diff options
Diffstat (limited to 'build-aux/Makefile.README.txt')
| -rw-r--r-- | build-aux/Makefile.README.txt | 262 |
1 files changed, 105 insertions, 157 deletions
diff --git a/build-aux/Makefile.README.txt b/build-aux/Makefile.README.txt index e06ba52..3be7a9d 100644 --- a/build-aux/Makefile.README.txt +++ b/build-aux/Makefile.README.txt @@ -1,160 +1,108 @@ -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`. +# -*- 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 |