From: Ben Pfaff <blp@cs.stanford.edu>
Date: Tue, 9 Feb 2016 04:46:18 +0000 (-0800)
Subject: pintos: Fix undefined value warning from Perl on read error.
X-Git-Url: https://pintos-os.org/cgi-bin/gitweb.cgi?p=pintos-anon;a=commitdiff_plain;h=161bf03beb0aae6ad38aa884cd534a94737d396a

pintos: Fix undefined value warning from Perl on read error.

When sysread encounters an error, it returns undef, which yields a warning
when compared against 0.  This fixes the problem.
---

diff --git a/src/utils/pintos b/src/utils/pintos
index eca4708..1564216 100755
--- a/src/utils/pintos
+++ b/src/utils/pintos
@@ -827,8 +827,8 @@ sub xsystem {
 
 		# Read and print out pipe data.
 		my ($len) = length ($buf);
-		waitpid ($pid, 0), last
-		  if sysread ($in, $buf, 4096, $len) <= 0;
+		my ($n_read) = sysread ($in, $buf, 4096, $len);
+		waitpid ($pid, 0), last if !defined ($n_read) || $n_read <= 0;
 		print substr ($buf, $len);
 
 		# Remove full lines from $buf and scan them for keywords.