将需要逗号的模板传递给单参数宏 [英] Passing a template which requires a comma to a single-argument macro

问题描述

我有一些代码基本上可以压缩为

I have some code that essentially condenses down to

#define FOO(a)
FOO(std::map<int, int>);

但是它会发出编译错误（宏 FOO <的实际参数太多了）。

But it emits a compile error (too many actual parameters for macro FOO).

很明显，预处理程序认为我已经提供了 std :: map< int 和 int> 作为参数。

Obviously the preprocessor is thinking that I've supplied std::map<int and int> as arguments.

有办法解决吗？预处理器不会以这种方式用引号引起来的字符串。

Is there a way round this? The preprocessor will not treat a quoted string with a comma in this way.

推荐答案

这在理想情况下应该是注释，但是这样不支持注释中的代码，因此，您可以执行

This should perhaps ideally be a comment, but SO doesn't support code in comments, so, you can do

#include <map>

#define T_ARGS( ... ) < __VA_ARGS__ >

#define FOO( a )  a x;

auto main() -> int
{
    FOO( std::map T_ARGS( int, int ) );
    (void) x;
}

或者您可以定义一个解析为逗号的宏，也可以只使用关于特定于特定用例的任何方案（例如，分别传递模板名称）。

or you can define a macro that resolves to comma, or you can use just about any scheme that's specific to some particular use case (e.g., passing template name separately).

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