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diff --git a/build-aux/Makefile.README.txt b/build-aux/Makefile.README.txt new file mode 100644 index 0000000000..3be7a9d878 --- /dev/null +++ b/build-aux/Makefile.README.txt @@ -0,0 +1,112 @@ +# -*- Mode: markdown -*- + +Autothing 3: The smart way to write GNU Makefiles +================================================= + +Autothing is a thing that does things automatically. + +Ok, more helpfully: Autothing is a pair of .mk Makefile fragments that +you can `include` from your Makefiles to make them easier to write; +specifically, it makes it _easy_ to write non-recursive Makefiles--and +ones that are similar to plain recursive Makefiles, at that! + +Synopsis +-------- + +Write your makefiles of the form: + + topsrcdir ?= ... + topoutdir ?= ... + at.Makefile ?= Makefile # Optional + include $(topsrcdir)/build-aux/Makefile.head.mk + + $(outdir)/%.o: $(srcdir)/%.c: + $(CC) -c -o $@ $< + + $(outdir)/hello: $(outdir)/hello.o + + at.subdirs = ... + at.targets = ... + + include $(topsrcdir)/build-aux/Makefile.tail.mk + +This is similar to, but not quite, the comfortable way that you probably +already write your Makefiles. + +Details +------- + +There are two fundamental things that Autothing provides: + + 1. Variable namespacing + 2. Tools for dealing with paths + +The first is important because globals are bad for composability. + +The second is important because GNU Make is too dumb to know that +`foo/bar/../baz` == `foo/baz`. + +Then, there's something that maybe doesn't belong, but I didn't have the heart +to cut it out: + + 3. A module (plugin) system. + +The module system is "important" because there are very often common bits that +you want to be included in every Makefile, and this gives some structure to +that. + +Requirements: + - A version of GNU Make that supports `undefine`. (TODO: check which version + of GNU Make introduced this feature) + +Inputs: + - In each `Makefile`: + - Before `Makefile.head.mk`: + - Variable (mandatory) : `topoutdir` + - Variable (mandatory) : `topsrcdir` (must not be a subdirectory of `$(topoutdir)`) + - Variable (optional) : `at.Makefile` (Default: `Makefile`) + - Between `Makefile.head.mk` and `Makefile.tail.mk`: + - Variable: `at.targets` (Default: empty) + - Variable: `at.subdirs` (Default: empty) + - Files: + - `${topsrcdir}/build-aux/Makefile.{each,once}.{head,tail}/*.mk` + +Outputs: + - Global: + - Variable (function): `$(call at.is_subdir, parent, child)` + - Variable (function): `$(call at.is_strict_subdir, parent, child)` + - Variable (function): `$(call at.relbase, parent, children...)` + - Variable (function): `$(call at.relto, parent, children...)` + - Variable (function): `$(call at.path, paths...)` + - Variable (function): `$(call at.out2src, paths...)` + - Variable (function): `$(call at.addprefix, prefix, paths...)` + - Per-directory: + - Variable: `$(outdir)` + - Variable: `$(srcdir)` + +TODO: actually explain things. + +Motivation/Exposition +--------------------- + +This section needs rewritten. Or really just written. + +Other projects like GNU Automake were created to plaster over differences +between make(1) implementations; however, this isn't all that Automake +provides, it also makes it easy to do complex things that users want, or the +GNU Coding Standards require. That's silly. + +Autothing does depend on GNU Make; other make(1) implementations will +not work. However, if you are open to adding GNU Make as a +dependency, then Autothing should obviate the need for GNU Automake, +while also making your Makefiles better. + + Peter Miller (1997) "Recursive Make Considered Harmful" + <http://aegis.sourceforge.net/auug97.pdf> + +---- +Copyright (C) 2016 Luke Shumaker + +This documentation file is placed into the public domain. If that is +not possible in your legal system, I grant you permission to use it in +absolutely every way that I can legally grant to you. |