C++26 Reflections adventures and compile time UML

Re:C++26 Reflections adventures and compile time UML by dguest on Sunday August 03, 2025 @04:05AM (#44774964)

It would standardize something they've done with a home-brewed tool for decades. They have a library called "reflex" [1] which adds some reflection, and which was (re)written by cannibalizing a lot of llvm code. They actually use the reflection to serialize a lot of the LHC data.

It's kind of neat that it works. It's also can be a bit fidgety: the cannibalized code can cause some issues (which, e.g. prevented C++11 adoption for a while in some experiments), and now CERN depends on bits of an old C++ compiler to read their data. Some may question the wisdom of making a multi-billion dollar dataset depend on the internals of a C++ compiler, but for sure having a standard is better than the ad-hoc solution they rely on now.

[1]: https://indico.cern.ch/event/408139/contributions/979831/att...

[ Parent | on HN ]

Re:C++26 Reflections adventures and compile time UML by oyoman on Sunday August 03, 2025 @05:12AM (#44775248)

The library that you refer is not in use for a long time already. The document you pointed out is from 2006 (you can check the creation date).

Since then, a lot has changed, and now it is all based on cling ( https://root.cern/cling/ ), that originates from clang and llvm. cling is responsible generates the serialization / reflection of the classes needed within the ROOT framework.

[ Parent | on HN ]

Re:C++26 Reflections adventures and compile time UML by dguest on Sunday August 03, 2025 @08:38AM (#44776141)

Good catch: I'm confusing reflex and the cling code that came later. All the issues I mentioned are still there in (or caused by) cling though. Either way standardization in reflection would help.

[ Parent | on HN ]