[master] 7ff657171 Add missing libunwind error handling

[Dridi Boukelmoune]

commit 7ff657171e0c7cec53f1eb09c2c34aca20f9178a
Author: Dridi Boukelmoune <dridi.boukelmoune at gmail.com>
Date:   Sun Sep 29 13:59:04 2019 +0200

    Add missing libunwind error handling
    
    Spotted-By: Coverity Scan

diff --git a/bin/varnishd/cache/cache_panic.c b/bin/varnishd/cache/cache_panic.c
index cd4cfc482..aa9d914b7 100644
--- a/bin/varnishd/cache/cache_panic.c
+++ b/bin/varnishd/cache/cache_panic.c
@@ -30,10 +30,11 @@
 #include "config.h"
 
 #ifdef WITH_UNWIND
-#include <libunwind.h>
+#  include <libunwind.h>
 #else
-#include <execinfo.h>
+#  include <execinfo.h>
 #endif
+
 #include <stdio.h>
 #include <stdlib.h>
 #include <signal.h>
@@ -633,7 +634,7 @@ pan_backtrace(struct vsb *vsb)
 		    "(unw_getcontext returned %d)\n", ret);
 		return;
 	}
-	unw_init_local(&cursor, &uc);
+	ret = unw_init_local(&cursor, &uc);
 	if (ret != 0) {
 		VSB_printf(vsb, "Backtrace not available "
 		    "(unw_init_local returned %d)\n", ret);