chain: define enum used as bit field as uint32_t

Bitwise logic combined with `<` with undefined signedness will
potentially results in undefined behavior. Fix this by defining the type
as a c++11 typed enum.

Fixes #6017.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/chain.h b/src/chain.h
index 5b9605a80..017d4fe45 100644
--- a/src/chain.h
+++ b/src/chain.h
@@ -54,7 +54,7 @@ struct CDiskBlockPos
 
 };
 
-enum BlockStatus {
+enum BlockStatus: uint32_t {
     //! Unused.
     BLOCK_VALID_UNKNOWN      =    0,