Trying out C++20's modules with Clang and Make

Re:Trying out C++20's modules with Clang and Make by vblanco on Sunday October 15, 2023 @12:50PM (#37891319)

Yes, but template code is all on headers, so it gets parsed every single time its included on some compile unit. With modules this only happens once so its a huge speed upgrade in pretty much all cases.

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Re:Trying out C++20's modules with Clang and Make by moregrist on Sunday October 15, 2023 @01:07PM (#37891480)

Whenever I’ve profiled compile times, parsing accounts for relatively little of the time, while the vast majority of the time is spent in the optimizer.

So at least for my projects it’s a modest (maybe 10-20%) speed up, not the order of magnitude speed up I was hoping for.

Thus C++ compile times will remain abysmal.

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Re:Trying out C++20's modules with Clang and Make by dagmx on Sunday October 15, 2023 @01:59PM (#37891880)

For some template heavy code bases I’ve been in, going to PCH has cut my compile times to less than half. I assume modules will have a similar benefit in those particular repositories, but obviously YMMV

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