This may lead to hard-to-track bugs when someone has incompatible C-specific CFLAGS set. It's probably better to collect
all the -I includes in a separate variable and add that to both CFLAGS and CXXFLAGS.

Downstream Gentoo bug for reference: https://bugs.gentoo.org/show_bug.cgi?id=396281

Date: 2012-05-27 09:34
Sender: Hans de Graaff

For reference, I have filed a bug for this with the ruby
project: https://bugs.ruby-lang.org/issues/6504

Date: 2012-02-01 17:47
Sender: Lars Kanis

Thanks for the bug report. This is not a bug in FXRuby, but in
the Ruby std.lib "mkmk.rb". The logic that Ruby uses
for compiling C++ extensions is just $CXXFLAGS = $CFLAGS + ...
See also: https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L17
61

It seems to be a bigger change to proper respect CXXFLAGS there.
FXRuby could poke around it, but this would possibly break other
build environments.