qt4-mac @4.8.7: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]

[ryandesign (Ryan Carsten Schmidt)]

qt4-mac does not build on Lion (only).

​https://build.macports.org/builders/ports-10.7_x86_64-builder/builds/258347/steps/install-port/logs/stdio

/opt/local/var/macports/build/qt4-mac-3415a329/work/qt-everywhere-opensource-src-4.8.7/include/QtCore/private/../../../src/corelib/kernel/qcore_unix_p.h:312:5: error: ISO C++17 does not allow 'register' storage class specifier [-Wregister]
    register int ret;
    ^~~~~~~~~

So MacPorts has chosen a newer compiler that defaults to C++17, but the qt4-mac codebase is not compatible with C++17.

Even C++11 support is experimental and hidden behind the cxx11 variant.

The solution would seem to be to tell the build to use C++98 (the C++ standard before C++11) unless the cxx11 variant is selected.

I tried to do this by adding this code:

if {![variant_isset cxx11]} {
    compiler.cxx_standard 1998
    configure.cxxflags-append -std=c++98
}

This failed the same way because the build does not seem to honor configure.cxxflags.

Then I tried:

if {![variant_isset cxx11]} {
    compiler.cxx_standard 1998
    configure.cxx-append -std=c++98
}

This failed because the build assumes that configure.cxx is solely the compiler path.

I give up.