| /* |
| * libjingle |
| * Copyright 2013, Google Inc. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions are met: |
| * |
| * 1. Redistributions of source code must retain the above copyright notice, |
| * this list of conditions and the following disclaimer. |
| * 2. Redistributions in binary form must reproduce the above copyright notice, |
| * this list of conditions and the following disclaimer in the documentation |
| * and/or other materials provided with the distribution. |
| * 3. The name of the author may not be used to endorse or promote products |
| * derived from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR IMPLIED |
| * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF |
| * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO |
| * EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, |
| * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, |
| * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; |
| * OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, |
| * WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR |
| * OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF |
| * ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. |
| */ |
| |
| // COMPILE_ASSERT macro, borrowed from google3/base/macros.h. |
| #ifndef TALK_BASE_COMPILE_ASSERT_H_ |
| #define TALK_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(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) |
| template <bool> |
| struct CompileAssert { |
| }; |
| |
| #define COMPILE_ASSERT(expr, msg) \ |
| typedef CompileAssert<(bool(expr))> msg[bool(expr) ? 1 : -1] // NOLINT |
| #endif // 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 // TALK_BASE_COMPILE_ASSERT_H_ |