diff --git a/libraries/chain/include/eosio/chain/transaction_object.hpp b/libraries/chain/include/eosio/chain/transaction_object.hpp
index d43b449be4..301988e33d 100644
--- a/libraries/chain/include/eosio/chain/transaction_object.hpp
+++ b/libraries/chain/include/eosio/chain/transaction_object.hpp
@@ -42,7 +42,6 @@ namespace eosio { namespace chain {
       >
    >;
 
-   typedef chainbase::generic_index<transaction_multi_index> transaction_index;
 } }
 
 CHAINBASE_SET_INDEX_TYPE(eosio::chain::transaction_object, eosio::chain::transaction_multi_index)
diff --git a/libraries/libfc/include/fc/mutex.hpp b/libraries/libfc/include/fc/mutex.hpp
index 518a9ccd8b..eaa1a13883 100644
--- a/libraries/libfc/include/fc/mutex.hpp
+++ b/libraries/libfc/include/fc/mutex.hpp
@@ -127,13 +127,13 @@ class SCOPED_CAPABILITY lock_guard {
 
 public:
    // Acquire mu, implicitly acquire *this and associate it with mu.
-   lock_guard(M& mu) ACQUIRE(mu)
+   [[nodiscard]] lock_guard(M& mu) ACQUIRE(mu)
       : mut(mu) {
       mu.lock();
    }
 
    // Assume mu is held, implicitly acquire *this and associate it with mu.
-   lock_guard(M& mu, adopt_lock_t) REQUIRES(mu)
+   [[nodiscard]] lock_guard(M& mu, adopt_lock_t) REQUIRES(mu)
       : mut(mu) {}
 
    ~lock_guard() RELEASE() { mut.unlock(); }
@@ -150,24 +150,24 @@ class SCOPED_CAPABILITY unique_lock {
    bool locked;
 
 public:
-   unique_lock() noexcept
+   [[nodiscard]] unique_lock() noexcept
       : mut(nullptr)
       , locked(false) {}
 
    // Acquire mu, implicitly acquire *this and associate it with mu.
-   explicit unique_lock(M& mu) ACQUIRE(mu)
+   [[nodiscard]] explicit unique_lock(M& mu) ACQUIRE(mu)
       : mut(&mu)
       , locked(true) {
       mut->lock();
    }
 
    // Assume mu is held, implicitly acquire *this and associate it with mu.
-   unique_lock(M& mu, adopt_lock_t) REQUIRES(mu)
+   [[nodiscard]] unique_lock(M& mu, adopt_lock_t) REQUIRES(mu)
       : mut(&mu)
       , locked(true) {}
 
    // Assume mu is not held, implicitly acquire *this and associate it with mu.
-   unique_lock(M& mu, defer_lock_t) EXCLUDES(mu)
+   [[nodiscard]] unique_lock(M& mu, defer_lock_t) EXCLUDES(mu)
       : mut(mu)
       , locked(false) {}
 
diff --git a/libraries/libfc/include/fc/scoped_exit.hpp b/libraries/libfc/include/fc/scoped_exit.hpp
index 8cae626b87..657bfe6a08 100644
--- a/libraries/libfc/include/fc/scoped_exit.hpp
+++ b/libraries/libfc/include/fc/scoped_exit.hpp
@@ -8,9 +8,9 @@ namespace fc {
    class scoped_exit {
       public:
          template<typename C>
-         scoped_exit( C&& c ):callback( std::forward<C>(c) ){}
+         [[nodiscard]] scoped_exit( C&& c ):callback( std::forward<C>(c) ){}
 
-         scoped_exit( scoped_exit&& mv )
+         [[nodiscard]] scoped_exit( scoped_exit&& mv )
          :callback( std::move( mv.callback ) ),canceled(mv.canceled)
          {
             mv.canceled = true;