scons: Enable -Wextra by default

Make best use of the compiler, and enable -Wextra as well as
-Wall. There are a few issues that had to be resolved, but they are
all trivial.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/dev/net/pktfifo.hh b/src/dev/net/pktfifo.hh
index 5ef75423c..456c4433b 100644
--- a/src/dev/net/pktfifo.hh
+++ b/src/dev/net/pktfifo.hh
@@ -106,8 +106,8 @@ class PacketFifo
     unsigned
     reserve(unsigned len = 0)
     {
+        assert(avail() >= len);
         _reserved += len;
-        assert(avail() >= 0);
         return _reserved;
     }