Index: test/fuzzcheck.c
==================================================================
--- test/fuzzcheck.c
+++ test/fuzzcheck.c
@@ -803,10 +803,11 @@
 "  --limit-vdbe         Panic if any test runs for more than 100,000 cycles\n"
 "  --load-sql ARGS...   Load SQL scripts fro files into SOURCE-DB\n"
 "  --load-db ARGS...    Load template databases from files into SOURCE_DB\n"
 "  -m TEXT              Add a description to the database\n"
 "  --native-vfs         Use the native VFS for initially empty database files\n"
+"  --native-malloc      Turn off MEMSYS3/5 and Lookaside\n"
 "  --oss-fuzz           Enable OSS-FUZZ testing\n"
 "  --prng-seed N        Seed value for the PRGN inside of SQLite\n"
 "  --rebuild            Rebuild and vacuum the database file\n"
 "  --result-trace       Show the results of each SQL command\n"
 "  --sqlid N            Use only SQL where sqlid=N\n"
@@ -849,10 +850,11 @@
   char *zExpDb = 0;            /* Write Databases to files in this directory */
   char *zExpSql = 0;           /* Write SQL to files in this directory */
   void *pHeap = 0;             /* Heap for use by SQLite */
   int ossFuzz = 0;             /* enable OSS-FUZZ testing */
   int ossFuzzThisDb = 0;       /* ossFuzz value for this particular database */
+  int nativeMalloc = 0;        /* Turn off MEMSYS3/5 and lookaside if true */
   sqlite3_vfs *pDfltVfs;       /* The default VFS */
 
   iBegin = timeOfDay();
 #ifdef __unix__
   signal(SIGALRM, timeoutHandler);
@@ -908,10 +910,13 @@
         break;
       }else
       if( strcmp(z,"m")==0 ){
         if( i>=argc-1 ) fatalError("missing arguments on %s", argv[i]);
         zMsg = argv[++i];
+      }else
+      if( strcmp(z,"native-malloc")==0 ){
+        nativeMalloc = 1;
       }else
       if( strcmp(z,"native-vfs")==0 ){
         nativeFlag = 1;
       }else
       if( strcmp(z,"oss-fuzz")==0 ){
@@ -1011,11 +1016,11 @@
         if( zName==0 ) continue;
         if( strcmp(zName, "oss-fuzz")==0 ){
           ossFuzzThisDb = sqlite3_column_int(pStmt,1);
           if( verboseFlag ) printf("Config: oss-fuzz=%d\n", ossFuzzThisDb);
         }
-        if( strcmp(zName, "limit-mem")==0 ){
+        if( strcmp(zName, "limit-mem")==0 && !nativeMalloc ){
 #if !defined(SQLITE_ENABLE_MEMSYS3) && !defined(SQLITE_ENABLE_MEMSYS5)
           fatalError("the limit-mem option requires -DSQLITE_ENABLE_MEMSYS5"
                      " or _MEMSYS3");
 #else
           nMemThisDb = sqlite3_column_int(pStmt,1);
@@ -1141,18 +1146,23 @@
     if( sqlite3_memory_used()>0 ){
       fatalError("SQLite has memory in use before the start of testing");
     }
 
     /* Limit available memory, if requested */
-    if( nMemThisDb>0 ){
-      sqlite3_shutdown();
+    sqlite3_shutdown();
+    if( nMemThisDb>0 && !nativeMalloc ){
       pHeap = realloc(pHeap, nMemThisDb);
       if( pHeap==0 ){
         fatalError("failed to allocate %d bytes of heap memory", nMem);
       }
       sqlite3_config(SQLITE_CONFIG_HEAP, pHeap, nMemThisDb, 128);
     }
+
+    /* Disable lookaside with the --native-malloc option */
+    if( nativeMalloc ){
+      sqlite3_config(SQLITE_CONFIG_LOOKASIDE, 0, 0);
+    }
   
     /* Reset the in-memory virtual filesystem */
     formatVfs();
     
     /* Run a test using each SQL script against each database.
@@ -1205,13 +1215,17 @@
 #endif
           do{
             runSql(db, (char*)pSql->a, runFlags);
           }while( timeoutTest );
           setAlarm(0);
+          sqlite3_exec(db, "PRAGMA temp_store_directory=''", 0, 0, 0);
           sqlite3_close(db);
         }
-        if( sqlite3_memory_used()>0 ) fatalError("memory leak");
+        if( sqlite3_memory_used()>0 ){
+           fatalError("memory leak: %lld bytes outstanding",
+                      sqlite3_memory_used());
+        }
         reformatVfs();
         nTest++;
         g.zTestName[0] = 0;
 
         /* Simulate an error if the TEST_FAILURE environment variable is "5".

Index: test/ossfuzz.c
==================================================================
--- test/ossfuzz.c
+++ test/ossfuzz.c
@@ -143,10 +143,11 @@
   }
 
   /* Cleanup and return */
   sqlite3_free(zErrMsg);
   sqlite3_free(zSql);
+  sqlite3_exec(cx.db, "PRAGMA temp_store_directory=''", 0, 0, 0);
   sqlite3_close(cx.db);
 
   if( mDebug & FUZZ_SHOW_MAX_DELAY ){
     printf("Progress callback count....... %d\n", cx.nCb);
     printf("Max time between callbacks.... %d ms\n", (int)cx.mxInterval);