X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=be1ece7c3d09e40d89170e7d0cb919e343f1369b;hp=4da40911ce83909e880874de657b6d4db797992b;hb=cf4ae9ff56d9313777f95d53092412023f806571;hpb=8c6b02849c6918f1deac8e463b24335844d65b86 diff --git a/README b/README index 4da4091..be1ece7 100644 --- a/README +++ b/README @@ -26,7 +26,7 @@ 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. Unqualified filenames are relative to the build toplevel, and all commands all run @@ -36,11 +36,11 @@ However, the sigil & is treated specially. By and large, it refers to `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 (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. @@ -52,7 +52,7 @@ 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 @@ -69,7 +69,7 @@ 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' @@ -83,32 +83,37 @@ 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 Subdir.sd.mk is the first makefile included after the +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 Subdir.sd.mk. +put them near the top of Dir.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 @@ -122,14 +127,14 @@ 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. @@ -141,13 +146,13 @@ 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 @@ -162,7 +167,7 @@ locations: (i) In the build tree, or in the source tree ? - (ii) In (or relative to) the subdirectory to which this Subdir.sd.mk + (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 @@ -249,7 +254,11 @@ So pathname syntax is a subset of: && => && 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... & @@ -263,11 +272,11 @@ 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) @@ -288,10 +297,12 @@ So pathname syntax is a subset of: Notably 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:: $(&TARGETS_things) @@ -305,13 +316,54 @@ So pathname syntax is a subset of: which recursively implies this directory's `things'. Must be spelled exactly &TARGETS_things. &_TARGETS_things, - for example, is not magic. But mentioning &TARGETS_things in - a #-comment *does* work because the & filter does not care - about comments. + for example, is not magic. To make the target exist + without providing any prerequisites for it, write a line + containing just `&TARGETS_things +='. `all' is extra special: every directory has an `all' target, which corresponds to &TARGETS. + +Dollar doubling and macro assistance +------------------------------------ + +&$+ 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 -------------------------------- @@ -342,13 +394,13 @@ 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 @@ -358,7 +410,7 @@ 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