ALLOW_UNUSED
-
-// 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
-
-#endif  // BASE_MACROS_H_
+// Copyright 2014 The Chromium Authors. All rights reserved.

+// Use of this source code is governed by a BSD-style license that can be

+// found in the LICENSE file.

+

+// This file contains macros and macro-like constructs (e.g., templates) that

+// are commonly used throughout Chromium source. (It may also contain things

+// that are closely related to things that are commonly used that belong in this

+// file.)

+

+#ifndef BASE_MACROS_H_

+#define BASE_MACROS_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.

+

+#undef COMPILE_ASSERT

+#define COMPILE_ASSERT(expr, msg) static_assert(expr, #msg)

+

+#endif  // BASE_MACROS_H_