#! /usr/bin/perl
#
# Detect cycles in the header file dependency graph
# Vegard Nossum <[email protected]>
#

use strict;
use warnings;

use Getopt::Long;

my $opt_all;
my @opt_include;
my $opt_graph;

&Getopt::Long::Configure(qw(bundling pass_through));
&GetOptions(
help => \&help,
version => \&version,

all => \$opt_all,
"I=s" => \@opt_include,
graph => \$opt_graph,
);

push @opt_include, 'include';
my %deps = ();
my %linenos = ();

my @headers = grep { strip($_) } @ARGV;

parse_all(@headers);

if($opt_graph) {
graph();
} else {
detect_cycles(@headers);
}


sub help {
print "Usage: $0 [options] file...\n";
print "\n";
print "Options:\n";
print " --all\n";
print " --graph\n";
print "\n";
print " -I includedir\n";
print "\n";
print "To make nice graphs, try:\n";
print " $0 --graph include/linux/kernel.h | dot -Tpng -o graph.png\n";
exit;
}

sub version {
print "headerdep version 2\n";
exit;
}

# Get a file name that is relative to our include paths
sub strip {
my $filename = shift;

for my $i (@opt_include) {
my $stripped = $filename;
$stripped =~ s/^$i\///;

return $stripped if $stripped ne $filename;
}

return $filename;
}

# Search for the file name in the list of include paths
sub search {
my $filename = shift;
return $filename if -f $filename;

for my $i (@opt_include) {
my $path = "$i/$filename";
return $path if -f $path;
}
return;
}

sub parse_all {
# Parse all the headers.
my @queue = @_;
while(@queue) {
my $header = pop @queue;
next if exists $deps{$header};

$deps{$header} = [] unless exists $deps{$header};

my $path = search($header);
next unless $path;

open(my $file, '<', $path) or die($!);
chomp(my @lines = <$file>);
close($file);

for my $i (0 .. $#lines) {
my $line = $lines[$i];
if(my($dep) = ($line =~ m/^#\s*include\s*<(.*?)>/)) {
push @queue, $dep;
push @{$deps{$header}}, [$i + 1, $dep];
}
}
}
}

sub print_cycle {
# $cycle[n] includes $cycle[n + 1];
# $cycle[-1] will be the culprit
my $cycle = shift;

# Adjust the line numbers
for my $i (0 .. $#$cycle - 1) {
$cycle->[$i]->[0] = $cycle->[$i + 1]->[0];
}
$cycle->[-1]->[0] = 0;

my $first = shift @$cycle;
my $last = pop @$cycle;

my $msg = "In file included";
printf "%s from %s,\n", $msg, $last->[1] if defined $last;

for my $header (reverse @$cycle) {
printf "%s from %s:%d%s\n",
" " x length $msg,
$header->[1], $header->[0],
$header->[1] eq $last->[1] ? ' <-- here' : '';
}

printf "%s:%d: warning: recursive header inclusion\n",
$first->[1], $first->[0];
}

# Find and print the smallest cycle starting in the specified node.
sub detect_cycles {
my @queue = map { [[0, $_]] } @_;
while(@queue) {
my $top = pop @queue;
my $name = $top->[-1]->[1];

for my $dep (@{$deps{$name}}) {
my $chain = [@$top, [$dep->[0], $dep->[1]]];

# If the dep already exists in the chain, we have a
# cycle...
if(grep { $_->[1] eq $dep->[1] } @$top) {
print_cycle($chain);
next if $opt_all;
return;
}

push @queue, $chain;
}
}
}

sub mangle {
$_ = shift;
s/\//__/g;
s/\./_/g;
s/-/_/g;
$_;
}

# Output dependency graph in GraphViz language.
sub graph {
print "digraph {\n";

print "\t/* vertices */\n";
for my $header (keys %deps) {
printf "\t%s [label=\"%s\"];\n",
mangle($header), $header;
}

print "\n";

print "\t/* edges */\n";
for my $header (keys %deps) {
for my $dep (@{$deps{$header}}) {
printf "\t%s -> %s;\n",
mangle($header), mangle($dep->[1]);
}
}

print "}\n";
}