[debhelper-devel] [debhelper] 01/01: Avoid calling dpkg-architecture on each unknown value

[Niels Thykier]

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nthykier pushed a commit to branch master
in repository debhelper.

commit 6b05acdf097f3ff8c0e82f641c160f4f6ca29f67
Author: Niels Thykier <niels at thykier.net>
Date:   Sat Feb 18 21:00:16 2017 +0000

    Avoid calling dpkg-architecture on each unknown value
    
    Call dpkg-architecture at most once (per process) - even if
    dpkg_architecture_value() is passed unknown variables.
    
    Signed-off-by: Niels Thykier <niels at thykier.net>
---
 Debian/Debhelper/Dh_Lib.pm | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/Debian/Debhelper/Dh_Lib.pm b/Debian/Debhelper/Dh_Lib.pm
index aa7eaf1..1d2bde1 100644
--- a/Debian/Debhelper/Dh_Lib.pm
+++ b/Debian/Debhelper/Dh_Lib.pm
@@ -855,15 +855,18 @@ sub excludefile {
 			return $ENV{$var};
 		}
 		elsif (! exists($dpkg_arch_output{$var})) {
-			local $_;
-			open(PIPE, '-|', 'dpkg-architecture')
+			# Return here if we already consulted dpkg-architecture
+			# (saves a fork+exec on unknown variables)
+			return if %dpkg_arch_output;
+
+			open(my $fd, '-|', 'dpkg-architecture')
 				or error("dpkg-architecture failed");
-			while (<PIPE>) {
-				chomp;
-				my ($k, $v) = split(/=/, $_, 2);
+			while (my $line = <$fd>) {
+				chomp($line);
+				my ($k, $v) = split(/=/, $line, 2);
 				$dpkg_arch_output{$k} = $v;
 			}
-			close(PIPE);
+			close($fd);
 		}
 		return $dpkg_arch_output{$var};
 	}

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