Visual-C ++和gcc之间的宏##连接运算符的差异 [英] Differences in Macro ## concatenation operator between Visual-C++ and gcc

问题描述

  #define STRUCTMEMBER（（））（）成员，价值）GlobalStructInstance。 ## Member =价值
 ... 
 STRUCTMEMBER（Item，1）; 
  

这在Visual C ++中完美工作，但gcc 3.4.5（MingGW）产生以下错误： / p>

粘贴。和Item不会给出有效的预处理令牌

当我使用 - >运算符时，也会发生这种情况。我没有发现关于连接的提示，这些操作符的使用是被禁止的。

有人有想法吗？

解决方案

也许Visual C ++将两个空格粘贴在一起以创建另一个空间。不是空格是代币，但它可以让你的代码工作。

object.member 不是一个令牌，它是三个令牌，所以你不需要使用令牌粘贴来实现你描述的宏。只需删除'##'，它就可以在任何地方工作。

I'm having a macro like this ( not exactly, but function is quite equivalent):

#define STRUCTMEMBER(Member,Value) GlobalStructInstance. ## Member = Value
...
STRUCTMEMBER(Item,1);

This works perfectly in Visual C++, but gcc 3.4.5 (MingGW) yield the following error:

pasting "." and "Item" does not give a valid preprocessing token

This also happens when I use the "->" operator. I didn't found hints on concatenation, that the usage of these operators is forbidden.

Does anyone have an idea ?

解决方案

Maybe Visual C++ is pasting a couple of spaces together to make another space. Not that whitespaces are tokens, but it would allow your code to work.

object.member is not a token, it's three tokens, so you don't need token-pasting to implement the macro you describe. Just remove the '##' and it should work everywhere.

[Edit: just checked, and the result of using ## to form something that isn't a valid token is undefined. So GCC is allowed to reject it and MSVC is allowed to ignore it and perform no paste, as far as I can tell.]

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