Legal: Add copyright, licence and warranty notice to many files

[subdirmk.git] / README

diff --git a/README b/README
index efd96be277c4c417a04eb4df31d9bd9ca741cee2..3d18dc28294f0f2dfe87062cd8ca4660b3cd2219 100644 (file)
--- a/README
+++ b/README
@@ -88,13 +88,13 @@ empty string).
 
 &=             =>      sub_dir                         or TOP
 
-&^lc           =>      $(top_srcdir)/sub/dir/lc
-&^/            =>      $(top_srcdir)/sub/dir/
-&^.            =>      $(top_srcdir)/sub/dir
+&^lc           =>      ${top_srcdir}/sub/dir/lc
+&^/            =>      ${top_srcdir}/sub/dir/
+&^.            =>      ${top_srcdir}/sub/dir
 
-&~lc           =>      $(top_srcdir)/lc
-&~/            =>      $(top_srcdir)/
-&~.            =>      $(top_srcdir)
+&~lc           =>      ${top_srcdir}/lc
+&~/            =>      ${top_srcdir}/
+&~.            =>      ${top_srcdir}
 
 In general:
     ^   pathname of this subdirectory in source tree
@@ -114,7 +114,7 @@ So pathname syntax is a subset of:
 &\$            =>      $               provided for $-doubling regimes
 &\NEWLINE                              eats the newline and vanishes
 
-&$VARIABLE     =>      $(sub_dir_VARIABLE)     or $(TOP_VARIABLE)
+&$VARIABLE     =>      ${sub_dir_VARIABLE}     or ${TOP_VARIABLE}
        VARIABLE is ASCII starting with a letter and matching \w+
 
 & thing thing... &
@@ -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.
@@ -233,8 +238,8 @@ $   =>      $$      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
@@ -334,7 +339,12 @@ suppressed with the &:warn directive.  The warning tags are:
        interpret this as $(F)BAR.  It's normally better to write
        it this way, at least if the variable expansion is followed
        by more letters.  Note that &$FOO works differently to
-       raw make: it expands to $(sub_dir_FOO).
+       raw make: it expands to ${sub_dir_FOO}.
+
+    broken-var-ref
+        An attempt at variable expansion looking like $&...
+       You probably expected this to mean $(TOP_F)BAR but it
+       expands to $TOP_FBAR which make thinks means $(T)OP_FBAR.
 
     unknown-warning
        &:warn was used to try to enable a warning that this version
@@ -361,8 +371,9 @@ In your configure.ac, say
   m4_include([subdirmk/subdirmk.ac])
   SUBDIRMK_SUBDIRS([...list of subdirectories in relative syntax...])
 
-Write a Dir.sd.mk in each directory.  The toplevel one should
-probably contain:
+Write a Dir.sd.mk in each directory.  See the substitution syntax
+reference, above, and the example/ directory here.  The toplevel
+Dir.sd.mk should probably contain:
 
   include subdirmk/usual.mk
   include subdirmk/regen.mk
@@ -401,7 +412,7 @@ 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