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| -rw-r--r-- | base/macros.h | 56 |
1 files changed, 0 insertions, 56 deletions
diff --git a/base/macros.h b/base/macros.h index 7817515..2741afc 100644 --- a/base/macros.h +++ b/base/macros.h @@ -153,64 +153,8 @@ inline To implicit_cast(From const &f) { // 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 { -}; - -#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 - // bit_cast<Dest,Source> is a template function that implements the // equivalent of "*reinterpret_cast<Dest*>(&source)". We need this in // very low-level functions like the protobuf library and fast math |