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

4 days ago

C++26 reflection is a powerful feature, but its compile-time impact is a concern.
Fast compilation times are crucial for productivity and motivation in C++ development.
The Standard Library, not language features like templates, is the main bottleneck for compilation speed.
Using minimal Standard Library can drastically reduce compilation times, as shown by a fork of SFML compiling in ~4.3s.
Reflection in C++26 is not purely a lightweight language feature, impacting compile times.
Benchmarking GCC 16 with reflection shows varying compile times based on usage scenarios.
Including `<meta>` adds ~310 ms, while `<ranges>` and `<print>` add significant overhead.
Precompiled headers (PCH) are essential for scaling reflection usage, reducing compile times significantly.
Modules show potential but currently do not outperform PCH in reducing compile times.
Reflection will likely lead to widespread use of `<meta>` and other dependencies, increasing compile overhead.
The author advocates for minimizing Standard Library dependencies to improve compilation speed and productivity.

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