Question

I need to have multi-line comments within a group of macros so that one of the macros initiates a comment block and another concludes it, like this:

#define C_BEGIN /*
#define C_END */
... other macros

But sure enough, this approach doesn’t work.

Answer 1

You can’t do it for the following reasoning. Let’s assume it is possible.

So you created a macro that replaces itself with /*, and another for */. What happens then? First, the comments are removed from the code. After that, the preprocessor replaces your macros with the comments. After that, the compiler will choke: it doesn’t know what to do with /* and */ because it simply never faces such things: the comments are always delete before the compilation, so it doesn’t even know what a “comment” is. It will probably think it’s a division followed by multiplication.

So our assumption is wrong and you can’t do it.