Fix 990 / Compilation issues with C++11 and libc++

[heplesser]

Note that the issues fixed here do not occur with gcc and libstdc++, they only occur with LLVM/Clang compilers using libc++ in C++11 mode and with some other compilers that do not use libstdc++.

[heplesser]

@ikitayama @carlosengutierrez This PR should solve the operator=() compilation issues with C++11/libc++. Could you check?

[ikitayama]

@heplesser the build's been going smoothly (97% done), as you know the Fujitsu toolchain takes couples of hours to complete build, so I'll let you know when it's done around midnight here.
I'm a SLI person, so Carlos should check his PyNEST build himself.

[hakonsbm]

Looks good to me, and compiles and runs without problems using both Clang-6.0 and GCC-8 with -std=c++11.

[ikitayama]

confirmation (including make installcheck) will be done sometime tomorrow.

[ikitayama]

@carlosengutierrez are you finished building the 5g branch with FCC natively? Here it's been running for 2 hours, but still going.

[carlosengutierrez]

Hi @ikitayama ,
I am trying to build the branch -->> heplesser:fix-990-c++11-issues (that is the branch to test, right?)
I have to install it by interactive jobs, last night I could reach 97% but connection was broken, now trying again.
Thanks, C.

[ikitayama]

You could use screen so that your build job don't get terminated.

[ikitayama]

@heplesser the cross build with FCC with the -DCMAKE_CXX_FLAGS="-Xg -std=c++11" on the frontend of K computer successfully finished. Took about 3 hours.

[heplesser]

@ikitayama Excellent, thank you!

[heplesser]

I have added another commit, which automatically includes the -std=c++11 compiler flag to CMAKE_CXX_FLAGS before all other flags are processed. This flag appears to be standard for all compilers I checked (gcc, clang, intel, xlc, pgi, fujitsu). While gcc will compile NEST with c++11 features even without this flag, other compilers need it to accept C++11 features.

[suku248]

Alright then, I guess this is ready to be merged.
Thanks @heplesser for solving this issue and thanks @ikitayama and @carlosengutierrez for testing!

[carlosengutierrez]

@heplesser I could compile the updated nest master branch. PYNEST is running.

[heplesser]

@carlosengutierrez Excellent, thank you for testing!