C++17 -> C++11

[vasarhelyi]

Dear Angus!

You mention in the documentation that it is relatively easy to downgrade CMakeLists.txt to be compatible with C++11. Could you point me to the right direction in this context? Thank you!

[vasarhelyi]

Hmmm, I see that this has been asked half year ago here: #642
No asnwers since. Any news?

[vasarhelyi]

And also in #614, without answer...

[vasarhelyi]

Some discussions here: #509

[vasarhelyi]

And this says it is in fact not easy but hard work: #487

[vasarhelyi]

Collecting more info, maybe useful for others... So this stated to be working for C++14: reunanen/Clipper2@main...cpp14-compatibility (but not C++11)

[AngusJohnson]

Sorry Gabor, I'm not experienced enough in C++ to help without spending much more time than I can afford.
I'm hoping someone else can help you there.

[vasarhelyi]

Well, as far as I see these are the things not present in C++11:

• std::numeric_limits (that can be resolved with explicit #include <limits>)
• if constexpr that can be replaced to simple if with no major drawback, or replaced to enable_if_t if decision is needed at compile time)
• std::make_unique (that could be defined easily as in e.g. https://stackoverflow.com/questions/24609271/errormake-unique-is-not-a-member-of-std)
• some code in clipper.engine.cpp around make_unique calls, following How to port for C++11/14 #509
• finally: auto& var arguments, that need to be replaced by explicit type (currently I am stuck here as I cannot infer all types from code so far)

Hmmmm. Maybe the "relatively easy" adjective should be removed from the README if you, as the code owner (according to git blame) state that it needs more C++ experience that yours... :)

I also find it kind of difficult to maintain the patch if it is so widespread so if you do not wish to increase compatibility in the main branch and apply these there for eternity than maybe I need to look for a different tool for poly offsetting, unfortunately. Thanks for your reply anyways!

[vasarhelyi]

(final note: we have decided to upgrade ourselves to C++17 instead of abusing you, so problem will hopefully be resolved on our side - thanks anyways :) )

[AngusJohnson]

finally: auto& var arguments, that need to be replaced by explicit type (currently I am stuck here as I cannot infer all types from code so far)

That part I could help you with if your preference is still C++11.

[vasarhelyi]

Note that finally we have created a fork with the only purpose of being CXX11 compatible. See code here: https://github.com/collmot/Clipper2, thanks goes to @ntamas

[ntamas]

FWIW the feat/cpp11-support branch is where the work is being carried out.