Add a reference counter to a structure used internally by the Tcl interface so that it does not segfault if the database connection is closed from any of the various callback scripts that may be invoked.

FossilOrigin-Name: e54a33ce56432b23947583d34cf12fc64a55bbc49eb77c7f33cff5926df51070

1 files changed, 78 insertions, 52 deletions

diff --git a/src/tclsqlite.c b/src/tclsqlite.c
index 8874ab769..b9b78b42b 100644
--- a/src/tclsqlite.c
+++ b/src/tclsqlite.c
@@ -181,6 +181,7 @@ struct SqliteDb {
   int nVMStep;               /* Another statistic for most recent operation */
   int nTransaction;          /* Number of nested [transaction] methods */
   int openFlags;             /* Flags used to open.  (SQLITE_OPEN_URI) */
+  int nRef;                  /* Delete object when this reaches 0 */
 #ifdef SQLITE_TEST
   int bLegacyPrepare;        /* True to use sqlite3_prepare() */
 #endif
@@ -518,63 +519,83 @@ static void flushStmtCache(SqliteDb *pDb){
 }
 
 /*
+** Increment the reference counter on the SqliteDb object. The reference
+** should be released by calling delDatabaseRef().
+*/
+static void addDatabaseRef(SqliteDb *pDb){
+  pDb->nRef++;
+}
+
+/*
+** Decrement the reference counter associated with the SqliteDb object.
+** If it reaches zero, delete the object.
+*/
+static void delDatabaseRef(SqliteDb *pDb){
+  assert( pDb->nRef>0 );
+  pDb->nRef--;
+  if( pDb->nRef==0 ){
+    flushStmtCache(pDb);
+    closeIncrblobChannels(pDb);
+    sqlite3_close(pDb->db);
+    while( pDb->pFunc ){
+      SqlFunc *pFunc = pDb->pFunc;
+      pDb->pFunc = pFunc->pNext;
+      assert( pFunc->pDb==pDb );
+      Tcl_DecrRefCount(pFunc->pScript);
+      Tcl_Free((char*)pFunc);
+    }
+    while( pDb->pCollate ){
+      SqlCollate *pCollate = pDb->pCollate;
+      pDb->pCollate = pCollate->pNext;
+      Tcl_Free((char*)pCollate);
+    }
+    if( pDb->zBusy ){
+      Tcl_Free(pDb->zBusy);
+    }
+    if( pDb->zTrace ){
+      Tcl_Free(pDb->zTrace);
+    }
+    if( pDb->zTraceV2 ){
+      Tcl_Free(pDb->zTraceV2);
+    }
+    if( pDb->zProfile ){
+      Tcl_Free(pDb->zProfile);
+    }
+    if( pDb->zBindFallback ){
+      Tcl_Free(pDb->zBindFallback);
+    }
+    if( pDb->zAuth ){
+      Tcl_Free(pDb->zAuth);
+    }
+    if( pDb->zNull ){
+      Tcl_Free(pDb->zNull);
+    }
+    if( pDb->pUpdateHook ){
+      Tcl_DecrRefCount(pDb->pUpdateHook);
+    }
+    if( pDb->pPreUpdateHook ){
+      Tcl_DecrRefCount(pDb->pPreUpdateHook);
+    }
+    if( pDb->pRollbackHook ){
+      Tcl_DecrRefCount(pDb->pRollbackHook);
+    }
+    if( pDb->pWalHook ){
+      Tcl_DecrRefCount(pDb->pWalHook);
+    }
+    if( pDb->pCollateNeeded ){
+      Tcl_DecrRefCount(pDb->pCollateNeeded);
+    }
+    Tcl_Free((char*)pDb);
+  }
+}
+
+/*
 ** TCL calls this procedure when an sqlite3 database command is
 ** deleted.
 */
 static void SQLITE_TCLAPI DbDeleteCmd(void *db){
   SqliteDb *pDb = (SqliteDb*)db;
-  flushStmtCache(pDb);
-  closeIncrblobChannels(pDb);
-  sqlite3_close(pDb->db);
-  while( pDb->pFunc ){
-    SqlFunc *pFunc = pDb->pFunc;
-    pDb->pFunc = pFunc->pNext;
-    assert( pFunc->pDb==pDb );
-    Tcl_DecrRefCount(pFunc->pScript);
-    Tcl_Free((char*)pFunc);
-  }
-  while( pDb->pCollate ){
-    SqlCollate *pCollate = pDb->pCollate;
-    pDb->pCollate = pCollate->pNext;
-    Tcl_Free((char*)pCollate);
-  }
-  if( pDb->zBusy ){
-    Tcl_Free(pDb->zBusy);
-  }
-  if( pDb->zTrace ){
-    Tcl_Free(pDb->zTrace);
-  }
-  if( pDb->zTraceV2 ){
-    Tcl_Free(pDb->zTraceV2);
-  }
-  if( pDb->zProfile ){
-    Tcl_Free(pDb->zProfile);
-  }
-  if( pDb->zBindFallback ){
-    Tcl_Free(pDb->zBindFallback);
-  }
-  if( pDb->zAuth ){
-    Tcl_Free(pDb->zAuth);
-  }
-  if( pDb->zNull ){
-    Tcl_Free(pDb->zNull);
-  }
-  if( pDb->pUpdateHook ){
-    Tcl_DecrRefCount(pDb->pUpdateHook);
-  }
-  if( pDb->pPreUpdateHook ){
-    Tcl_DecrRefCount(pDb->pPreUpdateHook);
-  }
-  if( pDb->pRollbackHook ){
-    Tcl_DecrRefCount(pDb->pRollbackHook);
-  }
-  if( pDb->pWalHook ){
-    Tcl_DecrRefCount(pDb->pWalHook);
-  }
-  if( pDb->pCollateNeeded ){
-    Tcl_DecrRefCount(pDb->pCollateNeeded);
-  }
-  Tcl_Free((char*)pDb);
+  delDatabaseRef(pDb);
 }
 
 /*
@@ -1246,6 +1267,7 @@ static int SQLITE_TCLAPI DbTransPostCmd(
   }
   pDb->disableAuth--;
 
+  delDatabaseRef(pDb);
   return rc;
 }
 
@@ -1579,6 +1601,7 @@ static void dbEvalInit(
     Tcl_IncrRefCount(pArray);
   }
   p->evalFlags = evalFlags;
+  addDatabaseRef(p->pDb);
 }
 
 /*
@@ -1719,6 +1742,7 @@ static void dbEvalFinalize(DbEvalContext *p){
   }
   Tcl_DecrRefCount(p->pSql);
   dbReleaseColumnNames(p);
+  delDatabaseRef(p->pDb);
 }
 
 /*
@@ -3435,6 +3459,7 @@ deserialize_error:
     ** opened above. If not using NRE, evaluate the script directly, then
     ** call function DbTransPostCmd() to commit (or rollback) the transaction
     ** or savepoint.  */
+    addDatabaseRef(pDb);          /* DbTransPostCmd() calls delDatabaseRef() */
     if( DbUseNre() ){
       Tcl_NRAddCallback(interp, DbTransPostCmd, cd, 0, 0, 0);
       (void)Tcl_NREvalObj(interp, pScript, 0);
@@ -3842,6 +3867,7 @@ static int SQLITE_TCLAPI DbMain(
   }else{
     Tcl_CreateObjCommand(interp, zArg, DbObjCmd, (char*)p, DbDeleteCmd);
   }
+  p->nRef = 1;
   return TCL_OK;
 }