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diff --git a/build-aux/Makefile.README.txt b/build-aux/Makefile.README.txt new file mode 100644 index 0000000000..e06ba523d4 --- /dev/null +++ b/build-aux/Makefile.README.txt @@ -0,0 +1,164 @@ +Luke's AutoMake +=============== + +Yo, this document is incomplete. It describes the magical +automake.{head,tail}.mk Makefiles and how to use them, kinda. + +I wrote a "clone" of automake. I say clone, because it works +differently. Yeah, I need a new name for it. + +High-level overview +------------------- + +Now, what this does for you is: + +It makes it _easy_ to write non-recursive Makefiles--and ones that are +similar to plain recursive Makefiles, at that! (search for the paper +"Recursive Make Considered Harmful") As harmful as recursive make is, +it's historically been difficult to to write non-recursive Makefiles. +This makes it easy. + +It also makes it easy to follow the GNU standards for your makefiles: +it takes care of this entire table of .PHONY targets for you: + +| this | and this | are aliases for this | +|------+------------------+--------------------------------------------------------| +| all | build | $(outdir)/build | +| | install | $(outdir)/install | +| | uninstall | $(outdir)/uninstall | +| | mostlyclean | $(outdir)/mostlyclean | +| | clean | $(outdir)/clean | +| | distclean | $(outdir)/distclean | +| | maintainer-clean | $(outdir)/maintainer-clean | +| | check | $(outdir)/check (not implemented for you) | +| | dist | $(topoutdir)/$(PACKAGE)-$(VERSION).tar.gz (not .PHONY) | + +(You are still responsible for implementing the `$(outdir)/check` +target in each of your Makefiles.) + +What you have to do is: + +In each source directory, you write a `Makefile`, very similarly to if +you were writing for plain GNU Make, with + + topoutdir ?= ... + topsrcdir ?= ... + include $(topsrcdir)/build-aux/Makefile.head.mk + + # your makefile + + include $(topsrcdir)/build-aux/Makefile.tail.mk + +And in the top-level source directory, Write your own helper makefiles +that get included: + - `common.once.head.mk`: before parsing any of your Makefiles + - `common.each.head.mk`: before parsing each of your Makefiles + - `common.each.tail.mk`: after parsing each of your Makefiles + - `common.each.tail.mk`: after parsing all of your Makefiles + +The `common.*.mk` makefiles are nice for including generic pattern +rules and variables that aren't specific to a directory. + +You're probably thinking that this sounds too good to be true! +Unfortunately, there are two major deviations from writing a plain +recursive Makefile: + + 1. all targets and prerequisites (including .PHONY targets!) need to + be prefixed with + `$(srcdir)`/`$(outdir)`/`$(topsrcdir)`/`$(topoutdir)`. + * sub-gotcha: this means that if a pattern rule has a + prerequisite that may be in srcdir or outdir, then it must be + specified twice, once for each case. + 2. if a prerequisite is in a directory "owned" by another Makefile, + you must filter the pathname through `am_path`: + `$(call am_path,YOUR_PATH)`. Further, that path must NOT contain + a `..` segment; if you need to refer to a sibling directory, do it + relative to `$(topoutdir)` or `$(topsrcdir)`. + +Telling automake about your program +----------------------------------- + +You tell automake what to do for you by setting some variables. They +are all prefixed with `am_`; this prefix may be changed by editing the +`_am` variable at the top of `automake.head.mk`. + +The exception to this is the `am_path` variable, which is a macro that +is used to make a list of filenames relative to the appropriate +directory, because unlike normal GNU (Auto)Make, `$(outdir)` isn't +nescessarily equal to `.`. See above. + +There are several commands that generate files; simply record the list +of files that each command generates as the following variable +variables: + +| Variable | Create Command | Delete Command | Description | Relative to | +|--------------+----------------+-----------------------------+-----------------------------------+-------------| +| am_src_files | emacs | rm -rf . | Files that the developer writes | srcdir | +| am_gen_files | ??? | make maintainer-clean | Files the developer compiles | srcdir | +| am_cfg_files | ./configure | make distclean | Users' compile-time configuration | outdir | +| am_out_files | make all | make mostlyclean/make clean | Files the user compiles | outdir | +| am_sys_files | make install | make uninstall | Files the user installs | DESTDIR | + +In addition, there are two more variables that control not how files +are created, but how they are deleted: + +| Variable | Affected command | Description | Relative to | +|----------------+------------------+------------------------------------------------+-------------| +| am_clean_files | make clean | A list of things to `rm` in addition to the | outdir | +| | | files in `$(am_out_files)`. (Example: `*.o`) | | +|----------------+------------------+------------------------------------------------+-------------| +| am_slow_files | make mostlyclean | A list of things that (as an exception) should | outdir | +| | | _not_ be deleted. (otherwise, `mostlyclean` | | +| | | is the same as `clean`) | | + +Finally, there are two variables that express the relationships +between directories: + +| Variable | Description | +|------------+---------------------------------------------------------| +| am_subdirs | A list of other directories (containing Makefiles) that | +| | may be considered "children" of this | +| | directory/Makefile; building a phony target in this | +| | directory should also build it in the subdirectory. | +| | They are not necesarily actually subdirectories of this | +| | directory in the filesystem. | +|------------+---------------------------------------------------------| +| am_depdirs | A list of other directories (containing Makefiles) that | +| | contain or generate files that are dependencies of | +| | targets in this directory. They are not necesarily | +| | actually subdirectories of this directory in the | +| | filesystem. Except for files that are dependencies of | +| | files in this directory, things in the dependency | +| | directory will not be built. | + +Tips, notes +----------- + +I like to have the first (non-comment) line in a Makefile be: + + include $(dir $(lastword $(MAKEFILE_LIST)))/../../config.mk + +(adjusting the number of `../` sequences as nescessary). Then, my +(user-editable) `config.mk` is of the form: + + ifeq ($(topsrcdir),) + topoutdir := $(patsubst %/,%,$(dir $(lastword $(MAKEFILE_LIST)))) + topsrcdir := $(topoutdir) + + # your configuration + + endif + +If the package has a `./configure` script, then I have it modifiy +topsrcdir as necessary, as well as modifying whatever other parts of +the configuration. All of the configuration lives in `config.mk`; +`./configure` doesn't modify any `Makefile`s, it just generates +`config.mk`, and copies (or (sym?)link?) every `$(srcdir)/Makefile` to +`$(outdir)/Makefile`. + +---- +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. |