X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=bea3c1b5ed053caaeb8078f821361add0778a0da;hp=b4f9a1563d21b6277056ed6bc1cb93fc3a00cce8;hb=8a588ad0cc1d3e2944bb29fb3ce19ac2d0dbdcc4;hpb=e7d6ffdaf26c91a05670954a3d84ed5fd9ea69b8 diff --git a/README b/README index b4f9a15..bea3c1b 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. @@ -50,131 +52,16 @@ 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. -Invocation, "recursive" per-directory targets ---------------------------------------------- - -Arrangements are made so that when you run `make foo' in a -subdirectory, it is like running the whole toplevel makefile, from the -toplevel, as `make subdir/foo'. If `subdir/foo' is a file that might -be built, that builds it. - -But `foo' can also be a conventional target like `all'. - -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_TARGETS.) - -The `all' target in a parent directory is taken to imply the `all' -targets in all of its subdirectories, recursively. And in the -autogenerated stub Makefiles, `all' is the default target. So if you -just type `make' in the toplevel, you are asking for `&all' -(/all) for every directory in the project. - -In a parallel build, the rules for all these various subdirectory -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). - -Perdir.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. - -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. - -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. - -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' --------------------------------------------------------------------- - -There are two kinds of template files. - - Filename .sd.mk .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 - - 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) - -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 ---------------------------------------------------- - -Path construction &-expansions, meanings summary: - - Relative paths in... Absolute paths in... - build source build source - - This directory & &, &@ &@, - Top level . &; &@. &@; - -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. - -In more detail, with the various options for what comes next: - - Recommended Relative paths in... Absolute paths in... - 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 - - Top lc file &;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 - 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. +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, @@ -193,42 +80,46 @@ 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 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 | '/' ] - - 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 +129,27 @@ 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 +&: => &: + for make multiple targets syntax + recognised anywhere *except* start of line + +&:include filename filename should usually be [&]foo.sd.mk &:-include filename tolerate nonexistent file - filenames are relative to $(top_srcdir) + RHS is &-expanded but filenames are relative to the top + srcdir. This implies that unqualified names are like &~/ + whereas &/ is like &^/. &^ and &~ do not work here because + they expand to constructions involving literally + `$(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) -&!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 + 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) @@ -280,27 +163,218 @@ 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. -Subdirectory and variable naming --------------------------------- +Directives +- - - - - + +&: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 any warnings relating to forthcoming mentions + to VARIABLE or &VARIABLE, as applicable. Scope ends at + the end of the current directory's Suffix.sd.mk. + Prefixing with ! removes [&]VARIABLE from the suppresion list. + +&: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. -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. + Notably + NEWQUOTENEWQUOTE => NEWQUOTENEWQUOTE + NEWQUOTE\NEWQUOTE => NEWQUOTE + NEWQUOTE\$ => $ + NEWQUOTE:changequote & set escape back to & -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. +Dollar doubling and macro assistance +------------------------------------ + +&$+ Starts dollar-doubling +&$- Stops dollar-doubling + Both are idempotent and local to the file or context. + +This is useful both for make macrology involving $(eval ...), and +possibly for helping write complicated recipes involving shell +variables, inline Perl code, etc. + +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) + cf &(...), see "Convenience syntax for eval", below. + +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.) + +Convenience syntax for eval +- - - - - - - - - - - - - - + +&(thing => $(call thing +&( thing => $(call thing + and specially: +&(&lc => $(call sub_dir_lc or $(call TOP_lc +&( &lc => $(call sub_dir_lc or $(call TOP_lc + even though lc would normally be thought a filename + +Unlike &{...}, this does not involve any dollar-doubling. + + +Invocation, "recursive" per-directory targets +--------------------------------------------- + +Arrangements are made so that when you run `make foo' in a +subdirectory, it is like running the whole toplevel makefile, from the +toplevel, as `make subdir/foo'. If `subdir/foo' is a file that might +be built, that builds it. + +But `foo' can also be a conventional target like `all'. + +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/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' +targets in all of its subdirectories, recursively. And in the +autogenerated stub Makefiles, `all' is the default target. So if you +just type `make' in the toplevel, you are asking for `&all' +(/all) for every directory in the project. + +In a parallel build, the rules for all these various subdirectory +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: 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). + +Prefix.sd.mk, Suffix.sd.mk, Final.sd.mk, inclusion +-------------------------------------------------- + +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 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}. + + broken-var-ref + An attempt at variable expansion looking like $&... + You probably expected this to mean $(TOP_F)BAR but it + expands to $TOP_FBAR which make thinks means $(T)OP_FBAR. + + 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.) + + +Guides, hints, and further explanations +======================================= Incorporating this into your project ------------------------------------ @@ -308,7 +382,7 @@ 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. @@ -317,29 +391,32 @@ 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 -probably contain: +Write a Dir.sd.mk in each directory. See the substitution syntax +reference, above, and the example/ directory here. The toplevel +Dir.sd.mk 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 &:include subdirmk/clean.sd.mk + 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 @@ -354,9 +431,111 @@ 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 Dir.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. + + +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 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'. + + +Directory templates `.sd.mk' vs plain autoconf templates `.mk.in' +-------------------------------------------------------------------- + +There are two kinds of template files. + + Filename .sd.mk .mk.in + + Processed by &-substitution, autoconf only + then autoconf + + Instantiated Usu. once per subdir Once only + + 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 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. + + +Tables of file reference syntaxes +--------------------------------- + +In a nonrecursive makefile supporting out of tree builds there are +three separate important distinctions between different file +locations: + + (i) In the build tree, or in the source tree ? + + (ii) In (or relative to) the subdirectory to which this Dir.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: + + Relative paths in... + build source + + This directory & &^ + Top level . &~ + +In more detail, with all the various options laid out: + + 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...) + +(This assumes you have appropriate make variables src, PWD and +abs_src.) + + +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. + Legal information ------------------ +================= subdirmk is Copyright 2019 Mark Wooding