c++ - 在 C++ 中使用宏生成函数

Question

我有以下旨在在当前作用域或命名空间中生成函数的宏:

#define MAKE_FUNC(FNAME) \
template <typename T> \
T ##FNAME## (const T& t) \
{\
   return t; \
}

MAKE_FUNC(foo)
MAKE_FUNC(boo)

int main()
{
   foo(1);
   boo(2);
}

以下是编译上述代码时的错误信息:

prog.cpp:8:1: error: pasting "Tfoo" and "(" does not give a valid preprocessing token
prog.cpp:9:1: error: pasting "Tboo" and "(" does not give a valid preprocessing token
prog.cpp:8: error: ISO C++ forbids declaration of ‘Tfoo’ with no type
prog.cpp:9: error: ISO C++ forbids declaration of ‘Tboo’ with no type
prog.cpp: In function ‘int main()’:
prog.cpp:13: error: ‘foo’ was not declared in this scope
prog.cpp:14: error: ‘boo’ was not declared in this scope

http://ideone.com/paiu1

好像连接失败了，请问有没有这个问题？

Answer 1

你想要

T FNAME (const T& t) \

## 拼接，你不想拼接。