You can see at https://build.opensuse.org/package/live_build_log/home:NicoK:branches:KDE:Extra/kmymoney/openSUSE_Leap_42.3/x86_64, that on openSUSE Leap_42.3 the default compiler is still 4.8. and the build breaks without further notice.. This patch gives the user a clear indication about the root case. Any more issues, which would prevent accepting ?

from https://gcc.gnu.org/projects/cxx-status.html#cxx14 it looks that gcc 5 should have complete c++14 support. On that page there is also a detailed list, what is supported in what version.

From searching the web I got the impression that CMAKE_CXX_STANDARD may work. But for example with gcc 4.8.5 this results into using -std=c++1y.

Another option would be to check if a compiler flag is supported with

include(CheckCXXCompilerFlag)

# Check for standard to use
check_cxx_compiler_flag(-std=c++14 HAVE_FLAG1)
message("c++14 ${HAVE_FLAG1}")
check_cxx_compiler_flag(-std=c++1z HAVE_FLAG2)
message("c++1z ${HAVE_FLAG2}")
check_cxx_compiler_flag(-std=c++1y HAVE_FLAG3)
message("c++1y ${HAVE_FLAG3}")

but this also depends on which level is really required.

gcc 5.3.1 does not work

~/src/kmymoney-build> g++-5 --version
g++-5 (SUSE Linux) 5.3.1 20160301 [gcc-5-branch revision 233849]

[  0%] Automatic MOC for target kmm_payeeidentifier
[  0%] Built target kmm_payeeidentifier_autogen
[  0%] Building CXX object kmymoney/mymoney/payeeidentifier/CMakeFiles  /kmm_payeeidentifier.dir/payeeidentifier.cpp.o

g++-5: error: unrecognized command line option ‘-Wnull-dereference’
g++-5: error: unrecognized command line option ‘-Wunused-const-variable’
g++-5: error: unrecognized command line option ‘-Wmisleading-indentation’
kmymoney/mymoney/payeeidentifier/CMakeFiles/kmm_payeeidentifier.dir/build.make:62: r

We could change e.g.

-Wnull-dereference

to

-Wno-null-dereference

The warnings may be fixed, but this one probably not:

/home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp: In instantiation of ‘AccountsModel::setColumnVisibility(eAccountsModel::Column, bool)::<lambda(auto:3&&, QStandardItem*)> [with auto:3 = AccountsModel::setColumnVisibility(eAccountsModel::Column, bool)::<lambda(auto:3&&, QStandardItem*)>&]’:
/home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp:732:53:   required from here
/home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp:725:34: internal compiler error: Speicherzugriffsfehler
           childItem->removeColumn(ixCol);
                                  ^
Please submit a full bug report,
with preprocessed source if appropriate.
See <http://bugs.opensuse.org/> for instructions.

I think that this patch is required to give gcc users an early indication that they need a newer compiler

In D13838#291816, @habacker wrote:

The warnings may be fixed, but this one probably not:

/home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp: In instantiation of ‘AccountsModel::setColumnVisibility(eAccountsModel::Column, bool)::<lambda(auto:3&&, QStandardItem*)> [with auto:3 = AccountsModel::setColumnVisibility(eAccountsModel::Column, bool)::<lambda(auto:3&&, QStandardItem*)>&]’:
 /home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp:732:53:   required from here
 /home/ralf/src/kmymoney/kmymoney/models/accountsmodel.cpp:725:34: internal compiler error: Speicherzugriffsfehler
            childItem->removeColumn(ixCol);
                                   ^
 Please submit a full bug report,
 with preprocessed source if appropriate.
 See <http://bugs.opensuse.org/> for instructions.

I think that this patch is required to give gcc users an early indication that they need a newer compiler

I think it's clearly seen from the returned error. In my opinion there is no need to additionally warn or inform user to which compiler he should switch or upgrade. It could be that gcc 5 on ArchLinux will work. As you can see the returned error says that bug should be reported against OpenSuse.

see https://bugzilla.opensuse.org/show_bug.cgi?id=1101255

In D13838#292380, @habacker wrote:

see https://bugzilla.opensuse.org/show_bug.cgi?id=1101255

I got this answer:

Ok, so it's a known GCC issue. Fix for the issue was also backported to GCC-5
branch, but probably not fully. Anyway, please update to a newer version of
GCC, GCC-5 branch is out of support.

In D13838#292863, @habacker wrote:

In D13838#292380, @habacker wrote:

see https://bugzilla.opensuse.org/show_bug.cgi?id=1101255

I got this answer:

Ok, so it's a known GCC issue. Fix for the issue was also backported to GCC-5
branch, but probably not fully. Anyway, please update to a newer version of
GCC, GCC-5 branch is out of support.

That's very convenient on their side. They use gcc 5.3.1 while the latest from this branch is 5.5. Those releases are two years apart. I'm not sure if 5.5 or even 5.4 could compile KMyMoney. Nevertheless it's better to update gcc to a supported version.

Could you change required version from 6.0 to 5.4?