Merge #19111: Limit scope of all global std::once_flag

fa9c67559186f5416c1c0b26c0a1d5e72c234ccb Limit scope of all global std::once_flag (MarcoFalke)

Pull request description:

  `once_flag` is  a helper (as the name might suggest) to execute a callable only once. Thus, the scope of the flag does never need to extend beyond where the callable is called. Typically this is function scope.

  Move all the flags to function scope to
  * simplify code review
  * avoid mistakes where similarly named flags are accidentally exchanged
  * avoid polluting the global scope

ACKs for top commit:
  hebasto:
    ACK fa9c67559186f5416c1c0b26c0a1d5e72c234ccb, tested on Linux Mint 19.3 (x86_64).
  promag:
    Code review ACK fa9c67559186f5416c1c0b26c0a1d5e72c234ccb.

Tree-SHA512: 095a0c11d93d0ddcb82b3c71676090ecc7e3de3d5e7a2a63ab2583093be279242acac43523bbae2060b4dcfa8f92b54256a0e91fbbae78fa92d2d49e9db62e57

3 files changed, 4 insertions, 5 deletions

diff --git a/src/rpc/server.cpp b/src/rpc/server.cpp
index 2a0079ac39..844f62cbc6 100644
--- a/src/rpc/server.cpp
+++ b/src/rpc/server.cpp
@@ -22,8 +22,6 @@
 
 static RecursiveMutex cs_rpcWarmup;
 static std::atomic<bool> g_rpc_running{false};
-static std::once_flag g_rpc_interrupt_flag;
-static std::once_flag g_rpc_stop_flag;
 static bool fRPCInWarmup GUARDED_BY(cs_rpcWarmup) = true;
 static std::string rpcWarmupStatus GUARDED_BY(cs_rpcWarmup) = "RPC server started";
 /* Timer-creating functions */
@@ -295,6 +293,7 @@ void StartRPC()
 
 void InterruptRPC()
 {
+    static std::once_flag g_rpc_interrupt_flag;
     // This function could be called twice if the GUI has been started with -server=1.
     std::call_once(g_rpc_interrupt_flag, []() {
         LogPrint(BCLog::RPC, "Interrupting RPC\n");
@@ -305,6 +304,7 @@ void InterruptRPC()
 
 void StopRPC()
 {
+    static std::once_flag g_rpc_stop_flag;
     // This function could be called twice if the GUI has been started with -server=1.
     assert(!g_rpc_running);
     std::call_once(g_rpc_stop_flag, []() {
diff --git a/src/support/lockedpool.cpp b/src/support/lockedpool.cpp
index f17b539e09..b4f392116c 100644
--- a/src/support/lockedpool.cpp
+++ b/src/support/lockedpool.cpp
@@ -29,7 +29,6 @@
 #endif
 
 LockedPoolManager* LockedPoolManager::_instance = nullptr;
-std::once_flag LockedPoolManager::init_flag;
 
 /*******************************************************************************/
 // Utilities
diff --git a/src/support/lockedpool.h b/src/support/lockedpool.h
index de668f0773..b9e2e99d1a 100644
--- a/src/support/lockedpool.h
+++ b/src/support/lockedpool.h
@@ -221,7 +221,8 @@ public:
     /** Return the current instance, or create it once */
     static LockedPoolManager& Instance()
     {
-        std::call_once(LockedPoolManager::init_flag, LockedPoolManager::CreateInstance);
+        static std::once_flag init_flag;
+        std::call_once(init_flag, LockedPoolManager::CreateInstance);
         return *LockedPoolManager::_instance;
     }
 
@@ -234,7 +235,6 @@ private:
     static bool LockingFailed();
 
     static LockedPoolManager* _instance;
-    static std::once_flag init_flag;
 };
 
 #endif // BITCOIN_SUPPORT_LOCKEDPOOL_H