From 3177fb7abb48479332cce56b02b6407968fb2d27 Mon Sep 17 00:00:00 2001
From: Ian Jackson <ijackson@chiark.greenend.org.uk>
Date: Sat, 28 Dec 2019 00:36:50 +0000
Subject: [PATCH] Macro assistance part 1 - macro directive

Define the &:macro directive, which is a dollar-doubled version of
make's own `define'.

We must introuce a new concept of `nesting', for when "the content of
the construct is $-doubled" in the words of the README.  The
implementation is in the main process_input_mk function: it is a
multi-line scope of some kind with an ad-hoc ending condition, and its
own dollar-doubling setting.

We will also want a convenient syntax for $(eval $(call...)), which
we're going to introduce in a moment.

Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
---
 README                       |  9 +++++++++
 generate                     | 21 ++++++++++++++++++++-
 tests/filter/extract-doctest |  2 ++
 3 files changed, 31 insertions(+), 1 deletion(-)

diff --git a/README b/README
index d750cb8..130a1c7 100644
--- a/README
+++ b/README
@@ -331,6 +331,15 @@ Dollar doubling and macro assistance
 &$-		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 &
+
 While dollar-doubling:
 - - - - - - - - - - -
 
diff --git a/generate b/generate
index ec47866..3ccfa0d 100755
--- a/generate
+++ b/generate
@@ -180,13 +180,29 @@ sub process_input_mk ($$$$) {
     $pfxmap{$_} = $srcdirmap{$_}.'/' foreach keys %srcdirmap;
 
     local $ddbl;
+    my @nest;
+
+    my $push_nest = sub {
+	my ($nk, $nndbl) = @_;
+	unshift @nest, [ $nk, $ddbl ];
+	$ddbl = $nndbl;
+    };
+    my $pop_nest = sub {
+	my ($nk) = @_;
+	die unless $nest[0][0] eq $nk;
+	$ddbl = (shift @nest)[1];
+    };
 
     while (<$input>) {
 	if (s#^\s*$esc\:changequote\s+(\S+)\s+$##) {
 	    $$esclitr = $1;
 	    $set_esc->();
 	    next;
-	} elsif (s#^\s*$esc\:(?=(-?)include)##) {
+	} elsif (s#^\s*$esc\:endm\s+$##) {
+	    $pop_nest->('Macro');
+	    od "endef\n";
+	    next;
+	} elsif (s#^\s*$esc\:(?=(-?)include|macro)##) {
 	    $buffering_output='';
 	} elsif (m#^\s*$esc\:([a-z][-0-9a-z_]*)#) {
 	    die "unknown directive $1";
@@ -238,6 +254,9 @@ sub process_input_mk ($$$$) {
 		my $subf = "$srcdir/$2";
 		process_input_mk($targets, $subf, $esclitr, $1);
 		od "\n";
+	    } elsif (m#^macro\s+(\S+)\s+$#) {
+		od "define $1\n";
+		$push_nest->('Macro', 1);
 	    } else {
 		die "internal error buffering directive $_ ";
 	    }
diff --git a/tests/filter/extract-doctest b/tests/filter/extract-doctest
index 35870ce..57f5313 100755
--- a/tests/filter/extract-doctest
+++ b/tests/filter/extract-doctest
@@ -138,6 +138,8 @@ sub writeout ($) {
 		  'dollar doubling',
 		  sub {
 		      my ($e) = @_;
+		      # adhoc: skip &:macro in already-doubling part
+		      return 0 if $e->{In} =~ m{^\&\:macro};
 		      return 0 if $e->{CQ};
 		      return $e->{DD} || !grep {
 			  # If there are two entries with the same In,
-- 
2.30.2