Error handling: Better reporting of nest-related errors

[subdirmk.git] / README

diff --git a/README b/README
index e3259c0924414e19770c5fa42007646696ddbdab..20658ae2adc3087e1f24db87cababc19aaa154b9 100644 (file)
--- a/README
+++ b/README
@@ -83,17 +83,18 @@ targets may be in run in parallel: there is only one `make' invocation
 at a time.  There is no sequencing between subdirectories, only been
 individual targets (as specified according to their dependencies).
 
-You can define other per-directory recursive targets too: simply
-mention (usually, by setting) the variable &TARGETS_zonk, or whatever.
-This will create a src/zonk target (for appropriate value of src/).
-Unlike `all', these other targets only exist in areas of the project
-where at least something mentions them.  So for example, if
-&TARGETS_zonk is mentioned in src but not lib, `make zonk' in
-lib will fail.  If you want to make a target exist everywhere,
-mention its name in Prefix.sd.mk or Suffix.sd.mk (see below).
-
-Prefix.sd.mk, Suffix.sd.mk, inclusion
--------------------------------------
+You can define other per-directory recursive targets too: set the
+variable &TARGETS_zonk, or whatever (being sure to write &TARGETS_zonk
+at the start of a line).  This will create a src/zonk target (for
+appropriate value of src/).  Unlike `all', these other targets only
+exist in areas of the project where at least something mentions them.
+So for example, if &TARGETS_zonk is set in src but not lib, `make
+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, 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
@@ -111,6 +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
@@ -148,7 +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
@@ -250,7 +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)
@@ -319,6 +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
 --------------------------------