Syntax: Provide convenience syntax &( for $(eval

[subdirmk.git] / README

diff --git a/README b/README
index 0b84a0ec35dcfd6aec0c08736bd3f9b028b25b91..d85a68804c4e4bf8adff2480fc37fcf9bcef0ed7 100644 (file)
--- a/README
+++ b/README
@@ -174,10 +174,11 @@ So pathname syntax is a subset of:
        by the final warning state after processing all the toplevel
        input files (including Final.sd.mk).
 
-&:local+global [&]VARIABLE ...
-       Suppresses the warning about seeing both VARIABLE and
-       &VARIABLE.  Any & specified in the RHS is redundant: this
-       always affects both versions identically.
+&:local+global [!][&]VARIABLE ...
+       Suppresses any warnings relating to forthcoming mentions
+       to VARIABLE or &VARIABLE, as applicable.  Scope ends at
+       the end of the current directory's Suffix.sd.mk.
+       Prefixing with ! removes [&]VARIABLE from the suppresion list.
 
 &:changequote NEWQUOTE
        changes the escape sequence from & to literally NEWQUOTE
@@ -205,6 +206,10 @@ Dollar doubling and macro assistance
 &$-            Stops dollar-doubling
        Both are idempotent and local to the file or context.
 
+This is useful both for make macrology involving $(eval ...), and
+possibly for helping write complicated recipes involving shell
+variables, inline Perl code, etc.
+
 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.
@@ -214,9 +219,10 @@ STUFF $ THINGS     ..      STUFF $$ THINGS
 &:endm         ..      endef
        NAME is processed for &
 
-&${..$..} =>   ${eval ${call ..$$..}}
+&{..$..}       =>      ${eval ${call ..$$..}}
        (matches { } pairs to find the end)
        content is $-doubled (unless it contains &$- to turn that off)
+       cf &(...), see "Convenience syntax for eval", below.
 
 Together &:macro and &${...} provide a more reasonable macro facility
 than raw make.  They solve the problem that make expansions cannot
@@ -233,13 +239,25 @@ $ =>      $$      including $'s produced by other
                         &-expansions not mentioned here
 
 &\$    =>      $
-&$(    =>      $(
-&$NN   =>      $(NN)   where N are digits
+&$(    =>      ${      (expands to { } so it is useable for shell too)
+&$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.)
 
+Convenience syntax for eval
+- - - - - - - - - - - - - -
+
+&(thing                =>      $(call thing
+&( thing       =>      $(call thing
+       and specially:
+&(&lc          =>      $(call sub_dir_lc       or $(call TOP_lc
+&( &lc         =>      $(call sub_dir_lc       or $(call TOP_lc
+       even though lc would normally be thought a filename
+
+Unlike &{...}, this does not involve any dollar-doubling.
+
 
 Invocation, "recursive" per-directory targets
 ---------------------------------------------
@@ -407,7 +425,7 @@ far enough to regenerate a working set of makefiles.  If this happens
 just rerun ./config.status by hand.
 
 If you go back and forth between different versions of your code you
-can sometimes find that `make' complains that one of your Subdir.sd.mk
+can sometimes find that `make' complains that one of your Dir.sd.mk
 files is missing: typically, if iot was used and therefore a
 dependency in some other version of your code.  If you run `make
 clean' (or `make realclean') these dependencies are suppressed, which