Merge #16092: Don't use global (external) symbols for symbols that are used in only one translation unit

0959d37e3e Don't use global (external) symbols for symbols that are used in only one translation unit (practicalswift)

Pull request description:

  Don't use global (external) symbols for symbols that are used in only one translation unit.

  Before:

  ```
  $ for SYMBOL in $(nm src/bitcoind | grep -E ' [BD] ' | c++filt | cut -f3- -d' ' | grep -v @ | grep -v : | sort | grep '[a-z]' | sort -u | grep -vE '(^_|typeinfo|vtable)'); do
        REFERENCES=$(git grep -lE "([^a-zA-Z]|^)${SYMBOL}([^a-zA-Z]|\$)" -- "*.cpp" "*.h")
        N_REFERENCES=$(wc -l <<< "${REFERENCES}")
        if [[ ${N_REFERENCES} > 1 ]]; then
            continue
        fi
        echo "Global symbol ${SYMBOL} is used in only one translation unit: ${REFERENCES}"
    done
  Global symbol g_chainstate is used in only one translation unit: src/validation.cpp
  Global symbol g_ui_signals is used in only one translation unit: src/ui_interface.cpp
  Global symbol instance_of_cmaincleanup is used in only one translation unit: src/validation.cpp
  Global symbol instance_of_cnetcleanup is used in only one translation unit: src/net.cpp
  Global symbol instance_of_cnetprocessingcleanup is used in only one translation unit: src/net_processing.cpp
  Global symbol pindexBestForkBase is used in only one translation unit: src/validation.cpp
  Global symbol pindexBestForkTip is used in only one translation unit: src/validation.cpp
  $
  ```

  After:

  ```
  $ for SYMBOL in $(nm src/bitcoind | grep -E ' [BD] ' | c++filt | cut -f3- -d' ' | grep -v @ | grep -v : | sort | grep '[a-z]' | sort -u | grep -vE '(^_|typeinfo|vtable)'); do
        REFERENCES=$(git grep -lE "([^a-zA-Z]|^)${SYMBOL}([^a-zA-Z]|\$)" -- "*.cpp" "*.h")
        N_REFERENCES=$(wc -l <<< "${REFERENCES}")
        if [[ ${N_REFERENCES} > 1 ]]; then
            continue
        fi
        echo "Global symbol ${SYMBOL} is used in only one translation unit: ${REFERENCES}"
    done
  $
  ```

  ♻️ Think about future generations: save the global namespace from unnecessary pollution!  ♻️

ACKs for commit 0959d3:
  Empact:
    ACK https://github.com/bitcoin/bitcoin/pull/16092/commits/0959d37e3e0f80010a78d175e3846dabf5d35919
  MarcoFalke:
    ACK 0959d37e3e0f80010a78d175e3846dabf5d35919
  hebasto:
    ACK 0959d37e3e0f80010a78d175e3846dabf5d35919
  promag:
    ACK 0959d37.

Tree-SHA512: 722f66bb50450f19b57e8a8fbe949f30cd651eb8564e5787cbb772a539bf3a288c048dc49e655fd73ece6a46f6dafade515ec4004729bf2b3ab83117b7c5d153

4 files changed, 10 insertions, 7 deletions

diff --git a/src/net.cpp b/src/net.cpp
index 3c6f5a05f3..75a47d7ad2 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -2287,8 +2287,8 @@ public:
         WSACleanup();
 #endif
     }
-}
-instance_of_cnetcleanup;
+};
+static CNetCleanup instance_of_cnetcleanup;
 
 void CConnman::Interrupt()
 {
diff --git a/src/net_processing.cpp b/src/net_processing.cpp
index e57706980a..5ff456fcb0 100644
--- a/src/net_processing.cpp
+++ b/src/net_processing.cpp
@@ -4086,4 +4086,5 @@ public:
         mapOrphanTransactions.clear();
         mapOrphanTransactionsByPrev.clear();
     }
-} instance_of_cnetprocessingcleanup;
+};
+static CNetProcessingCleanup instance_of_cnetprocessingcleanup;
diff --git a/src/ui_interface.cpp b/src/ui_interface.cpp
index 746514a01f..d310637145 100644
--- a/src/ui_interface.cpp
+++ b/src/ui_interface.cpp
@@ -21,7 +21,8 @@ struct UISignals {
     boost::signals2::signal<CClientUIInterface::NotifyBlockTipSig> NotifyBlockTip;
     boost::signals2::signal<CClientUIInterface::NotifyHeaderTipSig> NotifyHeaderTip;
     boost::signals2::signal<CClientUIInterface::BannedListChangedSig> BannedListChanged;
-} g_ui_signals;
+};
+static UISignals g_ui_signals;
 
 #define ADD_SIGNALS_IMPL_WRAPPER(signal_name)                                                                 \
     boost::signals2::connection CClientUIInterface::signal_name##_connect(std::function<signal_name##Sig> fn) \
diff --git a/src/validation.cpp b/src/validation.cpp
index 3026df34fe..2d2252c251 100644
--- a/src/validation.cpp
+++ b/src/validation.cpp
@@ -77,7 +77,7 @@ bool CBlockIndexWorkComparator::operator()(const CBlockIndex *pa, const CBlockIn
     return false;
 }
 
-CChainState g_chainstate;
+static CChainState g_chainstate;
 
 CChainState& ChainstateActive() { return g_chainstate; }
 
@@ -1044,7 +1044,7 @@ bool CChainState::IsInitialBlockDownload() const
     return false;
 }
 
-CBlockIndex *pindexBestForkTip = nullptr, *pindexBestForkBase = nullptr;
+static CBlockIndex *pindexBestForkTip = nullptr, *pindexBestForkBase = nullptr;
 
 static void AlertNotify(const std::string& strMessage)
 {
@@ -4757,4 +4757,5 @@ public:
             delete (*it1).second;
         mapBlockIndex.clear();
     }
-} instance_of_cmaincleanup;
+};
+static CMainCleanup instance_of_cmaincleanup;