Index: ext/rbu/rbuvacuum.test
==================================================================
--- ext/rbu/rbuvacuum.test
+++ ext/rbu/rbuvacuum.test
@@ -15,19 +15,19 @@
 #
 
 source [file join [file dirname [info script]] rbu_common.tcl]
 set ::testprefix rbuvacuum
 
-proc do_rbu_vacuum_test {tn} {
+proc do_rbu_vacuum_test {tn step} {
   uplevel [list do_test $tn.1 {
     forcedelete state.db
-    if {$::step==0} { sqlite3rbu_vacuum rbu test.db state.db }
+    if {$step==0} { sqlite3rbu_vacuum rbu test.db state.db }
     while 1 {
-      if {$::step==1} { sqlite3rbu_vacuum rbu test.db state.db }
+      if {$step==1} { sqlite3rbu_vacuum rbu test.db state.db }
       set rc [rbu step]
       if {$rc!="SQLITE_OK"} break
-      if {$::step==1} { rbu close }
+      if {$step==1} { rbu close }
     }
     rbu close
   } {SQLITE_DONE}]
 
   uplevel [list do_execsql_test $tn.2 {
@@ -47,11 +47,11 @@
     INSERT INTO t1 VALUES(1, 2, 3);
     INSERT INTO t1 VALUES(4, 5, 6);
     INSERT INTO t1 VALUES(7, 8, 9);
     PRAGMA integrity_check;
   } {ok}
-  do_rbu_vacuum_test 1.1
+  do_rbu_vacuum_test 1.1 $step
 
   # A vacuum that actually reclaims space.
   do_execsql_test 1.2.1 {
     INSERT INTO t1 VALUES(8, randomblob(900), randomblob(900));
     INSERT INTO t1 VALUES(9, randomblob(900), randomblob(900));
@@ -62,11 +62,11 @@
   } {12}
   do_execsql_test 1.2.2 {
     DELETE FROM t1 WHERE rowid BETWEEN 8 AND 11;
     PRAGMA page_count;
   } {12}
-  do_rbu_vacuum_test 1.2.3
+  do_rbu_vacuum_test 1.2.3 $step
   do_execsql_test 1.2.4 {
     PRAGMA page_count;
   } {3}
   
   # Add an index to the table.
@@ -80,11 +80,11 @@
   } {18}
   do_execsql_test 1.3.2 {
     DELETE FROM t1 WHERE rowid BETWEEN 12 AND 15;
     PRAGMA page_count;
   } {18}
-  do_rbu_vacuum_test 1.3.3
+  do_rbu_vacuum_test 1.3.3 $step
   do_execsql_test 1.3.4 {
     PRAGMA page_count;
   } {5}
 
   # WITHOUT ROWID table.
@@ -100,11 +100,11 @@
     INSERT INTO t2 VALUES(randomblob(900), 8, randomblob(900));
 
     DELETE FROM t2 WHERE b BETWEEN 2 AND 7;
     PRAGMA page_count;
   } {20}
-  do_rbu_vacuum_test 1.4.2
+  do_rbu_vacuum_test 1.4.2 $step
   do_execsql_test 1.4.3 {
     PRAGMA page_count;
   } {10}
   
   # WITHOUT ROWID table with an index.
@@ -118,11 +118,11 @@
     INSERT INTO t2 VALUES(randomblob(900), 13, randomblob(900));
 
     DELETE FROM t2 WHERE b BETWEEN 8 AND 12;
     PRAGMA page_count;
   } {35}
-  do_rbu_vacuum_test 1.4.2
+  do_rbu_vacuum_test 1.4.2 $step
   do_execsql_test 1.4.3 {
     PRAGMA page_count;
   } {15}
   do_execsql_test 1.4.4 {
     VACUUM;
@@ -133,11 +133,11 @@
     CREATE TABLE t3(a, b, c);
     INSERT INTO t3 VALUES('a', 'b', 'c');
     INSERT INTO t3 VALUES('d', 'e', 'f');
     INSERT INTO t3 VALUES('g', 'h', 'i');
   }
-  do_rbu_vacuum_test 1.5.2
+  do_rbu_vacuum_test 1.5.2 $step
   do_execsql_test 1.5.3 {
     SELECT * FROM t3
   } {a b c d e f g h i}
   do_execsql_test 1.5.4 {
     CREATE INDEX t3a ON t3(a);
@@ -144,11 +144,11 @@
     CREATE INDEX t3b ON t3(b);
     CREATE INDEX t3c ON t3(c);
     INSERT INTO t3 VALUES('j', 'k', 'l');
     DELETE FROM t3 WHERE a = 'g';
   }
-  do_rbu_vacuum_test 1.5.5
+  do_rbu_vacuum_test 1.5.5 $step
   do_execsql_test 1.5.6 {
     SELECT rowid, * FROM t3 ORDER BY b
   } {1 a b c 2 d e f 4 j k l}
 
   do_execsql_test 1.6.1 {
@@ -155,11 +155,11 @@
     CREATE TABLE t4(a PRIMARY KEY, b, c);
     INSERT INTO t4 VALUES('a', 'b', 'c');
     INSERT INTO t4 VALUES('d', 'e', 'f');
     INSERT INTO t4 VALUES('g', 'h', 'i');
   }
-  do_rbu_vacuum_test 1.6.2
+  do_rbu_vacuum_test 1.6.2 $step
   do_execsql_test 1.6.3 {
     SELECT * FROM t4
   } {a b c d e f g h i}
   do_execsql_test 1.6.4 {
     CREATE INDEX t4a ON t4(a);
@@ -167,15 +167,71 @@
     CREATE INDEX t4c ON t4(c);
     
     INSERT INTO t4 VALUES('j', 'k', 'l');
     DELETE FROM t4 WHERE a='g';
   }
-  do_rbu_vacuum_test 1.6.5
+  do_rbu_vacuum_test 1.6.5 $step
   do_execsql_test 1.6.6 {
     SELECT * FROM t4 ORDER BY b
   } {a b c d e f j k l}
 
+}
+
+#-------------------------------------------------------------------------
+# Test some error cases:
+#
+#   2.1.* the db being vacuumed being in wal mode already.
+#   2.2.* database modified mid vacuum.
+#
+reset_db
+do_execsql_test 2.1.0 {
+  CREATE TABLE t1(a, b);
+  INSERT INTO t1 VALUES(1, 2);
+  INSERT INTO t1 VALUES(3, 4);
+  INSERT INTO t1 VALUES(5, 6);
+  INSERT INTO t1 VALUES(7, 8);
+  PRAGMA journal_mode = wal;
+  INSERT INTO t1 VALUES(9, 10);
+} wal
+do_test 2.1.1 {
+  forcedelete state.db
+  sqlite3rbu_vacuum rbu test.db state.db
+  rbu step
+} {SQLITE_ERROR}
+do_test 2.1.2 {
+  list [catch { rbu close } msg] $msg
+} {1 {SQLITE_ERROR - cannot vacuum wal mode database}}
+
+reset_db
+do_execsql_test 2.2.0 {
+  CREATE TABLE tx(a PRIMARY KEY, b BLOB);
+  INSERT INTO tx VALUES(1, randomblob(900));
+  INSERT INTO tx SELECT a+1, randomblob(900) FROM tx;
+  INSERT INTO tx SELECT a+2, randomblob(900) FROM tx;
+  INSERT INTO tx SELECT a+4, randomblob(900) FROM tx;
+  INSERT INTO tx SELECT a+8, randomblob(900) FROM tx;
+}
+db_save_and_close
+for {set i 1} 1 {incr i} {
+  forcedelete state.db
+  db_restore_and_reopen
+
+  sqlite3rbu_vacuum rbu test.db state.db
+  for {set step 0} {$step<$i} {incr step} { rbu step }
+  rbu close
+  if {[file exists test.db-wal]} break
+
+  execsql { INSERT INTO tx VALUES(20, 20) }
+
+  do_test 2.2.$i.1 {
+    sqlite3rbu_vacuum rbu test.db state.db 
+    rbu step
+  } {SQLITE_BUSY}
+  do_test 2.2.$i.2 {
+    list [catch { rbu close } msg] $msg
+  } {1 {SQLITE_BUSY - database modified during rbu vacuum}}
+
 }
 
 catch { db close }
 finish_test
 

Index: ext/rbu/sqlite3rbu.c
==================================================================
--- ext/rbu/sqlite3rbu.c
+++ ext/rbu/sqlite3rbu.c
@@ -397,11 +397,11 @@
   sqlite3rbu *pRbu;               /* Pointer to rbu object (rbu target only) */
 
   int openFlags;                  /* Flags this file was opened with */
   u32 iCookie;                    /* Cookie value for main db files */
   u8 iWriteVer;                   /* "write-version" value for main db files */
-  u8 bNolock;
+  u8 bNolock;                     /* True to fail EXCLUSIVE locks */
 
   int nShm;                       /* Number of entries in apShm[] array */
   char **apShm;                   /* Array of mmap'd *-shm regions */
   char *zDel;                     /* Delete this when closing file */
 
@@ -2371,13 +2371,16 @@
     }
     if( bOpen ) p->dbMain = rbuOpenDbhandle(p, p->zRbu, p->nRbu<=1);
   }
 
   p->eStage = 0;
-  if( p->dbMain==0 ){
+  if( p->rc==SQLITE_OK && p->dbMain==0 ){
     if( !rbuIsVacuum(p) ){
       p->dbMain = rbuOpenDbhandle(p, p->zTarget, 1);
+    }else if( p->pRbuFd->pWalFd ){
+      p->rc = SQLITE_ERROR;
+      p->zErrmsg = sqlite3_mprintf("cannot vacuum wal mode database");
     }else{
       char *zTarget = sqlite3_mprintf("file:%s-vacuum?rbu_memory=1", p->zRbu);
       if( zTarget==0 ){
         p->rc = SQLITE_NOMEM;
         return;
@@ -2985,10 +2988,11 @@
 ** are determined by inspecting the rbu handle passed as the first argument.
 */
 static void rbuSaveState(sqlite3rbu *p, int eStage){
   if( p->rc==SQLITE_OK || p->rc==SQLITE_DONE ){
     sqlite3_stmt *pInsert = 0;
+    rbu_file *pFd = (rbuIsVacuum(p) ? p->pRbuFd : p->pTargetFd);
     int rc;
 
     assert( p->zErrmsg==0 );
     rc = prepareFreeAndCollectError(p->dbRbu, &pInsert, &p->zErrmsg, 
         sqlite3_mprintf(
@@ -3007,11 +3011,11 @@
           RBU_STATE_TBL, p->objiter.zTbl, 
           RBU_STATE_IDX, p->objiter.zIdx, 
           RBU_STATE_ROW, p->nStep, 
           RBU_STATE_PROGRESS, p->nProgress,
           RBU_STATE_CKPT, p->iWalCksum,
-          RBU_STATE_COOKIE, (i64)p->pTargetFd->iCookie,
+          RBU_STATE_COOKIE, (i64)pFd->iCookie,
           RBU_STATE_OALSZ, p->iOalSz,
           RBU_STATE_PHASEONESTEP, p->nPhaseOneStep
       )
     );
     assert( pInsert==0 || rc==SQLITE_OK );
@@ -3429,21 +3433,25 @@
         p->eStage = RBU_STAGE_CKPT;
         p->nStep = 0;
       }
     }
 
-    if( p->rc==SQLITE_OK
-     && !rbuIsVacuum(p)
+    if( p->rc==SQLITE_OK 
      && (p->eStage==RBU_STAGE_OAL || p->eStage==RBU_STAGE_MOVE)
-     && pState->eStage!=0 && p->pTargetFd->iCookie!=pState->iCookie
-    ){   
-      /* At this point (pTargetFd->iCookie) contains the value of the
-      ** change-counter cookie (the thing that gets incremented when a 
-      ** transaction is committed in rollback mode) currently stored on 
-      ** page 1 of the database file. */
-      p->rc = SQLITE_BUSY;
-      p->zErrmsg = sqlite3_mprintf("database modified during rbu update");
+     && pState->eStage!=0
+    ){
+      rbu_file *pFd = (rbuIsVacuum(p) ? p->pRbuFd : p->pTargetFd);
+      if( pFd->iCookie!=pState->iCookie ){   
+        /* At this point (pTargetFd->iCookie) contains the value of the
+        ** change-counter cookie (the thing that gets incremented when a 
+        ** transaction is committed in rollback mode) currently stored on 
+        ** page 1 of the database file. */
+        p->rc = SQLITE_BUSY;
+        p->zErrmsg = sqlite3_mprintf("database modified during rbu %s",
+            (rbuIsVacuum(p) ? "vacuum" : "update")
+        );
+      }
     }
 
     if( p->rc==SQLITE_OK ){
       if( p->eStage==RBU_STAGE_OAL ){
         sqlite3 *db = p->dbMain;
@@ -3839,10 +3847,11 @@
           u8 *aBuf = (u8*)zBuf;
           rbuPutU32(&aBuf[52], 0);          /* largest root page number */
           rbuPutU32(&aBuf[36], 0);          /* number of free pages */
           rbuPutU32(&aBuf[32], 0);          /* first page on free list trunk */
           rbuPutU32(&aBuf[28], 1);          /* size of db file in pages */
+          rbuPutU32(&aBuf[24], pRbu->pRbuFd->iCookie+1);  /* Change counter */
 
           if( iAmt>100 ){
             assert( iAmt>=101 );
             memset(&aBuf[101], 0, iAmt-101);
             rbuPutU16(&aBuf[105], iAmt & 0xFFFF);
@@ -3855,17 +3864,10 @@
       /* These look like magic numbers. But they are stable, as they are part
        ** of the definition of the SQLite file format, which may not change. */
       u8 *pBuf = (u8*)zBuf;
       p->iCookie = rbuGetU32(&pBuf[24]);
       p->iWriteVer = pBuf[19];
-      if( pRbu && rbuIsVacuum(p->pRbu) ){
-        rbu_file *pRbuFd = 0;
-        sqlite3_file_control(pRbu->dbRbu, "main", 
-            SQLITE_FCNTL_FILE_POINTER, (void*)&pRbuFd
-        );
-        rbuPutU32(&pBuf[24], pRbuFd->iCookie+1);
-      }
     }
   }
   return rc;
 }