X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?p=subdirmk.git;a=blobdiff_plain;f=README;h=518dd087d853308b13e07aab805349714288d26e;hp=96664ecac434164de67224dc2ac0a34e97fd7ee5;hb=d817b49007e60b0e7392f23caf08dc0328eb32de;hpb=f47abe52f80723f201ec529c2617a4e5a2c35f5a diff --git a/README b/README index 96664ec..518dd08 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 @@ -103,6 +105,19 @@ is already provided in subdirmk, for you to reference like this: &:include subdirmk/clean.sd.mk For example you could put that in Perdir.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. + +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 ------------------ @@ -138,32 +153,46 @@ 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 +--------------------------------- + +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, meanings summary: +Path construction &-expansions are built from the following: - In build tree In source tree - This directory just & &, - Top level &. implies absolute &; + Relative paths in... + build source + + This directory & &^ + Top level . &~ -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. +In more detail, with all the various options laid out: - 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 + 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...) - 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 $(abs)/file $(src)/file $(abs_src)/file +(This assumes you have appropriate make variables src, PWD and +abs_src.) Substitution syntax ------------------- @@ -195,49 +224,31 @@ empty string). &/ => sub/dir/ or nothing &=/ => sub/dir or . -&,lc => $(top_srcdir)/sub/dir/lc -&,/ => $(top_srcdir)/sub/dir/ +&^lc => $(top_srcdir)/sub/dir/lc +&^/ => $(top_srcdir)/sub/dir/ -&;lc => $(top_srcdir)/sub/dir/lc -&;/ => $(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)/sub/dir/lc -&@;/ => $(abs_top_srcdir)/sub/dir/ +&~lc => $(top_srcdir)/lc +&~/ => $(top_srcdir)/ In general: - = return subdir without delimiter (not allowed with `,' `;' `@') - , pathname of this subdirectory in source tree - ; pathname of top level of source tree - . pathname of this directory in build tree, implies absolute pathnames - @ absolute pathnames (forbidden with `.', must come first) + = return subdir without delimiter (not allowed with `^' `~') + ^ pathname of this subdirectory in source tree + ~ pathname of top level of source tree + / terminates the escape (needed if next is not lwsp or space) + lwsp starts multi-word processing (see below) So pathname syntax is a subset of: - '&' [ '@' ] [ ',' | ';' | '.' ] [ lc | '/' ] - - To avoid incomprehensible .sd.mk files, some combinations are not - allowed. For example `&@=./' would mean `$(PWD)/sub/dir' but can - be spelled `$(PWD)/&=/', but more normally the trailing / can be - tolerated, so use `&@/'. + '&' [ '^' | '~' ] [ lc | '/' ] && => && for convenience in shell runes \& => & general escaping mechanism & thing thing... & -&. thing thing... & &@. thing thing... & -&, thing thing... & &@, thing thing... & -&; thing thing... & &@; 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 &/ &./ &@./ + 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.