[maccard]

This is super unrelated to the optimisation, and is just related to the cmake setup - instead of common.hpp having #ifdef USE_NOEXCEPT #define NOEXCEPT noexcept #else #define NOEXCEPT #endif

and cmake being:

    if (WITH_NOEXCEPT)
      message(STATUS "Using `noexcept` annotations (faster?)")
      target_compile_definitions(PSRayTracing_StaticLibrary PUBLIC USE_NOEXCEPT)
    else()
      message(STATUS "Turned off use of `noexcept` (slower?)")
    endif()

, the cmake could just be:

    if (WITH_NOEXCEPT)
      message(STATUS "Using `noexcept` annotations (faster?)")
      target_compile_definitions(PSRayTracing_StaticLibrary PUBLIC USE_NOEXCEPT=noexcept)
    else()
      message(STATUS "Turned off use of `noexcept` (slower?)")      target_compile_definitions(PSRayTracing_StaticLibrary PUBLIC USE_NOEXCEPT=)
    endif()

No need for these shared "common" config headers.

Back on topic, this doesn't surprise me. There's this idea that C++ is fast, and that people who work with C++ are focused on optimisation and in my experience there's as many of these theoretical ideas about performance which aren't backed up by numbers, but are now ingrained in people. See https://news.ycombinator.com/item?id=41095814 from last week for another example of dogmatic guidelines having the wrong impact.