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The hidden compile-time cost of C++26 reflection

4 points by SuperV1234

by SuperV1234

0 subcomment

I ran some more measurements using import std; with a properly built module that includes reflection.
I first created the module via:
```
  g++ -std=c++26 -fmodules -freflection -fsearch-include-path -fmodule-only -c bits/std.cc 
```
And then benchmarked with:
```
  hyperfine "g++ -std=c++26 -fmodules -freflection ./main.cpp"
```
The only "include" was import std;, nothing else.
These are the results:
- Basic struct reflection: 352.8 ms
- Barry's AoS -> SoA example: 1.077 s
Compare that with PCH:
- Basic struct reflection: 208.7 ms
- Barry's AoS -> SoA example: 1.261 s
So PCH actually wins for just <meta>, and modules are not that much better than PCH for the larger example. Very disappointing.