[ainar-g]

One person's obtuseness is other person's simplicity :-) . In all of my personal and some of my work projects I used nothing but portable features in Shell, Make, Sed, etc. Checking with multiple implementations where possible. As long as you use the right tool for the right job, there shouldn't be any problems.

The most common mistake of that sort that I've seen is people trying to do complex conditionals inside their makefiles when they clearly would be better off in a Shell script. (I'm looking at you, fans of ifeq.)

[wahern]

You can implement conditionals semi-portably. See https://github.com/wahern/autoguess/blob/master/Makefile.gue..., which works with GNU Make, NetBSD/FreeBSD make, OpenBSD make, and Solaris make. Alas, it doesn't work with AIX's native make.

Once POSIX standardizes "!=" then POSIX-portable conditionals will be possible using the same technique as above, replacing, e.g. OS = $(shell $(OS.exec))$(OS.exec:sh) with just OS != $(OS.exec). Though, you'd need to wait for Solaris, AIX, and macOS gmake[1] to add support for !=.

Alternatively, if you add an extra level of indirection using .DEFAULT to capture and forward make invocations, you can simply pass OS, etc, as invocation arguments. Indirection solves everything, though, so that's cheating.

[1] Apple's ancient GNU Make 3.81 predates != support. :(