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Diffstat (limited to 'include/gtest/internal/gtest-port.h')
| -rw-r--r-- | include/gtest/internal/gtest-port.h | 137 |
1 files changed, 137 insertions, 0 deletions
diff --git a/include/gtest/internal/gtest-port.h b/include/gtest/internal/gtest-port.h index a2a62be9..f2c80f34 100644 --- a/include/gtest/internal/gtest-port.h +++ b/include/gtest/internal/gtest-port.h @@ -609,6 +609,91 @@ namespace internal { class String; +// The GTEST_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: +// +// GTEST_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: +// +// GTEST_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. + +template <bool> +struct CompileAssert { +}; + +#define GTEST_COMPILE_ASSERT_(expr, msg) \ + typedef ::testing::internal::CompileAssert<(bool(expr))> \ + msg[bool(expr) ? 1 : -1] + +// Implementation details of GTEST_COMPILE_ASSERT_: +// +// - GTEST_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 GTEST_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; +// GTEST_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 outter 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 +// +// GTEST_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. + +// StaticAssertTypeEqHelper is used by StaticAssertTypeEq defined in gtest.h. +// +// This template is declared, but intentionally undefined. +template <typename T1, typename T2> +struct StaticAssertTypeEqHelper; + +template <typename T> +struct StaticAssertTypeEqHelper<T, T> {}; + +#if GTEST_HAS_GLOBAL_STRING +typedef ::string string; +#else +typedef ::std::string string; +#endif // GTEST_HAS_GLOBAL_STRING + +#if GTEST_HAS_GLOBAL_WSTRING +typedef ::wstring wstring; +#elif GTEST_HAS_STD_WSTRING +typedef ::std::wstring wstring; +#endif // GTEST_HAS_GLOBAL_WSTRING + typedef ::std::stringstream StrStream; // A helper for suppressing warnings on constant condition. It just @@ -790,6 +875,58 @@ inline void FlushInfoLog() { fflush(NULL); } // INTERNAL IMPLEMENTATION - DO NOT USE IN USER CODE. // +// Use implicit_cast as a safe version of static_cast for upcasting in +// the type hierarchy (e.g. casting a Foo* to a SuperclassOfFoo* or a +// const Foo*). When you use implicit_cast, the compiler checks that +// the cast is safe. Such explicit implicit_casts are necessary in +// surprisingly many situations where C++ demands an exact type match +// instead of an argument type convertable to a target type. +// +// The syntax for using implicit_cast is the same as for static_cast: +// +// implicit_cast<ToType>(expr) +// +// implicit_cast would have been part of the C++ standard library, +// but the proposal was submitted too late. It will probably make +// its way into the language in the future. +template<typename To> +inline To implicit_cast(To x) { return x; } + +// When you upcast (that is, cast a pointer from type Foo to type +// SuperclassOfFoo), it's fine to use implicit_cast<>, since upcasts +// always succeed. When you downcast (that is, cast a pointer from +// type Foo to type SubclassOfFoo), static_cast<> isn't safe, because +// how do you know the pointer is really of type SubclassOfFoo? It +// could be a bare Foo, or of type DifferentSubclassOfFoo. Thus, +// when you downcast, you should use this macro. In debug mode, we +// use dynamic_cast<> to double-check the downcast is legal (we die +// if it's not). In normal mode, we do the efficient static_cast<> +// instead. Thus, it's important to test in debug mode to make sure +// the cast is legal! +// This is the only place in the code we should use dynamic_cast<>. +// In particular, you SHOULDN'T be using dynamic_cast<> in order to +// do RTTI (eg code like this: +// if (dynamic_cast<Subclass1>(foo)) HandleASubclass1Object(foo); +// if (dynamic_cast<Subclass2>(foo)) HandleASubclass2Object(foo); +// You should design the code some other way not to need this. +template<typename To, typename From> // use like this: down_cast<T*>(foo); +inline To down_cast(From* f) { // so we only accept pointers + // Ensures that To is a sub-type of From *. This test is here only + // for compile-time type checking, and has no overhead in an + // optimized build at run-time, as it will be optimized away + // completely. + if (false) { + const To to = NULL; + ::testing::internal::implicit_cast<From*>(to); + } + +#if GTEST_HAS_RTTI + // RTTI: debug mode only! + GTEST_CHECK_(f == NULL || dynamic_cast<To>(f) != NULL); +#endif + return static_cast<To>(f); +} + // Downcasts the pointer of type Base to Derived. // Derived must be a subclass of Base. The parameter MUST // point to a class of type Derived, not any subclass of it. |