`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
--------------
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.)
-
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,
^ 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
&: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.
&!<lwsp> disables & until EOL (and then disappears)
discarded.
After this, write NEWQUOTE instead of &, everywhere.
- The effect is global and lasts until the next setting.
+ 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.
&$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.)
Subdirectory and variable naming
--------------------------------
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.
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
~ian / subdirmk.git / blobdiff