From 66697360832da018ea0423dda32024a8819f294b Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?John=20Ankarstr=C3=B6m?= <john@ankarstrom.se>
Date: Sun, 24 Jul 2022 21:11:09 +0200
Subject: Improve makedeps.

This version correctly finds dependencies inside dependencies.

One may wonder why I don't just use gcc -MM c/*.cpp, which produces
basically the same result. The simple reason is that gcc does it very
slowly. It would be unfeasible to run before every compilation.
---
 makedeps | 58 ++++++++++++++++++++++++++++++++++++++++++++++------------
 1 file changed, 46 insertions(+), 12 deletions(-)

diff --git a/makedeps b/makedeps
index 829d389..70589ca 100644
--- a/makedeps
+++ b/makedeps
@@ -1,24 +1,58 @@
 #!/usr/bin/env perl
 
-use strict;
+use v5.12;
 use warnings;
+use subs qw/for_includes/;
 
 open my $fh, ">", "deps.mk";
 print $fh "# This file is generated by makedeps.\n";
+
 while (my $f = glob("c/*.cpp")) {
-	open my $gh, "<", $f;
 	$f =~ s,^c/,,;
 	$f =~ s/\.cpp$//;
-	if ($f eq "main") {
-		print $fh "b/\$(EXE):";
-	} else {
-		print $fh "b/$f.obj:";
+
+	if ($f eq "main") { print $fh "b/\$(EXE):"; }
+	else { print $fh "b/$f.obj:"; }
+
+	# Print dependencies in source file.
+	my @deps;
+	for_includes "c/$f.cpp", sub {
+		my $f = shift;
+		return if grep { $_ eq $f } @deps;
+		push @deps, $f;
+		print $fh " c/$f";
+
+		# Print dependencies in dependency.
+		for_includes "c/$f", sub {
+			my $f = shift;
+			return if grep { $_ eq $f } @deps;
+			push @deps, $f;
+			print $fh " c/$f";
+		}
+	};
+
+	print $fh "\n";
+}
+
+sub for_includes ($&) {
+	my $f = shift;
+	my $c = shift;
+	state %cache;
+
+	# Retrieve dependencies from cache.
+	if (exists $cache{$f}) {
+		$c->($_) for @{$cache{$f}};
 	}
-	while ($_ = <$gh>) {
-		next if /^$/;
-		goto n if not /#/;
-		print $fh " c/$1" if /^#include\s*"([^"]+)"/;
+
+	# Find dependencies in file.
+	else {
+		open my $gh, "<", $f or die "($f) $!";
+		while ($_ = <$gh>) {
+			next if /^$/;
+			last if not /#/;
+			next if not /^#include\s*"([^"]+)"/;
+			push @{$cache{$f}}, $1;
+			$c->($1);
+		}
 	}
-      n:
-	print $fh "\n";
 }
-- 
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