Try removing attempt to set the C++ standard

[dmah42]

Fixes #1460 #1462

Let's see what the buildbots make of this.

[LebedevRI]

No, this is wrong.

[dmah42]

No, this is wrong.

it's just a draft because i want to see what happens... the compiler used should be free to set it's standard. we already had a fallback to c++0x so the only issue i think would be if someone tries to use a compiler that doesn't support c++11.

if we want to require that then setting CMAKE_CXX_STANDARD and maybe REQUIRED is the way to do that.. but i just want to see how necessary it is.

[LebedevRI]

There is absolutely no requirement that a supported compiler version actually happens
to have the right (the one you expect, and everyone expects different things) default standard.

[dmah42]

first test complete: OSX falls back too far beyond C++11.

next up: setting the standard.

[LebedevRI]

https://cmake.org/cmake/help/latest/policy/CMP0067.html might be relevant.

[dmah42]

https://cmake.org/cmake/help/latest/policy/CMP0067.html might be relevant.

nice :)

[LebedevRI]

Probably also want CMAKE_CXX_EXTENSIONS OFF

[dmah42]

yeah.. i'm also eyeing up the check where we:

set(EXTRA_CXX_FLAGS "")
if (WIN32 AND "${CMAKE_CXX_COMPILER_ID}" MATCHES "Clang")
  # Clang on Windows fails to compile the regex feature check under C++11
  set(EXTRA_CXX_FLAGS "-DCMAKE_CXX_STANDARD=14")
endif()

and wondering how that will end up interacting with this change.

[powderluv]

yes FWIW we need this check for clang on windows.

[dmah42]

https://cmake.org/cmake/help/latest/policy/CMP0067.html might be relevant.

nice :)

cmake 3.8+ only .. ubuntu 16.04 is still on 3.5.1: https://launchpad.net/ubuntu/xenial/+source/cmake

[dmah42]

try_compile also doesn't support setting the standard in 3.5.1.

so our older platform support requires explicit --std flag setting, i think... and for consistency, it suggests we need to do the same in the rest of the project.

until we can drop older platforms, i don't think we can embrace updated cmake norms...

any other ideas, @LebedevRI ?

[LebedevRI]

cmake 3.5.1 sounds really ancient.
Even debian old-old-stable has 3.7.
I think 3.13 should be an unambiguous dependency.

[dmah42]

ubuntu bionic (the oldest LTS ubuntu we support) is 3.10.2 (https://packages.ubuntu.com/bionic/cmake) so i think we can get past 3.8.

it might mean dropping the 14.04 and 16.04 bots but they are really old at this point and we do have a policy on dependencies for a reason.

[LebedevRI]

Sounds reasonable?

[sergiud]

This is not meaningful. MSVC, for instance, does not provide exclusive C++11 support, only C++14 and later: https://docs.microsoft.com/en-us/cpp/build/reference/std-specify-language-standard-version?view=msvc-170. CMake will probably decay to the newer standard anyway.

[dmah42]

Sounds reasonable?

seems like we might just have had our hand forced...

[LebedevRI]

@dmah42 what's the status here?

[dmah42]

@dmah42 what's the status here?

i don't remember where i got to. let me see if i can resurrect it.

[dmah42]

it builds and passes tests but I'm not sure it's the right thing to do. I would appreciate an ack.

[LebedevRI]

it builds and passes tests but I'm not sure it's the right thing to do. I would appreciate an ack.

Given that we don't want to just happen to build under whatever the standard is default
for the compiler that is used, but specifically with C++11, this is the right thing to do.

[LebedevRI]

LG

[dmah42]

merged.. now let's see if anyone finds an issue on any unusual platforms with it.