Has anyone ever had a use for the __COUNTER__ pre-processor macro?

Question

The __COUNTER__ symbol is provided by VC++ and GCC, and gives an increasing non-negative integral value each time it is used.

I\'m interested to learn w

Answer 1

I'm interested to learn whether anyone's ever used it,

Yes, but as you can see from many examples in this Q&A, __LINE__, which is standardized, would also be sufficient in most cases.

__COUNTER__ is only really necessary in cases where the count must increase by one each time, or it must have continuity over several #include files.

and whether it's something that would be worth standardising?

__COUNTER__, unlike __LINE__, is very dangerous because it depends on which header files are included and what order. If two .cpp files (translation units) include a header file that use __COUNTER__, but the header file obtains different count sequences in the different instances, they may use different definitions of the same thing and violate the one-definition rule.

One-definition rule violations are very difficult to catch and potentially create bugs and security risks. The few use-cases of __COUNTER__ don't really outweigh the downside and lack of scalability.

Even if you never ship code that uses __COUNTER__, it can be useful when prototyping an enumeration sequence, saving you the trouble of assigning names before the membership is concrete.