[glib/wip/smcv/memcmp-null: 2/2] gbytes: Avoid memcmp (NULL, ., 0) or memcmp (., NULL, 0)

[Simon McVittie <smcv src gnome org>]

commit 8235bbe467be78befe56e7a5dc914e5e35785fa3
Author: Simon McVittie <smcv collabora com>
Date:   Mon Nov 4 13:41:14 2019 +0000

    gbytes: Avoid memcmp (NULL, ., 0) or memcmp (., NULL, 0)
    
    Similar to 3837b83f, glibc memcmp is declared with the first two
    arguments annotated as non-null via an attribute, which results in the
    undefined behaviour sanitizer considering it to be UB to pass a null
    pointer there (even if we are comparing 0 bytes, and hence not actually
    dereferencing the pointer).
    
    This shows up in /gvariant/serialiser/children when run with the
    undefined behaviour sanitizer.
    
    Signed-off-by: Simon McVittie <smcv collabora com>

 glib/gbytes.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/glib/gbytes.c b/glib/gbytes.c
index 7b72886e5..ec6923188 100644
--- a/glib/gbytes.c
+++ b/glib/gbytes.c
@@ -365,7 +365,7 @@ g_bytes_equal (gconstpointer bytes1,
   g_return_val_if_fail (bytes2 != NULL, FALSE);
 
   return b1->size == b2->size &&
-         memcmp (b1->data, b2->data, b1->size) == 0;
+         (b1->size == 0 || memcmp (b1->data, b2->data, b1->size) == 0);
 }
 
 /**