X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=41110ce410ac8ca098cff5e28cbd182951fcc4ee;hp=20658ae2adc3087e1f24db87cababc19aaa154b9;hb=d1f413fb1910af153ed54281decab1696c7357b3;hpb=8c3e6dc4a16406496aa6991f8dc2fb77a96359ea diff --git a/README b/README index 20658ae..41110ce 100644 --- a/README +++ b/README @@ -20,13 +20,13 @@ 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. 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' @@ -98,7 +98,7 @@ 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 Subdir.sd.mk, and the &-substituted contents therefore +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 @@ -107,10 +107,10 @@ is already provided in subdirmk, for you to reference like this: &:include subdirmk/clean.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. @@ -127,14 +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. @@ -146,65 +146,25 @@ 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 + (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 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: - - 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.) - 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, @@ -243,13 +203,13 @@ 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 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 | '/' | '.' | '=' ] + '&' [ '^' | '~' ] [ lc | '/' | '.' ] && => && for convenience in shell runes @@ -275,31 +235,17 @@ So pathname syntax is a subset of: &:include filename filename should usually be [&]foo.sd.mk &:-include filename tolerate nonexistent file - filenames are relative to $(top_srcdir) - RHS is &-expanded + RHS is &-expanded but filenames are relative to the top + srcdir. This implies that unqualified names are like &~/ + whereas &/ is like &^/. &^ and &~ do not work here because + they expand to constructions involving literally + `$(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) -&: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 @@ -323,6 +269,37 @@ So pathname syntax is a subset of: `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 ------------------------------------ @@ -363,6 +340,78 @@ $ => $$ including $'s produced by other &$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.) + + +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.) + +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 -------------------------------- @@ -385,7 +434,7 @@ 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. @@ -394,7 +443,7 @@ 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 @@ -410,13 +459,14 @@ 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