Reflection for C++26

Having implemented reflection in languages like C(++), before, it is most certainly not bloat-free. There are sorts of 'obvious' things programmers do (like enum-reflection) that end up injecting strings all over the place. The overhead is (worst case) proportional to the source-code size, in those cases. In other cases, you end up with bloat proportional to heavily-utilized template libraries. However, unless the reflection system is very clever, i.e., exposes enough information to the linker to strip duplicate-ish symbols, you end up with a bunch of reflection copies.

extern templates address the issue of having multiple instances of a template being expanded inline, with only minimal mess and fuss. (A way to prevent inlining of templated code would have been nice too).

I always thought it’s good practice in C/C++ to have only one translation unit in release builds e.g. SQLite amalgamations, instead of relying on LTO. It also speeds up compilation because it isn’t recompiling the same header files over and over again.

It's a cute idea but just not scalable. It doesn't speed up compilation because separate translation units can be compiled independently and cached.

That's called a "unity build", build systems such as cmake support it. It has its pros and cons.

Do things that don’t scale :)

Obviously it’s not suitable for dev builds, I don’t think anyone uses it for that. For release builds you would want to clear caches anyway.

And while it helps with compile time (especially with mediocre compilers like MSVC where a large time is spent in the front-end), it doesn't help with stripping unneeded code/data compared to LTO.

It does significantly speed up clean builds in many cases, to the point that those clean builds can even be faster than many "incremental" builds in some cases.

I do not know of any compiler that can compile different parts of a translation unit in parallel. But plenty of systems (including the venerable `make -j`) can compile separate translation units in parallel because they are independent.

You don't want to clear caches for release builds. That just makes release builds unnecessarily slow and impedes the flow of Continuous Deployment. You just need to have separate caches for different build flags, including a dedicated cache for release builds.