1 files changed, 48 insertions, 1 deletions

diff --git a/src/prepare.c b/src/prepare.c
index 3a2943f10..f93a6f07a 100644
--- a/src/prepare.c
+++ b/src/prepare.c
@@ -570,8 +570,16 @@ void sqlite3ParserReset(Parse *pParse){
     agginfoFree(db, pThis);
     pThis = pNext;
   }
+  while( pParse->pCleanup ){
+    ParseCleanup *pThis = pParse->pCleanup;
+    pParse->pCleanup = pThis->pNext;
+    pThis->xCleanup(db, pThis->pPtr);
+    sqlite3DbFree(db, pThis);
+  }
   sqlite3DbFree(db, pParse->aLabel);
-  sqlite3ExprListDelete(db, pParse->pConstExpr);
+  if( pParse->pConstExpr ){
+    sqlite3ExprListDelete(db, pParse->pConstExpr);
+  }
   if( db ){
     assert( db->lookaside.bDisable >= pParse->disableLookaside );
     db->lookaside.bDisable -= pParse->disableLookaside;
@@ -581,6 +589,45 @@ void sqlite3ParserReset(Parse *pParse){
 }
 
 /*
+** Add a new cleanup operation to a Parser.  The cleanup should happen when
+** the parser object is destroyed.  But, beware: the cleanup might happen
+** immediately.
+**
+** Use this mechanism for uncommon cleanups.  There is a higher setup
+** cost for this mechansim (an extra malloc), so it should not be used
+** for common cleanups that happen on most calls.  But for less
+** common cleanups, we save a single NULL-pointer comparison in
+** sqlite3ParserReset(), which reduces the total CPU cycle count.
+**
+** If a memory allocation error occurs, then the cleanup happens immediately.
+** When eithr SQLITE_DEBUG or SQLITE_COVERAGE_TEST are defined, the
+** pParse->earlyCleanup flag is set in that case.  Calling code show verify
+** that test cases exist for which this happens, to guard against possible
+** use-after-free errors following an OOM.  The preferred way to do this is
+** to immediately follow the call to this routine with:
+**
+**       testcase( pParse->earlyCleanup );
+*/
+void sqlite3ParserAddCleanup(
+  Parse *pParse,                      /* Destroy when this Parser finishes */
+  void (*xCleanup)(sqlite3*,void*),   /* The cleanup routine */
+  void *pPtr                          /* Pointer to object to be cleaned up */
+){
+  ParseCleanup *pCleanup = sqlite3DbMallocRaw(pParse->db, sizeof(*pCleanup));
+  if( pCleanup ){
+    pCleanup->pNext = pParse->pCleanup;
+    pParse->pCleanup = pCleanup;
+    pCleanup->pPtr = pPtr;
+    pCleanup->xCleanup = xCleanup;
+  }else{
+    xCleanup(pParse->db, pPtr);
+#if defined(SQLITE_DEBUG) || defined(SQLITE_COVERAGE_TEST)
+    pParse->earlyCleanup = 1;
+#endif
+  }
+}
+
+/*
 ** Compile the UTF-8 encoded SQL statement zSql into a statement handle.
 */
 static int sqlite3Prepare(