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
automatic regeneration for all of this template substitution, and for
config.status etc. is done for you.
-Summary of 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:
- In build tree In source tree
- This directory just & &,
- Top level &. implies absolute &;
+ (i) In the build tree, or in the source tree ?
-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.
+ (ii) In (or relative to) the subdirectory to which this Subdir.sd.mk
+ relates, or relative to the project's top level ?
- 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
+ (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).
- Top lc &.file &;file &@;file
- level any file &./file &;/file &@;/file
- .mk.in file $(abs)/file $(src)/file $(abs_src)/file
- several f g h &. f g h &; f g h &@; f g h
- &@. file
- &@. f g h
+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
-------------------
variables usually uppercase. Otherwise, use another syntax:
&_ => sub_dir_ or TOP_
-&/ => sub/dir/ or nothing
&=_ => sub_dir or TOP
+
+&/ => sub/dir/ or nothing
&=/ => sub/dir or .
-&^ => $(top_srcdir)/sub/dir or $(top_srcdir)
-&~ => $(abs_top_srcdir)/sub/dir or $(abs_top_srcdir)
+
+&,lc => $(top_srcdir)/sub/dir/lc
+&,/ => $(top_srcdir)/sub/dir/
+
+&;lc => $(top_srcdir)/lc
+&;/ => $(top_srcdir)/
In general:
- ^ filenames in source tree rather than build tree
- ~ filenames are absolute rather than relative
- @ filenames do not contain subdir (useful with the above)
+ = 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 | '/' ]
&& => && for convenience in shell runes
\& => & general escaping mechanism
& thing thing... &
-& ^ thing thing... &
-& ~ thing thing... &
+&, thing thing... &
+&; thing thing... &
Convenience syntax for prefixing multiple filenames.
- Introduced by & followed by lwsp (space or tab).
- Each lwsp-separated non-ws word is prefixed by &/ &^/ &~/
- respectively. No other & escapes are recognised.
+ Introduced by & followed by lwsp where lc could go.
+ 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.
~ian / subdirmk.git / blobdiff