X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=20658ae2adc3087e1f24db87cababc19aaa154b9;hp=6e4ac8e55a150e26e71b3a105e6e7f18ac24a3d3;hb=143bb5d7dfa60aa0549d934a2e9356961d97895a;hpb=abb0c3933bb2092610fb6053c84b5296b8ce5341 diff --git a/README b/README index 6e4ac8e..20658ae 100644 --- a/README +++ b/README @@ -28,15 +28,17 @@ Basic approach The developer is expected to write a makefile fragment, in each relevant subdirectory, called `Subdir.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 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 (for @..@-substitutions) and included by one autogenerated toplevel @@ -81,27 +83,45 @@ 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 Subdir.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 Subdir.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 Subdir.sd.mk. + +The file Final.sd.mk in the toplevel directory is processed and +included after all the other files. + +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)). Global definitions ------------------ @@ -132,42 +152,52 @@ There are two kinds of template files. 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) + 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 recommended directory reference syntaxes ---------------------------------------------------- +Tables of file reference syntaxes +--------------------------------- -Path construction &-expansions, meanings summary: +In a nonrecursive makefile supporting out of tree builds there are +three separate important distinctions between different file +locations: - Relative paths in... Absolute paths in... - build source build source - - This directory & &, &@ &@, - Top level . &; &@. &@; + (i) In the build tree, or in the source tree ? + + (ii) In (or relative to) the subdirectory to which this Subdir.sd.mk + relates, or relative to the project's top level ? + + (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). + +Path construction &-expansions are built from the following: -Adding `@' means "absolute path". (`&.' is not allowed without @ -because just `&./' is a silly way of writing `.'.) `/' 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. + Relative paths in... + build source + + This directory & &^ + Top level . &~ -In more detail, with the various options for what comes next: +In more detail, with all the various options laid out: Recommended Relative paths in... Absolute paths in... - for build source build source + for build source build source - 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 + 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 &@;file - level any file &;/file &@./file &@;/file - several f g h &; f g h &@. f g h &@; f g h - .mk.in file $(src)/file $(abs)/file $(abs_src)/file + 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...) + +(This assumes you have appropriate make variables src, PWD and +abs_src.) Substitution syntax ------------------- @@ -193,42 +223,46 @@ empty string). 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 TOP +&. => sub/dir or . + (This implies that `&./' works roughly like `&/', although + it can produce a needless `./') -&/ => sub/dir/ or nothing -&=/ => sub/dir or . +&= => sub_dir or TOP -&,lc => $(top_srcdir)/sub/dir/lc &,/ => $(top_srcdir)/sub/dir/ -&;lc => $(top_srcdir)/lc &;/ => $(top_srcdir)/ +&^lc => $(top_srcdir)/sub/dir/lc +&^/ => $(top_srcdir)/sub/dir/ +&^. => $(top_srcdir)/sub/dir -&@lc => $(PWD)/sub/dir/lc &@/ => $(PWD)/sub/dir/ -&@.lc => $(PWD)/lc &@./ => $(PWD)/ -&@,lc => $(abs_top_srcdir)/sub/dir/lc &@,/ => $(abs_top_srcdir)/sub/dir/ -&@;lc => $(abs_top_srcdir)/lc &@;/ => $(abs_top_srcdir)/ +&~lc => $(top_srcdir)/lc +&~/ => $(top_srcdir)/ +&~. => $(top_srcdir) In general: - = return subdir without delimiter (not allowed with `,' `;' `@') - , pathname of this subdirectory in source tree - ; pathname of top level of source tree - . pathname of this directory in build tree, `@' must be specified - @ absolute pathnames + ^ 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 | '/' ] - - To avoid incomprehensible .sd.mk files, some combinations are not - allowed. For example `&=./' would mean `.' and `&./' would be the - empty string. Variations with `=' and one of `@' `,' `;' are - uncommon and must be written using make variables instead. + '&' [ '^' | '~' ] [ lc | '/' | '.' | '=' ] && => && for convenience in shell runes -\& => & general escaping mechanism -& thing thing... & &@ thing thing... & - &. thing thing... & -&, thing thing... & &@, thing thing... & -&; thing thing... & &@; thing thing... & +&\& => & 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. @@ -238,35 +272,37 @@ So pathname syntax is a subset of: &: .... recognised at start of line only (possibly after lwsp) - args are processed for & -&:include filename filename should usually be foo.sd.mk +&:include filename filename should usually be [&]foo.sd.mk &:-include filename tolerate nonexistent file filenames are relative to $(top_srcdir) + RHS is &-expanded &! 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. +&: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 STUFF instead of &, everywhere. + 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 - STUFFSTUFF => STUFFSTUFF - \STUFF => STUFF - STUFF!& set escape back to & + NEWQUOTENEWQUOTE => NEWQUOTENEWQUOTE + NEWQUOTE\NEWQUOTE => NEWQUOTE + NEWQUOTE\$ => $ + NEWQUOTE:changequote & set escape back to & &TARGETS_things - Handled specially. If mentioned, declares that this + 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:: $(&TARGETS_things) @@ -280,13 +316,54 @@ So pathname syntax is a subset of: which recursively implies this directory's `things'. Must be spelled exactly &TARGETS_things. &_TARGETS_things, - for example, is not magic. But mentioning &TARGETS_things in - a #-comment *does* work because the & filter does not care - about comments. + for example, is not magic. To make the target exist + without providing any prerequisites for it, write a line + containing just `&TARGETS_things +='. `all' is extra special: every directory has an `all' target, which corresponds to &TARGETS. + +Dollar doubling and macro assistance +------------------------------------ + +&$+ 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 => $(NN) where N are digits +&$( => $( + + Subdirectory and variable naming -------------------------------- @@ -323,7 +400,7 @@ 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 @@ -354,6 +431,13 @@ 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 -----------------