Basic approach
--------------
-The developer is expected to write a makefile fragment in each
-relevant subdirectory called `Subdir.sd.mk'.
+The developer is expected to write a makefile fragment, in each
+relevant subdirectory, called `Subdir.sd.mk'.
These fragments may contain ordinary make language.
Each subdirectory has its own `all' target. For example a
subdirectory `src' has a target `src/all'. The rules for these are
automatically generated from the settings of the per-directory
-&TARGETS variables. (In src/Subdir.sd.mk, this of course refers to a
-make variable called src_TARGETS.)
+&TARGETS variables. &TARGETS is magic in this way. (In
+src/Subdir.sd.mk, &TARGES of course refers to a make variable called
+src_TARGETS.)
The `all' target in a parent directory is taken to imply the `all'
targets in all of its subdirectories, recursively. And in the
You can define other per-directory recursive targets too: simply
mention (usually, by setting) the variable &TARGETS_zonk, or whatever.
-This will create a src/zonk target. (&TARGETS is magic.)
+This will create a src/zonk target.
Unlike `all', these other targets only exist in areas of the project
where at least something mentions them. So for example, if
&TARGETS_zonk is mentioned in src but not lib, `make zonk' in
is already provided in subdirmk, for you to reference like this:
&:include subdirmk/cdeps.sd.mk
&:include subdirmk/clean.sd.mk
-(for example in Perdir.sd.mk).
+For example you could put that in Perdir.sd.mk.
+
+Global definitions
+------------------
+
+If want to set global variables, such as CC, that should only be done
+once. You can put them in your top-level Subdir.sd.mk, or a separate
+file you `include' and declare using SUBDIRMK_MAKEFILES.
Subdirectory templates `.sd.mk' vs plain autoconf templates `.mk.in'
--------------------------------------------------------------------
Processed by &-substitution, autoconf only
then autoconf
+ Instantiated Usu. once per subdir Once only
+
Need to be mentioned No, but Subdir.sd.mk All not in subdirmk/
- in configure.ac via SUBDIRMK_SUBDIRS via SUBDIRMK_MAKEFILES
+ in configure.ac? via SUBDIRMK_SUBDIRS via SUBDIRMK_MAKEFILES
How to include `&:include foo.sd.mk' `include foo.mk'
in all relevant .sd.mk in only one
automatic regeneration for all of this template substitution, and for
config.status etc. is done for you.
-Global definitions
-------------------
-
-If want to set global variables, such as CC, that should only be done
-once. The usual approach is to include
-
-
-
- subdirmk/cdeps.mk.in
- subdirmk/cdeps.mk.in
-
-
-
-
-
-
-
- (None of this prevents
+Substitution syntax
+-------------------
+
+In general & expands to the subdirectory name when used for a
+filename, and to the subdirectory name with / replaced with _ for
+variable names.
+
+Note that & is processed *even in makefile comments*. The substitutor
+does not understand make syntax, or shell syntax, at all. However,
+the substitution rules are chosen to work well with constructs which
+are common in makefiles.
+
+In the notation below, we suppose that the substitution is being in
+done in a subdirectory sub/dir of the source tree. In the RH column
+we describe the expansion at the top level, which is often a special
+case (in general in variable names we call that TOP rather than the
+empty string).
+
+&CAPS => sub_dir_CAPS or TOP_CAPS
+&lc => sub/dir/lc or lc
+ Here CAPS is any ASCII letter A-Z and lc is a-z.
+ The assumption is that filenames are usually lowercase and
+ variables usually uppercase. Otherwise, use another syntax:
+
+&_ => sub_dir_ or TOP_
+&/ => sub/dir/ or nothing
+&=_ => sub_dir or TOP
+&=/ => sub/dir or .
+&^ => $(top_srcdir)/sub/dir or $(top_srcdir)
+&~ => $(abs_top_srcdir)/sub/dir or $(abs_top_srcdir)
+
+&& => && for convenience in shell runes
+\& => & general escaping mechanism
+
+& thing thing... &
+& ^ thing thing... &
+& ~ thing thing... &
+ Convenience syntax for prefixing multiple filenames.
+ Introduced by & followed by lwsp (space or tab).
+ Each lwsp-separated non-ws word is prefixed by &/ &^/ &~/
+ respectively. No other & escapes are recognised.
+ This processing continues until a & preceded by lwsp,
+ or until EOL (the end of the line), or \ then EOL.
-
-
-
-
- https://web.archive.org/web/20150330111905/http://miller.emu.id.au/pmiller/books/rmch/
-
-
-
-
-&CAPS => subdir_CAPS or TOP_CAPS
-&lc => subdir/lc or lc
-
-&_ => subdir_ or TOP_
-&/ => subdir/ or nothing
-&=_ => subdir or TOP
-&=/ => subdir or .
-&^ => $(top_srcdir)/subdir or $(top_srcdir)
-&~ => $(abs_top_srcdir)/subdir or $(abs_top_srcdir)
-
-&& => &&
-\& => &
-
-& thing thing... & => each thing prefixed by &/ &^/ &~/ resp
-& ^ thing thing... & each thing is any non-ws
-& ~ thing thing... & & may be omitted before EOL or before \EOL
- other &'s not recognised
-
-start of line (maybe after ws):
&:<directive> <args>....
-args are processed for & first
-&:include filename filename should usually be foo.mk.in
-&:-include filename
-
-CAPS is [A-Z][0-9_A-Z]*(?!\w)
-lc is [a-z][-+,0-9_a-z]*(?!\w)
-
-&!<spaces or tabs> disables & *until* EOL (and disappears)
-
-&!STUFF<lwsp> STUFF is recognised instead of &
- the terminating lwsp is discarded too
- may also occur at eol
-
-eg notably
- STUFF!& now & is recognised instead (ie back to normal)
- STUFFSTUFF STUFF
-
-eg
- &!@@@ @@@ is recognised instead of &
- @@@!& go back to &
-
-&TARGETS[_things] is handled specially
- must be spelled precisely this way
- if no _things, means _all
-
-Also, `all' is weird in that it is present even if not specified
+ recognised at start of line only (possibly after lwsp)
+ args are processed for &
+
+&:include filename filename should usually be foo.sd.mk
+&:-include filename tolerate nonexistent file
+
+&!<lwsp> disables & until EOL (and then disappears)
+
+&!STUFF
+ changes the escape sequence from & to literally STUFF
+ STUFF may be any series of of non-whitespace characters,
+ and is terminated by EOL or lwsp. STUFF and the lwsp
+ is discarded.
+
+ After this, write STUFF instead of &, everywhere.
+ The effect is global and lasts until the next setting.
+ It takes effect on &:include'd files too, so maybe set
+ it back before using &:include.
+
+ Notably
+ STUFFSTUFF => STUFF
+ \STUFF => STUFF
+ STUFF!& set escape back to &
+
+&TARGETS_things
+ Handled specially. If mentioned, declares that
+ this subdirectory ought to have a target `things'.
+ (`all' if not specified). The rule will be
+ &/things:: $(&TARGETS_things)
+
+ You may extend it by adding more :: rules for the target,
+ but the preferred style is to do things like this:
+ &TARGETS_check += & test-passed.stamp
+
+ It is important to mention &TARGETS_things at least once in
+ the context of each applicable directory, because it arranges
+ that the *parent* will also have a `things' target which
+ recursively implies this directory's `things'.
+
+ Must be spelled exactly &TARGETS_things. &_TARGETS_things,
+ for example, does not work. But mentioning it in a #-comment
+ *does* work because the & filter does not care about comments.
+
+ `all' is extra special: every directory has an `all'
+ target, which corresponds to &TARGETS.
+
+Subdirectory and variable naming
+--------------------------------
+
+The simple variable decoration scheme does not enforce a strict
+namespace distinction between parts of variable names which come from
+subdirectory names, and parts that mean something else.
+
+So it is a good idea to be a bit careful with your directory naming.
+`TOP', names that contain `_', and names that are similar to parts of
+make variables (whether conventional ones, or ones used in your
+project) are best avoided.
+
+If you name your variables in ALL CAPS and your subdirectories in
+lower case with `-' rather than `_', there will be no confusion.
~ian / subdirmk.git / commitdiff