Portable Use of Variables

[fr33domlover]

Hello,


I'm a bit confused about all the expressive features and ways to use makefile
variables, so just to be sure -

http://www.gnu.org/software/make/manual/html_node/Substitution-Refs.html

Are these uses of variables portable, or should a portable Makefile.am use only
the plain $(var) form without the tricks?



I'm adapting the doxygen Makefile.am from gtkmm (GTK+ C++ binding) for my use,
but they use text functions and variable features a lot with -no-portability,
so I'm trying to make it work with -Wall -Werror. I hope it's worth the
effort :-) Just trying to have a clean makefile...



-- fr33