X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=50bd4d3261898d8d96ff03bed8d6774212051f84;hp=0b95b98ff17f75152a7279503bc8139c56f86471;hb=c4859585c93ccf44d33e657dec83eec9cfde0ab6;hpb=ea45444f2cdeb2543e25b53f760c89dbf060f87c diff --git a/README b/README index 0b95b98..50bd4d3 100644 --- a/README +++ b/README @@ -20,25 +20,27 @@ style is not very ergonomic. The main difficulties are: `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 -------------- The developer is expected to write a makefile fragment, in each -relevant subdirectory, called `Subdir.sd.mk'. +relevant subdirectory, called `Dir.sd.mk'. -These fragments may contain ordinary make language. +These fragments may contain ordinary make language. Unqualified +filenames are relative to the build toplevel, and all commands all run +there. However, the sigil & is treated specially. By and large, it refers to -`the current directory'. There are a variety of convenient -constructions. +`the build directory corresponding to this .sd.mk file', etc. +There are a variety of convenient constructions. -The result is that to a large extent, the Subdir.sd.mk has an easy way +The result is that to a large extent, the Dir.sd.mk has an easy way to namespace its "local" make variables, and an easy way to refer to -its "local" filenames. +its "local" filenames (and filenames in general). -The Subdir.sd.mk's are filtered, fed through autoconf in the usual way +The Dir.sd.mk's are filtered, fed through autoconf in the usual way (for @..@-substitutions) and included by one autogenerated toplevel makefile. @@ -50,9 +52,195 @@ Each subdirectory is also provided with an autogenerated `Makefile' which exists purely to capture ordinary make invocations and arrange for something suitable to happen. -Where there are dependencies between subdirectories, each Subdir.sd.mk +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 $(TOP_VARIABLE) + VARIABLE is ASCII starting with a letter and matching \w+ + +& thing thing... & +&^ thing thing... & +&~ thing thing... & + Convenience syntax for prefixing multiple filenames. + Introduced by & followed by lwsp where lc could go. + Each lwsp-separated non-ws word is prefixed by &/ etc. + etc. respectively. No other & escapes are recognised. + This processing continues until & preceded by lwsp, + or until EOL (the end of the line), or \ then EOL. + +&: .... + recognised at start of line only (possibly after lwsp) + +&:include filename filename should usually be [&]foo.sd.mk +&:-include filename tolerate nonexistent file + RHS is &-expanded but filenames are relative to the top + srcdir. This implies that unqualified names are like &~/ + whereas &/ is like &^/. &^ and &~ do not work here because + they expand to constructions involving literally + `$(top_srcdir)', but the RHS is not make-expanded. + +&! 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 --------------------------------------------- @@ -67,7 +255,7 @@ 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. &TARGETS is magic in this way. (In -src/Subdir.sd.mk, &TARGETS of course refers to a make variable called +src/Dir.sd.mk, &TARGETS of course refers to a make variable called src_TARGETS.) The `all' target in a parent directory is taken to imply the `all' @@ -81,40 +269,91 @@ targets may be in run in parallel: there is only one `make' invocation at a time. There is no sequencing between subdirectories, only been individual targets (as specified according to their dependencies). -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 (for appropriate value of src/). -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 -lib will fail. If you want to make a target exist everywhere, -mention its name in Perdir.sd.mk (see below). +You can define other per-directory recursive targets too: set the +variable &TARGETS_zonk, or whatever (being sure to write &TARGETS_zonk +at the start of a line). This will create a src/zonk target (for +appropriate value of src/). 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 set in src but not lib, `make +zonk' in lib will fail. If you want to make a target exist +everywhere, += it with nothing in Prefix.sd.mk or Suffix.sd.mk (see +below). -Perdir.sd.mk, inclusion ------------------------ +Prefix.sd.mk, Suffix.sd.mk, Final.sd.mk, inclusion +-------------------------------------------------- -The file Perdir.sd.mk in the toplevel of the source is automatically -processed after each individual directory's Subdir.sd.mk, and the -&-substituted contents therefore appear once for each subdirectory. +The files Prefix.sd.mk and Suffix.sd.mk in the toplevel of the source +are automatically processed before and after each individual +directory's Dir.sd.mk, and the &-substituted contents therefore +appear once for each subdirectory. This lets you do per-directory boilerplate. Some useful boilerplate is already provided in subdirmk, for you to reference like this: &:include subdirmk/cdeps.sd.mk &:include subdirmk/clean.sd.mk -For example you could put that in Perdir.sd.mk. +For example you could put that in Suffix.sd.mk. + +The top-level Dir.sd.mk is the first makefile included after the +autogenerated `main.mk' which merely has some basic settings and +includes. So if you want to get in early and set global variables, +put them near the top of Dir.sd.mk. + +The file Final.sd.mk in the toplevel directory is processed and +the result included after all the other files. Its subdirmk +filtering context inherits warning suppressions from the toplevel's +Dir.sd.mk etc., but not anything else. + +subdirmk's filter script itself sets (only) these variables: + top_srcdir + abs_top_srcdir + SUBDIRMK_MAKEFILES + MAKEFILE_TEMPLATES +You are likely to want to define $(PWD), and shorter names for +top_srdir and abs_top_srcdir (we suggest $(src) and $(abs_src)). + +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 &. + The generation of this warning depends on scanning your + makefile for things that look like variable references, which + subdirmk does not do completely perfectly. Exciting make + syntax may evade this warning, or require suppressions. + (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.) 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 +once. You can put them in your top-level Dir.sd.mk, or a separate file you `include' and declare using SUBDIRMK_MAKEFILES. If you need different settings of variables like CC for different subdirectories, you should probably do that with target-specific variable settings. See the info node `(make) Target-specific'. -Subdirectory templates `.sd.mk' vs plain autoconf templates `.mk.in' +Directory templates `.sd.mk' vs plain autoconf templates `.mk.in' -------------------------------------------------------------------- There are two kinds of template files. @@ -126,146 +365,60 @@ There are two kinds of template files. Instantiated Usu. once per subdir Once only - Need to be mentioned No, but Subdir.sd.mk All not in subdirmk/ + Need to be mentioned No, but Dir.sd.mk All not in subdirmk/ 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 - (but not needed for Subdir.sd.mk - Subdir and Perdir) + (but not needed for Dir.sd.mk + Prefix, Suffix, Final) If you `include subdirmk/regen.mk', dependency management and automatic regeneration for all of this template substitution, and for config.status etc. is done for you. -Summary of directory reference syntaxes ---------------------------------------- -Path construction &-expansions, meanings summary: +Tables of file reference syntaxes +--------------------------------- - In build tree In source tree - This directory just & &, - Top level &. implies absolute &; +In a nonrecursive makefile supporting out of tree builds there are +three separate important distinctions between different file +locations: -Adding `@' means "absolute path". This is not needed with &. because -there is never any need to use &. since it would expand to nothing. -`/' terminates the escape (needed if the next thing is not a lowercase -character, or space). `=' means "just the value, no /". Space starts -multi-word processing. + (i) In the build tree, or in the source tree ? - Recommended In build tree In source tree - when Relative Absolute Relative Absolute - - This lc &file &@file &,file &@,file - directory any &/file &@/file &,/file &@,/file - several & f g h &@ f g h &, f g h &^, f g h + (ii) In (or relative to) the subdirectory to which this Dir.sd.mk + relates, or relative to the project's top level ? - Top lc &.file &;file &@;file - level any file &./file &;/file &@;/file - .mk.in file $(abs)/file $(src)/file $(abs_src)/file - several f g h &. f g h &; f g h &@; f g h - &@. file - &@. f g h + (iii) Absolute or relative pathname ? Usually relative pathnames + suffice. Where an absolute pathname is needed, it can be built + out of &/ and an appropriate make variable such as $(PWD). -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. +Path construction &-expansions are built from the following: -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). + Relative paths in... + build source + + This directory & &^ + Top level . &~ -&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: +In more detail, with all the various options laid out: -&_ => 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) + Recommended Relative paths in... Absolute paths in... + for build source build source + + This lc &file &^file $(PWD)/&file $(abs_src)/&file + directory any &/file &^/file $(PWD)/&/file $(abs_src)/&/file + several & f g h &^ f g h $(addprefix...) + + Top lc file &~file + level any file &~/file $(PWD)/file $(abs_src)/file + .mk.in file $(src)/file $(PWD)/file $(abs_src)/file + several f g h &~ f g h $(addprefix...) -In general: - ^ filenames in source tree rather than build tree - ~ filenames are absolute rather than relative - @ filenames do not contain subdir (useful with the above) +(This assumes you have appropriate make variables src, PWD and +abs_src.) -&& => && 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 & preceded by lwsp, - or until EOL (the end of the line), or \ then EOL. - -&: .... - 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 - filenames are relative to $(top_srcdir) - -&! disables & until EOL (and then disappears) - -&# delete everything to end of line - (useful if the RHS contains unrecognised & constructions) - -&!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 - are 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 => STUFFSTUFF - \STUFF => STUFF - STUFF!& set escape back to & - -&TARGETS_things - Handled specially. If mentioned, 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. But mentioning &TARGETS_things 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 -------------------------------- @@ -288,7 +441,7 @@ Incorporating this into your project 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. @@ -297,13 +450,13 @@ In your configure.ac, say m4_include([subdirmk/subdirmk.ac]) SUBDIRMK_SUBDIRS([...list of subdirectories in relative syntax...]) -Write a Subdir.sd.mk in each directory. The toplevel one should +Write a Dir.sd.mk in each directory. The toplevel one should probably contain: include subdirmk/usual.mk include subdirmk/regen.mk -Write a Perdir.sd.mk in the toplevel, if you want. It should probably +Write a Suffix.sd.mk in the toplevel, if you want. It should probably have: &:include subdirmk/cdeps.sd.mk @@ -313,13 +466,14 @@ Hints ----- You can convert your project incrementally. Start with the top-level -Makefile.in and rename it to Subdir.sd.mk, and add the appropriate +Makefile.in and rename it to Dir.sd.mk, and add the appropriate 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 @@ -334,6 +488,13 @@ makefiles, you may find that just `make' is broken now and cannot get far enough to regenerate a working set of makefiles. If this happens just rerun ./config.status by hand. +If you go back and forth between different versions of your code you +can sometimes find that `make' complains that one of your Subdir.sd.mk +files is missing: typically, if iot was used and therefore a +dependency in some other version of your code. If you run `make +clean' (or `make realclean') these dependencies are suppressed, which +will clear up the problem. + Legal information -----------------