Macro

Debug macro

gcc -E

https://stackoverflow.com/a/4575001

stackoverflow What are the useful GCC flags for C? # A

-save-temps

This leaves behind the results of the preprocessor and the assembly.

The preprocessed source is useful for debugging macros.

The assembly is useful for determining what optimizations went into effect. For instance, you may want to verify that GCC is doing tail call optimization on some recursive functions, as without it you can potentially overflow the stack.

What are the useful GCC flags for C? #

Trick

本节讨论在定义macro的时候的一些技巧

do{}while(0) in macro

https://stackoverflow.com/questions/154136/why-use-apparently-meaningless-do-while-and-if-else-statements-in-macros

https://stackoverflow.com/questions/257418/do-while-0-what-is-it-good-for

https://stackoverflow.com/questions/154136/why-use-apparently-meaningless-do-while-and-if-else-statements-in-macros

https://stackoverflow.com/questions/1067226/c-multi-line-macro-do-while0-vs-scope-block

Useful macro

fluentcpp 3 Types of Macros That Improve C++ Code

Useful macro #1: The macro that bridges a gap between two C++ features

#define DEFINE_VISITABLE() \
   virtual ReturnType Accept(BaseVisitor& guest) \
   { return AcceptImpl(*this, guest); }

Useful macro #2: The macro that shortens a redundant expression

FWD

来源：Vittorio Romeo’s FWD macro

template<typename MyType, typename MyOtherType>
void f(MyType&& myValue, MyOtherType&& myOtherValue)
{
    g(std::forward<MyType>(myValue), std::forward<MyOtherType>(myOtherValue));
}

Vittorio proposes to use the following macro:

#define FWD(...) ::std::forward<decltype(__VA_ARGS__)>(__VA_ARGS__)

Here is how the previous code now looks like by using it:

template<typename MyType, typename MyOtherType>
void f(MyType&& myValue, MyOtherType&& myOtherValue)
{
    g(FWD(myValue), FWD(myOtherValue));
}

noexcept(noexcept(

来源：item 14 of Effective Modern C++

macro function

https://stackoverflow.com/questions/163365/how-do-i-make-a-c-macro-behave-like-a-function

C++ Use macros to define class member of a single class

Can I comment multi-line macros?

Use macro to define function

对于template class，如果将function definition放到单独的文件，则需要使用如下语法

template<typename T1, typename T2...>
void C<T1, T2...>::Function()
{

}

如果有多个template parameter，则写起来就非常不便利，那么如何来缓解这个问题呢？使用c++ macro来进行实现：

/**
 * 模板声明的宏
 */
#define TEMPLATE_DECLARATION template <typename T1, typename T2, typename T3, ...>

/**
 * 模板参数声明
 */
#define TEMPLATE_PARAMETER_DECLARATION T1, T2, T3 ...

/**
 * 定义成员方法的宏
 */
#define DEFINE_METHOD(RETURN, METHOD) \
    TEMPLATE_DECLARATION              \
    RETURN ClassName<TEMPLATE_PARAMETER_DECLARATION>::METHOD

下面是一个简单的例子：

#define DEFINE_METHOD(METHOD) template<typename T>\
C<T>::METHOD \

template<typename T>
class C
{
public:
    C();
    T m_t;
};
DEFINE_METHOD(C())
{m_t = 0;
}

int main()
{

}