From 8aead43028c0320d755f06a7d43dd34e0e709278 Mon Sep 17 00:00:00 2001
From: David Phillips <dbphillipsnz@gmail.com>
Date: Tue, 26 Apr 2016 14:09:32 +1200
Subject: Add catch for non-positive white value

---
 pgm-interlace.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/pgm-interlace.c b/pgm-interlace.c
index 861f30b..21226a7 100644
--- a/pgm-interlace.c
+++ b/pgm-interlace.c
@@ -45,6 +45,12 @@ int check_sanity(long width, long height, long white, unsigned int clust_total)
 		return 1;
 	}
 
+	if (white <= 0)
+	{
+		fprintf(stderr, "white value must be positive\n");
+		return 1;
+	}
+
 	/* FIXME only support single-byte pixels, PGM supports 16-bit according
 	 * to <http://netpbm.sourceforge.net/doc/pgm.html> */
 	if (white > 255)
-- 
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