如何通过C ++宏调用编译时错误？

Question

The idea is to cause a compile-time error with an error message if a certain macro is invoked . Can this be done? How?

#ifdef RUBBISH_COMPILER
#  define alignof(T)  // what here?
#endif

const std::size_t = alignof(some_type);  // invocation, causing compilation error

The invocation shall produce a sensible error message like alignof() not available with this compiler .

Answer 1

In C++11,

#define DONT_INVOKE_ME static_assert(false, "Don't invoke this macro");

Historically, it was easy to cause an error, but trickier to get a message into the output. One simple trick was to create an invalid declaration, with the message in the declared name:

#define DONT_INVOKE_ME char dont_invoke_this_macro[-1];

This isn't perfect, as you can't use freeform text for the message - it must be a valid identifier. There were fancier tricks (such as those used by Boost's static assert), but they're only of historical interest these days.