maintainer-feedback requested: [Bug 219862] devel/cmake: Cmake 3.8.0 somehow is unaware about CXX17 dialect

[bugzilla-noreply at freebsd.org]

Aleksander Alekseev <afiskon at devzen.ru> has reassigned Bugzilla Automation
<bugzilla at FreeBSD.org>'s request for maintainer-feedback to kde at FreeBSD.org:
Bug 219862: devel/cmake: Cmake 3.8.0 somehow is unaware about CXX17 dialect
https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=219862



--- Description ---
Hi!

I've just installed cmake 3.8.0 using ports tree with default options (sudo
make -DBATCH install clean). Then I tried to build a simple project that uses
C++17 features:

```
git clone https://github.com/afiskon/cpp-multithreading.git
cd cpp-multithreading
mkdir build
cd build
cmake ..
```

Here is the output:

```
-- The C compiler identification is Clang 3.8.0
-- The CXX compiler identification is Clang 3.8.0
-- Check for working C compiler: /usr/bin/cc
-- Check for working C compiler: /usr/bin/cc -- works
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Detecting C compile features
-- Detecting C compile features - done
-- Check for working CXX compiler: /usr/bin/CC
-- Check for working CXX compiler: /usr/bin/CC -- works
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done
CMake Error in CMakeLists.txt:
  Target "atomic_example" requires the language dialect "CXX17" (with
  compiler extensions), but CMake does not know the compile flags to use to
  enable it.


CMake Error in CMakeLists.txt:
  Target "shared_mutex_example" requires the language dialect "CXX17" (with
  compiler extensions), but CMake does not know the compile flags to use to
  enable it.


CMake Error in CMakeLists.txt:
  Target "mutex_example" requires the language dialect "CXX17" (with compiler
  extensions), but CMake does not know the compile flags to use to enable it.


-- Generating done
-- Build files have been written to: /home/eax/cpp-multithreading/build
```

This looks like a bug since CMake 3.8.0 on Linux (tested on Ubuntu 16.04 and
Arch Linux, on GCC and Clang) builds the same project without problems.