X-Git-Url: https://www.chiark.greenend.org.uk/ucgi/~ian/git?a=blobdiff_plain;f=README;h=20658ae2adc3087e1f24db87cababc19aaa154b9;hb=20e5ccd063565c2207066d4ed3b48be49143194b;hp=5e78187942da813ac76be9ff07b9c9cada4cd232;hpb=fd49f563108abb6cdb9806344be415b656208334;p=subdirmk.git

diff --git a/README b/README
index 5e78187..20658ae 100644
--- a/README
+++ b/README
@@ -93,8 +93,8 @@ 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).
 
-Prefix.sd.mk, Suffix.sd.mk, inclusion
--------------------------------------
+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
@@ -112,6 +112,9 @@ 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.
 
+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
   abs_top_srcdir
@@ -149,7 +152,7 @@ There are two kinds of template files.
  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
-                           Prefix, Suffix)
+                           Prefix, Suffix, Final)
 
 If you `include subdirmk/regen.mk', dependency management and
 automatic regeneration for all of this template substitution, and for
@@ -251,7 +254,7 @@ 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)
@@ -320,6 +323,47 @@ So pathname syntax is a subset of:
 	`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
 --------------------------------