-# Derived class can call this method in its constructor to enforce
-# outside-source building even if the user didn't request it.
-sub enforce_outside_source_building {
- my ($this, $builddir) = @_;
- if (!defined $this->{builddir}) {
- $this->{builddir} = ($builddir && $builddir ne ".") ? $builddir : $this->DEFAULT_BUILD_DIRECTORY();
+# Derived class can call this method in its constructor to *prefer*
+# out of source building. Unless build directory has already been
+# specified building will proceed in the DEFAULT_BUILD_DIRECTORY or
+# the one specified in the 'builddir' named parameter (which may
+# match the source directory). Typically you should pass @_ from
+# the constructor to this call.
+sub prefer_out_of_source_building {
+ my $this=shift;
+ my %args=@_;
+ if (!defined $this->get_builddir()) {
+ if (!$this->_set_builddir($args{builddir}) && !$args{builddir}) {
+ # If we are here, DEFAULT_BUILD_DIRECTORY matches
+ # the source directory, building might fail.
+ error("default build directory is the same as the source directory." .
+ " Please specify a custom build directory");
+ }
+ }
+}
+
+# Enhanced version of File::Spec::canonpath. It collapses ..
+# too so it may return invalid path if symlinks are involved.
+# On the other hand, it does not need for the path to exist.
+sub canonpath {
+ my ($this, $path)=@_;
+ my @canon;
+ my $back=0;
+ for my $comp (split(m%/+%, $path)) {
+ if ($comp eq '.') {
+ next;
+ }
+ elsif ($comp eq '..') {
+ if (@canon > 0) { pop @canon; } else { $back++; }
+ }
+ else {
+ push @canon, $comp;
+ }
+ }
+ return (@canon + $back > 0) ? join('/', ('..')x$back, @canon) : '.';
+}
+
+# Given both $path and $base are relative to the $root, converts and
+# returns path of $path being relative to the $base. If either $path or
+# $base is absolute, returns another $path (converted to) absolute.
+sub _rel2rel {
+ my ($this, $path, $base, $root)=@_;
+ $root = $this->{cwd} unless defined $root;
+
+ if (File::Spec->file_name_is_absolute($path)) {
+ return $path;