clarifications of some patched items

[olesenm]

Hi @mrklein - some small questions

 template<class T>
 void Foam::shuffle(UList<T>& a)
 {
-    std::random_shuffle(a.begin(), a.end());
+    std::random_device rd;
+    std::mt19937 g(rd());
+    std::shuffle(a.begin(), a.end(), g);
 }

Any particular issue or cost/benefit of this change?

[mrklein]

Hi,

random_shuffle is deprecated in C++14 and C++14 was necessary for new CGAL.

Code was taken from an example at cppreference (https://en.cppreference.com/w/cpp/algorithm/random_shuffle) without much thought.

[olesenm]

Ah, it would have paid for me to read the docs. Will update random_shuffle upstream accordingly. The c++14 change required for CGAL is known, but we are still playing the balancing act of keeping the requirements down (eg, centos7 only ships with gcc 4.8.5) while still moving forward. This also means that we ship with a slightly older CGAL for now. Patching the wmake rules to use c++14 (as you have done) makes the best sense for now to use newer system CGAL version. It's also what we do for the Ubuntu packages.

Thanks for the explanation!