Installing doctest using cmake and make fails on Ubuntu 16.04 (C++11 is not used)

[Dobiasd]

When trying to install doctest naively like this:

git clone https://github.com/onqtam/doctest
cd doctest
mkdir -p build
cd build
cmake ..
make install

I get compiler errors from the fact, that it tried to compile without setting the -std=c++11 flag.

In file included from /home/tobias/doctest/examples/all_features/main.cpp:2:0:
/home/tobias/doctest/examples/all_features/../../doctest/doctest.h:392:1: error: identifier ‘decltype’ is a keyword in C++11 [-Werror=c++0x-compat]
 typedef decltype(nullptr) nullptr_t;

Full output here: https://gist.github.com/Dobiasd/6146ff7ea3ebe0261cbe45b27db0bebd

When I git checkout tags/1.2.9 instead, it works, but I'd like to upgrade my two libraries (FunctionalPlus, and frugally-deep) to the latest version.

My test machine is basically an Ubuntu 16.04:

$ cat /etc/linuxmint/info
RELEASE=18.2
CODENAME=sonya
EDITION="Cinnamon 64-bit"
DESCRIPTION="Linux Mint 18.2 Sonya"
DESKTOP=Gnome
TOOLKIT=GTK
NEW_FEATURES_URL=http://www.linuxmint.com/rel_sonya_cinnamon_whatsnew.php
RELEASE_NOTES_URL=http://www.linuxmint.com/rel_sonya_cinnamon.php
USER_GUIDE_URL=help:linuxmint
GRUB_TITLE=Linux Mint 18.2 Cinnamon 64-bit

The compilers are new enough to support C++11:

$ g++ --version
g++ (Ubuntu 5.4.0-6ubuntu1~16.04.11) 5.4.0 20160609
Copyright (C) 2015 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ clang++ --version
clang version 3.8.0-2ubuntu4 (tags/RELEASE_380/final)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

What is the recommended way to install doctest using cmake? I was unable to find it in the docs.

[onqtam]

Sooo it seems that it is not the installing, but the building of the examples that fails.

doctest 2.0 uses C++11. Also it uses -Weverything for clang for building the examples and later disables a few flags which aren't compatible - like c++98-compat:
https://github.com/onqtam/doctest/blob/master/scripts/cmake/common.cmake#L154

I now see that on Travis CI I explicitly tell CMake to use C++11 like this:
https://github.com/onqtam/doctest/blob/master/.travis.yml#L332

and later like this:

https://github.com/onqtam/doctest/blob/master/.travis.yml#L340

Both of the compilers you are using support some (or even most) of C++11, but for them the default std is still 98 - I think that changed for GCC 6 and perhaps a newer clang as well.

So try explicitly setting the standard to C++11 and let me know if it works - I might think of a solution inside of the repository if this is indeed the problem.

[Dobiasd]

Thanks for the quick help. I'm now using the following, and it works perfectly:

git clone https://github.com/onqtam/doctest
cd doctest
mkdir -p build
cd build
cmake .. -DCMAKE_CXX_FLAGS=-std=c++11
make install