media-gfx/zbar/files/zbar-0.23_fix_detection_of_errors_in_the_v4l_read.patch


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From 52a4fa5242af5da770b3cab1713f87e8d899e7ed Mon Sep 17 00:00:00 2001
From: Dan Fandrich <dan@coneharvesters.com>
Date: Fri, 27 Dec 2019 18:33:17 +0100
Subject: [PATCH] Fix detection of errors in the v4l read.

The return type must be signed in order to detect a read failure. Also,
display an error message after such a failure.
---
 zbar/video/v4l2.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/zbar/video/v4l2.c b/zbar/video/v4l2.c
index daed38b..c0398ea 100644
--- a/zbar/video/v4l2.c
+++ b/zbar/video/v4l2.c
@@ -133,9 +133,11 @@ static zbar_image_t *v4l2_dq (zbar_video_t *vdo)
             return(NULL);
 
         /* FIXME should read entire image */
-        unsigned long datalen = read(fd, (void*)img->data, img->datalen);
-        if(datalen < 0)
+        ssize_t datalen = read(fd, (void*)img->data, img->datalen);
+        if(datalen < 0) {
+            perror("v4l2_dq read");
             return(NULL);
+        }
         else if(datalen != img->datalen)
             zprintf(0, "WARNING: read() size mismatch: 0x%lx != 0x%lx\n",
                     datalen, img->datalen);