Index: src/attach.c
==================================================================
--- src/attach.c
+++ src/attach.c
@@ -95,11 +95,11 @@
     ** from sqlite3_deserialize() to close database db->init.iDb and
     ** reopen it as a MemDB */
     pVfs = sqlite3_vfs_find("memdb");
     if( pVfs==0 ) return;
     pNew = &db->aDb[db->init.iDb];
-    sqlite3BtreeClose(pNew->pBt);
+    if( pNew->pBt ) sqlite3BtreeClose(pNew->pBt);
     pNew->pBt = 0;
     pNew->pSchema = 0;
     rc = sqlite3BtreeOpen(pVfs, "x", db, &pNew->pBt, 0, SQLITE_OPEN_MAIN_DB);
   }else{
     /* This is a real ATTACH
@@ -230,10 +230,11 @@
   if( rc==SQLITE_OK ){
     sqlite3BtreeEnterAll(db);
     db->init.iDb = 0;
     rc = sqlite3Init(db, &zErrDyn);
     sqlite3BtreeLeaveAll(db);
+    assert( zErrDyn==0 || rc!=SQLITE_OK );
   }
 #ifdef SQLITE_USER_AUTHENTICATION
   if( rc==SQLITE_OK ){
     u8 newAuth = 0;
     rc = sqlite3UserAuthCheckLogin(db, zName, &newAuth);
@@ -240,26 +241,28 @@
     if( newAuth<db->auth.authLevel ){
       rc = SQLITE_AUTH_USER;
     }
   }
 #endif
-  if( rc && !REOPEN_AS_MEMDB(db) ){
-    int iDb = db->nDb - 1;
-    assert( iDb>=2 );
-    if( db->aDb[iDb].pBt ){
-      sqlite3BtreeClose(db->aDb[iDb].pBt);
-      db->aDb[iDb].pBt = 0;
-      db->aDb[iDb].pSchema = 0;
-    }
-    sqlite3ResetAllSchemasOfConnection(db);
-    db->nDb = iDb;
-    if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
-      sqlite3OomFault(db);
-      sqlite3DbFree(db, zErrDyn);
-      zErrDyn = sqlite3MPrintf(db, "out of memory");
-    }else if( zErrDyn==0 ){
-      zErrDyn = sqlite3MPrintf(db, "unable to open database: %s", zFile);
+  if( rc ){
+    if( !REOPEN_AS_MEMDB(db) ){
+      int iDb = db->nDb - 1;
+      assert( iDb>=2 );
+      if( db->aDb[iDb].pBt ){
+        sqlite3BtreeClose(db->aDb[iDb].pBt);
+        db->aDb[iDb].pBt = 0;
+        db->aDb[iDb].pSchema = 0;
+      }
+      sqlite3ResetAllSchemasOfConnection(db);
+      db->nDb = iDb;
+      if( rc==SQLITE_NOMEM || rc==SQLITE_IOERR_NOMEM ){
+        sqlite3OomFault(db);
+        sqlite3DbFree(db, zErrDyn);
+        zErrDyn = sqlite3MPrintf(db, "out of memory");
+      }else if( zErrDyn==0 ){
+        zErrDyn = sqlite3MPrintf(db, "unable to open database: %s", zFile);
+      }
     }
     goto attach_error;
   }
   
   return;

Index: src/memdb.c
==================================================================
--- src/memdb.c
+++ src/memdb.c
@@ -470,31 +470,35 @@
   szPage = sqlite3BtreeGetPageSize(pBt);
   zSql = sqlite3_mprintf("PRAGMA \"%w\".page_count", zSchema);
   rc = zSql ? sqlite3_prepare_v2(db, zSql, -1, &pStmt, 0) : SQLITE_NOMEM;
   sqlite3_free(zSql);
   if( rc ) return 0;
-  sqlite3_step(pStmt);
-  sz = sqlite3_column_int64(pStmt, 0)*szPage;
-  if( piSize ) *piSize = sz;
-  if( mFlags & SQLITE_SERIALIZE_NOCOPY ){
+  rc = sqlite3_step(pStmt);
+  if( rc!=SQLITE_ROW ){
     pOut = 0;
   }else{
-    pOut = sqlite3_malloc64( sz );
-    if( pOut ){
-      int nPage = sqlite3_column_int(pStmt, 0);
-      Pager *pPager = sqlite3BtreePager(pBt);
-      int pgno;
-      for(pgno=1; pgno<=nPage; pgno++){
-        DbPage *pPage = 0;
-        unsigned char *pTo = pOut + szPage*(sqlite3_int64)(pgno-1);
-        rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pPage, 0);
-        if( rc==SQLITE_OK ){
-          memcpy(pTo, sqlite3PagerGetData(pPage), szPage);
-        }else{
-          memset(pTo, 0, szPage);
-        }
-        sqlite3PagerUnref(pPage);       
+    sz = sqlite3_column_int64(pStmt, 0)*szPage;
+    if( piSize ) *piSize = sz;
+    if( mFlags & SQLITE_SERIALIZE_NOCOPY ){
+      pOut = 0;
+    }else{
+      pOut = sqlite3_malloc64( sz );
+      if( pOut ){
+        int nPage = sqlite3_column_int(pStmt, 0);
+        Pager *pPager = sqlite3BtreePager(pBt);
+        int pgno;
+        for(pgno=1; pgno<=nPage; pgno++){
+          DbPage *pPage = 0;
+          unsigned char *pTo = pOut + szPage*(sqlite3_int64)(pgno-1);
+          rc = sqlite3PagerGet(pPager, pgno, (DbPage**)&pPage, 0);
+          if( rc==SQLITE_OK ){
+            memcpy(pTo, sqlite3PagerGetData(pPage), szPage);
+          }else{
+            memset(pTo, 0, szPage);
+          }
+          sqlite3PagerUnref(pPage);       
+        }
       }
     }
   }
   sqlite3_finalize(pStmt);
   return pOut;
@@ -534,19 +538,20 @@
   if( rc!=SQLITE_DONE ){
     rc = SQLITE_ERROR;
     goto end_deserialize;
   }
   p = memdbFromDbSchema(db, zSchema);
-  /* The memdbFromDbSchema() call can only fail if zSchema is not
-  ** a valid schema name or if the schema is not a memdb schema.  But
-  ** neither of those things can be true here, so failure is not possible */
-  assert( p!=0 );
-  p->aData = pData;
-  p->sz = szDb;
-  p->szMax = szBuf;
-  p->mFlags = mFlags;
-  rc = SQLITE_OK;
+  if( p==0 ){
+    rc = SQLITE_ERROR;
+  }else{
+    p->aData = pData;
+    p->sz = szDb;
+    p->szMax = szBuf;
+    p->mFlags = mFlags;
+    rc = SQLITE_OK;
+  }
+
 end_deserialize:
   sqlite3_finalize(pStmt);
   sqlite3_mutex_leave(db->mutex);
   return rc;
 }