root6 port results in ambiguous include directories after 6.14

[olupton (Olli Lupton)]

With the most recent verison(s) of the root6 port I have had problems compiling local code linking against ROOT.

The problem seems to be that in the default MacPorts installation of root6 the ROOT headers are accessible both at /opt/local/libexec/root6/include/root (returned by root-config --incdir) and /opt/local/include/root{,6}

And since 6.14 at least one header with the same name exists at multiple levels of the header file structure:

MD5 (/opt/local/libexec/root6/include/root/RConfig.h) = c2c2d44a3228fcbf9943048bfca2cb27
MD5 (/opt/local/libexec/root6/include/root/ROOT/RConfig.h) = 5d2a7a998a363947acd947487a666bea

(see e.g. ​https://root.cern.ch/doc/v614/ROOT_2RConfig_8h.html and the non-existence of the same page for 6.12)

When (automatically-generated) code tries to include the latter, i.e. #include <ROOT/RConfig.h>, then, if /opt/local/include is in the include path, /opt/local/include/root/RConfig.h is found instead (with a warning about non-portable filenames because the case doesn't match, -Wnonportable-include-path), and compilation fails because the wrong one of the two RConfig.h is picked up (errors like error: use of undeclared identifier 'R__likely' -- included so hopefully Google finds this ticket).

A minimal workaround is to remove the /opt/local/include/root{,6} symlinks and make sure /opt/local/libexec/root6/include/root is in the include path for compilation. This seems a bit ugly, but so do all the other solutions...

Possibilities I see:

• Remove /opt/local/include/root{,6} symlinks: seems wrong to not have the headers somewhere under /opt/local/include
• Move the headers one directory up the tree under /opt/local/include, i.e. ln -s /opt/local/libexec/root6/include/root/RConfig.h /opt/local/include/RConfig.h repeated for every ROOT header: involves a large number of links, but does integrate ROOT into the /opt/local tree a bit better.
• Consider it a bug on my part that /opt/local/include is in the include path when compiling against ROOT: seems unreasonable, many other packages' headers are only available here.
• Consider it a bug on my part that /opt/local/include comes before /opt/local/libexec/root6/include in the include path: doesn't seem very robust/reasonable to expect all external dependencies to respect this convention