`subdirmk' is an attempt to solve these problems (and it also slightly
alleviates some of the boilerplate needed to support out-of-tree
-builds well).
+builds well, and helps a bit with metaprogramming and rule writing).
Basic approach
--------------
Where there are dependencies between subdirectories, each Dir.sd.mk
can simply refer to files in other subdirectories directly.
+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. (If your variables start with capital letters and
+your filenames with lowercase. Otherwise, use &/ or &_.)
+
+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 nothing
+&_ => sub_dir_ or TOP_
+&. => sub/dir or .
+ (This implies that `&./' works roughly like `&/', although
+ it can produce a needless `./')
+
+&= => sub_dir or TOP
+
+&^lc => $(top_srcdir)/sub/dir/lc
+&^/ => $(top_srcdir)/sub/dir/
+&^. => $(top_srcdir)/sub/dir
+
+&~lc => $(top_srcdir)/lc
+&~/ => $(top_srcdir)/
+&~. => $(top_srcdir)
+
+In general:
+ ^ pathname of this subdirectory in source tree
+ ~ pathname of top level of source tree
+ / terminates the path escape } needed if next is
+ _ terminates the var escape } not letter or space)
+ . terminates path escape giving dir name (excluding /)
+ = terminates var escape giving only prefix part (rarely needed)
+ lwsp starts multi-word processing (see below)
+
+So pathname syntax is a subset of:
+ '&' [ '^' | '~' ] [ lc | '/' | '.' ]
+
+&& => && for convenience in shell runes
+
+&\& => & general escaping mechanism
+&\$ => $ provided for $-doubling regimes
+&\NEWLINE eats the newline and vanishes
+
+&$VARIABLE => $(sub_dir_VARIABLE) or $(TOP_VARIABLE)
+ VARIABLE is ASCII starting with a letter and matching \w+
+
+& thing thing... &
+&^ thing thing... &
+&~ thing thing... &
+ Convenience syntax for prefixing multiple filenames.
+ Introduced by & followed by lwsp where lc could go.
+ Each lwsp-separated non-ws word is prefixed by &/ etc.
+ etc. respectively. No other & escapes are recognised.
+ This processing continues until & preceded by lwsp,
+ or until EOL (the end of the line), or \ then EOL.
+
+&:<directive> <args>....
+ recognised at start of line only (possibly after lwsp)
+
+&:include filename filename should usually be [&]foo.sd.mk
+&:-include filename tolerate nonexistent file
+ RHS is &-expanded but filenames are relative to the top
+ srcdir. This implies that unqualified names are like &~/
+ whereas &/ is like &^/. &^ and &~ do not work here because
+ they expand to constructions involving literally
+ `$(top_srcdir)', but the RHS is not make-expanded.
+
+&!<lwsp> disables & until EOL (and then disappears)
+
+&# delete everything to end of line
+ (useful if the RHS contains unrecognised & constructions)
+
+&TARGETS_things
+ Handled specially. If mentioned at the start of a line
+ (possibly following whitespace), declares that this
+ subdir ought to have a target `things'. 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 doing so
+ 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, is not magic. To make the target exist
+ without providing any prerequisites for it, write a line
+ containing just `&TARGETS_things +='.
+
+ `all' is extra special: every directory has an `all'
+ target, which corresponds to &TARGETS.
+
+&:warn [!]WARNTAG ...
+ Suppress (with !) or re-enable (without !) warnings tagged
+ WARNTAG (see section `Warnings', below). The suppression list
+ is reset at the start of processing in each subdirectory.
+ Warnings that appear at the end of processing are controlled
+ by the final warning state after processing all the toplevel
+ input files (including Final.sd.mk).
+
+&:local+global [&]VARIABLE ...
+ Suppresses the warning about seeing both VARIABLE and
+ &VARIABLE. Any & specified in the RHS is redundant: this
+ always affects both versions identically.
+
+&:changequote NEWQUOTE
+ changes the escape sequence from & to literally NEWQUOTE
+ NEWQUOTE may be any series of of non-whitespace characters,
+ and is terminated by EOL or lwsp. The whole line is
+ discarded.
+
+ After this, write NEWQUOTE instead of &, everywhere.
+ The effect is unscoped and lasts until the next setting,
+ or until the end of the current directory's Suffix.sd.mk.
+ It takes effect on &:include'd files too, so maybe set
+ it back before using &:include.
+
+ Notably
+ NEWQUOTENEWQUOTE => NEWQUOTENEWQUOTE
+ NEWQUOTE\NEWQUOTE => NEWQUOTE
+ NEWQUOTE\$ => $
+ NEWQUOTE:changequote & set escape back to &
+
+
+Dollar doubling and macro assistance
+------------------------------------
+
+&$+ Starts dollar-doubling
+&$- Stops dollar-doubling
+ Both are idempotent and local to the file or context.
+
+Sometimes we will show $'s being doubled inside another construct.
+This means the content of the construct is $-doubled: $-doubling is
+locally enabled, and restored afterwards.
+
+&:macro NAME => define NAME
+STUFF $ THINGS .. STUFF $$ THINGS
+&:endm .. endef
+ NAME is processed for &
+
+&${..$..} => ${eval ${call ..$$..}}
+ (matches { } pairs to find the end)
+ content is $-doubled (unless it contains $- to turn that off)
+
+ Together &:macro and &${...} provide a more reasonable macro
+ facility than raw make. They solve the problem that make
+ expansions cannot directly generate multiple rules, variable,
+ etc.; instead, `$(eval )' must be used, but that re-expands
+ the argument, meaning that all the literal text must be
+ $-doubled. This applies to the macro text and to the
+ arguments. Also `$(eval $(call ...))' is an unfortunate syntax.
+ Hence &:macro and &${...}.
+
+While dollar-doubling:
+- - - - - - - - - - -
+
+$ => $$ including $'s produced by other
+ &-expansions not mentioned here
+
+&\$ => $
+&$NN => $(NN) where N are digits
+&$( => $(
+
+A few contexts do not support $-doubling, such as directive arguments
+or places where this might imply $-quadrupling. (There is no way to
+get $-quadrupling.)
+
+
Invocation, "recursive" per-directory targets
---------------------------------------------
automatic regeneration for all of this template substitution, and for
config.status etc. is done for you.
+
Tables of file reference syntaxes
---------------------------------
(This assumes you have appropriate make variables src, PWD and
abs_src.)
-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 nothing
-&_ => sub_dir_ or TOP_
-&. => sub/dir or .
- (This implies that `&./' works roughly like `&/', although
- it can produce a needless `./')
-
-&= => sub_dir or TOP
-
-&^lc => $(top_srcdir)/sub/dir/lc
-&^/ => $(top_srcdir)/sub/dir/
-&^. => $(top_srcdir)/sub/dir
-
-&~lc => $(top_srcdir)/lc
-&~/ => $(top_srcdir)/
-&~. => $(top_srcdir)
-
-In general:
- ^ pathname of this subdirectory in source tree
- ~ pathname of top level of source tree
- / terminates the path escape } needed if next is
- _ terminates the var escape } not lwsp or space)
- . terminates path escape giving dir name (excluding /)
- = terminates var escape giving only prefix part (rarely needed)
- lwsp starts multi-word processing (see below)
-
-So pathname syntax is a subset of:
- '&' [ '^' | '~' ] [ lc | '/' | '.' | '=' ]
-
-&& => && for convenience in shell runes
-
-&\& => & general escaping mechanism
-&\$ => $ provided for $-doubling regimes
-&\NEWLINE eats the newline and vanishes
-
-&$VARIABLE => $(sub_dir_VARIABLE) or $(TOP_VARIABLE)
- VARIABLE is ASCII starting with a letter and matching \w+
-
-& thing thing... &
-&^ thing thing... &
-&~ thing thing... &
- Convenience syntax for prefixing multiple filenames.
- Introduced by & followed by lwsp where lc could go.
- Each lwsp-separated non-ws word is prefixed by &/ etc.
- etc. respectively. No other & escapes are recognised.
- This processing continues until & preceded by lwsp,
- or until EOL (the end of the line), or \ then EOL.
-
-&:<directive> <args>....
- recognised at start of line only (possibly after lwsp)
-
-&:include filename filename should usually be [&]foo.sd.mk
-&:-include filename tolerate nonexistent file
- filenames are relative to $(top_srcdir)
- RHS is &-expanded
-
-&!<lwsp> disables & until EOL (and then disappears)
-
-&# delete everything to end of line
- (useful if the RHS contains unrecognised & constructions)
-
-&:changequote NEWQUOTE
- changes the escape sequence from & to literally NEWQUOTE
- NEWQUOTE may be any series of of non-whitespace characters,
- and is terminated by EOL or lwsp. The whole line is
- discarded.
-
- After this, write NEWQUOTE 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
- NEWQUOTENEWQUOTE => NEWQUOTENEWQUOTE
- NEWQUOTE\NEWQUOTE => NEWQUOTE
- NEWQUOTE\$ => $
- NEWQUOTE:changequote & set escape back to &
-
-&TARGETS_things
- Handled specially. If mentioned at the start of a line
- (possibly following whitespace), declares that this
- subdir ought to have a target `things'. 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 doing so
- 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, is not magic. To make the target exist
- without providing any prerequisites for it, write a line
- containing just `&TARGETS_things +='.
-
- `all' is extra special: every directory has an `all'
- target, which corresponds to &TARGETS.
-
-
-Dollar doubling and macro assistance
-------------------------------------
-
-&$+ Starts dollar-doubling
-&$- Stops dollar-doubling
- Both are idempotent and local to the file or context.
-
-Sometimes we will show $'s being doubled inside another construct.
-This means the content of the construct is $-doubled: $-doubling is
-locally enabled, and restored afterwards.
-
-&:macro NAME => define NAME
-STUFF $ THINGS .. STUFF $$ THINGS
-&:endm .. endef
- NAME is processed for &
-
-&${..$..} => ${eval ${call ..$$..}}
- (matches { } pairs to find the end)
- content is $-doubled (unless it contains $- to turn that off)
-
- Together &:macro and &${...} provide a more reasonable macro
- facility than raw make. They solve the problem that make
- expansions cannot directly generate multiple rules, variable,
- etc.; instead, `$(eval )' must be used, but that re-expands
- the argument, meaning that all the literal text must be
- $-doubled. This applies to the macro text and to the
- arguments. Also `$(eval $(call ...))' is an unfortunate syntax.
- Hence &:macro and &${...}.
-
-While dollar-doubling:
-- - - - - - - - - - -
-
-$ => $$ including $'s produced by other
- &-expansions not mentioned here
-
-&\$ => $
-&$NN => $(NN) where N are digits
-&$( => $(
-
+Warnings
+--------
+
+subdirmk's `generate' program, which does the acual &-substitution,
+can produce some warnings about your .sd.mk files. These can be
+suppressed with the &:warn directive. The warning tags are:
+
+ local+global
+ The same VARNAME was used both with and without an & prefix.
+ This can be confusing. Also, if you avoid this then you will
+ get a warning iff you accidentally leave off a needed &.
+ (You can suppress this warning for a particular VARNAME with
+ the &:local+global directive.)
+
+ single-char-var
+ A variable expansion like $FBAR. make's expansion rules
+ interpret this as $(F)BAR. It's normally better to write
+ it this way, at least if the variable expansion is followed
+ by more letters. Note that &$FOO works differently to
+ raw make: it expands to $(sub_dir_FOO).
+
+ unknown-warning
+ &:warn was used to try to enable a warning that this version
+ of subdirmk does not understand. (Note that an attempt to
+ *dis*able an unknown warning is only reported if some other
+ warning was issued which might have been disabled.)
Subdirectory and variable naming
--------------------------------
Use `git-subtree' to merge the subdirmk/ directory. You may find it
useful to symlink the DEVELOPER-CERTIFICATE file (git can store
symlinks as symlinks - just `git add' the link). And you probably
-want to mention the situation in your top-level COPYING.
+want to mention the situation in your top-level COPYING and HACKING.
Symlink autogen.sh into your project toplevel.
stuff to configure.ac, and fix everything up. Leave the existing
$(MAKE) -C for your existing subdirectories alone. Then you can
convert individual subdirectories, or classes of subdirectories, at
-your leisure. (You must be /sure/ that each subdirectory will be
-entered only once at a time, but your existing recursive make descent
-system should already do that or you already have concurrency bugs.)
+your leisure. (You must be /sure/ that each recursive (non-subdirmk)
+subdirectory will be entered only once at a time, but your existing
+recursive make descent system should already do that or you already
+have concurrency bugs.)
Aside from this, be very wary of any invocation of $(MAKE) anywhere.
This is a frequent source of concurrency bugs in recursive make build
~ian / subdirmk.git / blobdiff