lib/core: add failsafe to UTF8Codec::decode_string

Calling decode_string on the UTF-8 codec with a negative legth would
cause memmove to crash the program with a segfault.

Adding an assert gives more information on what went wrong and will help
investigate future bugs.

Signed-off-by: Lucas Bajolet <lucas.bajolet@gmail.com>

diff --git a/lib/core/codecs/utf8.nit b/lib/core/codecs/utf8.nit
index 43f6235..d4d4a38 100644 (file)
--- a/lib/core/codecs/utf8.nit
+++ b/lib/core/codecs/utf8.nit
@@ -68,6 +68,7 @@ private class UTF8Codec
        end
 
        redef fun decode_string(ns, len) do
+               assert len >= 0
                var ret = ns.to_s_unsafe(len, copy=false)
                var rit = ret.as(FlatString).items
                if rit == ns then