Avoid passing NULL to printf %s specifier

2 files changed, 13 insertions, 5 deletions

diff --git a/src/internal.h b/src/internal.h
index f0c3d7dd13..696e5db1a3 100644
--- a/src/internal.h
+++ b/src/internal.h
@@ -7,6 +7,7 @@
 
 #include <errno.h>
 #include <limits.h>
+#include <verify.h>
 
 #ifdef HAVE_SYS_SYSLIMITS_H
 #include <sys/syslimits.h>
@@ -115,6 +116,13 @@
 #define ATTRIBUTE_RETURN_CHECK
 #endif				/* __GNUC__ */
 
+/*
+ * Use this when passing possibly-NULL strings to printf-a-likes.
+ */
+#define NULLSTR(s) \
+    ((void)verify_true(sizeof *(s) == sizeof (char)), \
+     (s) ? (s) : "(null)")
+
 /**
  * TODO:
  *
diff --git a/src/libvirt.c b/src/libvirt.c
index 37eaa63a3e..a96eecd40b 100644
--- a/src/libvirt.c
+++ b/src/libvirt.c
@@ -852,10 +852,10 @@ do_open (const char *name,
               "  port %d\n"
               "  path %s\n",
               name,
-              ret->uri->scheme, ret->uri->opaque,
-              ret->uri->authority, ret->uri->server,
-              ret->uri->user, ret->uri->port,
-              ret->uri->path);
+              NULLSTR(ret->uri->scheme), NULLSTR(ret->uri->opaque),
+              NULLSTR(ret->uri->authority), NULLSTR(ret->uri->server),
+              NULLSTR(ret->uri->user), ret->uri->port,
+              NULLSTR(ret->uri->path));
     } else {
         DEBUG0("no name, allowing driver auto-select");
     }
@@ -1044,7 +1044,7 @@ virConnectOpenAuth(const char *name,
         if (virInitialize() < 0)
             return NULL;
 
-    DEBUG("name=%s, auth=%p, flags=%d", name, auth, flags);
+    DEBUG("name=%s, auth=%p, flags=%d", NULLSTR(name), auth, flags);
     return do_open (name, auth, flags);
 }