From 3b33d912c4e0be9e64be25a18252317dfb227dcf Mon Sep 17 00:00:00 2001
From: John Cupitt <jcupitt@gmail.com>
Date: Thu, 15 Sep 2022 12:57:36 +0100
Subject: [PATCH] fix an undefined shift

---
 libvips/foreign/heifload.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/libvips/foreign/heifload.c b/libvips/foreign/heifload.c
index 2a9f371b..83aed76d 100644
--- a/libvips/foreign/heifload.c
+++ b/libvips/foreign/heifload.c
@@ -306,11 +306,12 @@ static int
 vips_foreign_load_heif_is_a( const char *buf, int len )
 {
 	if( len >= 12 ) {
-		const guint32 chunk_len = 
-			(unsigned char) buf[0] << 24 |
-			(unsigned char) buf[1] << 16 |
-			(unsigned char) buf[2] << 8 |
-			(unsigned char) buf[3];
+                unsigned char *p = (unsigned char *) buf;
+		guint32 chunk_len = 
+			VIPS_LSHIFT_INT( p[0], 24 ) |
+			VIPS_LSHIFT_INT( p[1], 16 ) |
+			VIPS_LSHIFT_INT( p[2], 8 ) |
+			VIPS_LSHIFT_INT( p[3], 0 );
 
 		int i;