Index: ext/fts3/fts3.c
==================================================================
--- ext/fts3/fts3.c
+++ ext/fts3/fts3.c
@@ -969,11 +969,12 @@
   sqlite3 *db,                    /* Database handle */
   const char *zDb,                /* Name of db (i.e. "main", "temp" etc.) */
   const char *zTbl,               /* Name of content table */
   const char ***pazCol,           /* OUT: Malloc'd array of column names */
   int *pnCol,                     /* OUT: Size of array *pazCol */
-  int *pnStr                      /* OUT: Bytes of string content */
+  int *pnStr,                     /* OUT: Bytes of string content */
+  char **pzErr                    /* OUT: error message */
 ){
   int rc = SQLITE_OK;             /* Return code */
   char *zSql;                     /* "SELECT *" statement on zTbl */  
   sqlite3_stmt *pStmt = 0;        /* Compiled version of zSql */
 
@@ -980,10 +981,13 @@
   zSql = sqlite3_mprintf("SELECT * FROM %Q.%Q", zDb, zTbl);
   if( !zSql ){
     rc = SQLITE_NOMEM;
   }else{
     rc = sqlite3_prepare(db, zSql, -1, &pStmt, 0);
+    if( rc!=SQLITE_OK ){
+      *pzErr = sqlite3_mprintf("%s", sqlite3_errmsg(db));
+    }
   }
   sqlite3_free(zSql);
 
   if( rc==SQLITE_OK ){
     const char **azCol;           /* Output array */
@@ -1213,11 +1217,11 @@
     zCompress = 0;
     zUncompress = 0;
     if( nCol==0 ){
       sqlite3_free((void*)aCol); 
       aCol = 0;
-      rc = fts3ContentColumns(db, argv[1], zContent, &aCol, &nCol, &nString);
+      rc = fts3ContentColumns(db, argv[1], zContent,&aCol,&nCol,&nString,pzErr);
 
       /* If a languageid= option was specified, remove the language id
       ** column from the aCol[] array. */ 
       if( rc==SQLITE_OK && zLanguageid ){
         int j;

Index: src/vtab.c
==================================================================
--- src/vtab.c
+++ src/vtab.c
@@ -22,10 +22,12 @@
 ** are invoked only from within xCreate and xConnect methods.
 */
 struct VtabCtx {
   Table *pTab;
   VTable *pVTable;
+  VtabCtx *pPrior;    /* Parent context (if any) */
+  int bDeclared;      /* True after sqlite3_declare_vtab() is called */
 };
 
 /*
 ** The actual function that does the work of creating a new module.
 ** This function implements the sqlite3_create_module() and
@@ -451,12 +453,24 @@
   VTable *pVTable;
   int rc;
   const char *const*azArg = (const char *const*)pTab->azModuleArg;
   int nArg = pTab->nModuleArg;
   char *zErr = 0;
-  char *zModuleName = sqlite3MPrintf(db, "%s", pTab->zName);
+  char *zModuleName;
+  VtabCtx *pCtx;
+
+  /* Check that the virtual-table is not already being initialized */
+  for(pCtx=db->pVtabCtx; pCtx; pCtx=pCtx->pPrior){
+    if( pCtx->pTab==pTab ){
+      *pzErr = sqlite3MPrintf(db, 
+          "vtable constructor called recursively: %s", pTab->zName
+      );
+      return SQLITE_LOCKED;
+    }
+  }
 
+  zModuleName = sqlite3MPrintf(db, "%s", pTab->zName);
   if( !zModuleName ){
     return SQLITE_NOMEM;
   }
 
   pVTable = sqlite3DbMallocZero(db, sizeof(VTable));
@@ -470,14 +484,17 @@
   /* Invoke the virtual table constructor */
   assert( &db->pVtabCtx );
   assert( xConstruct );
   sCtx.pTab = pTab;
   sCtx.pVTable = pVTable;
+  sCtx.pPrior = db->pVtabCtx;
+  sCtx.bDeclared = 0;
   db->pVtabCtx = &sCtx;
   rc = xConstruct(db, pMod->pAux, nArg, azArg, &pVTable->pVtab, &zErr);
-  db->pVtabCtx = 0;
+  db->pVtabCtx = sCtx.pPrior;
   if( rc==SQLITE_NOMEM ) db->mallocFailed = 1;
+  assert( sCtx.pTab==pTab );
 
   if( SQLITE_OK!=rc ){
     if( zErr==0 ){
       *pzErr = sqlite3MPrintf(db, "vtable constructor failed: %s", zModuleName);
     }else {
@@ -488,11 +505,11 @@
   }else if( ALWAYS(pVTable->pVtab) ){
     /* Justification of ALWAYS():  A correct vtab constructor must allocate
     ** the sqlite3_vtab object if successful.  */
     pVTable->pVtab->pModule = pMod->pModule;
     pVTable->nRef = 1;
-    if( sCtx.pTab ){
+    if( sCtx.bDeclared==0 ){
       const char *zFormat = "vtable constructor did not declare schema: %s";
       *pzErr = sqlite3MPrintf(db, zFormat, pTab->zName);
       sqlite3VtabUnlock(pVTable);
       rc = SQLITE_ERROR;
     }else{
@@ -658,22 +675,23 @@
 ** This function is used to set the schema of a virtual table.  It is only
 ** valid to call this function from within the xCreate() or xConnect() of a
 ** virtual table module.
 */
 int sqlite3_declare_vtab(sqlite3 *db, const char *zCreateTable){
+  VtabCtx *pCtx = db->pVtabCtx;
   Parse *pParse;
-
   int rc = SQLITE_OK;
   Table *pTab;
   char *zErr = 0;
 
   sqlite3_mutex_enter(db->mutex);
-  if( !db->pVtabCtx || !(pTab = db->pVtabCtx->pTab) ){
+  if( !pCtx || pCtx->bDeclared ){
     sqlite3Error(db, SQLITE_MISUSE, 0);
     sqlite3_mutex_leave(db->mutex);
     return SQLITE_MISUSE_BKPT;
   }
+  pTab = pCtx->pTab;
   assert( (pTab->tabFlags & TF_Virtual)!=0 );
 
   pParse = sqlite3StackAllocZero(db, sizeof(*pParse));
   if( pParse==0 ){
     rc = SQLITE_NOMEM;
@@ -692,11 +710,11 @@
         pTab->aCol = pParse->pNewTable->aCol;
         pTab->nCol = pParse->pNewTable->nCol;
         pParse->pNewTable->nCol = 0;
         pParse->pNewTable->aCol = 0;
       }
-      db->pVtabCtx->pTab = 0;
+      pCtx->bDeclared = 1;
     }else{
       sqlite3Error(db, SQLITE_ERROR, (zErr ? "%s" : 0), zErr);
       sqlite3DbFree(db, zErr);
       rc = SQLITE_ERROR;
     }

Index: test/fts4content.test
==================================================================
--- test/fts4content.test
+++ test/fts4content.test
@@ -44,10 +44,13 @@
 #         SELECT statements.
 #
 #   8.* - Test that if the content=xxx and prefix options are used together,
 #         the 'rebuild' command still works.
 #
+#   11.* - Test that circular references (e.g. "t1(content=t1)") are
+#          detected.
+#
 
 do_execsql_test 1.1.1 {
   CREATE TABLE t1(a, b, c);
   INSERT INTO t1 VALUES('w x', 'x y', 'y z');
   CREATE VIRTUAL TABLE ft1 USING fts4(content=t1);
@@ -402,11 +405,11 @@
 #-------------------------------------------------------------------------
 # Test cases 6.* test 
 # 
 do_catchsql_test 6.1.1 {
   CREATE VIRTUAL TABLE ft7 USING fts4(content=t7);
-} {1 {vtable constructor failed: ft7}}
+} {1 {no such table: main.t7}}
 
 do_execsql_test 6.2.1 {
   CREATE TABLE t7(one, two);
   CREATE VIRTUAL TABLE ft7 USING fts4(content=t7);
   INSERT INTO t7 VALUES('A B', 'B A');
@@ -429,11 +432,11 @@
   ft7 ft7_segments ft7_segdir sqlite_autoindex_ft7_segdir_1 
   ft7_docsize ft7_stat
 }
 do_catchsql_test 6.2.4 {
   SELECT * FROM ft7;
-} {1 {vtable constructor failed: ft7}}
+} {1 {no such table: main.t7}}
 do_execsql_test 6.2.5 {
   CREATE TABLE t7(x, y);
   INSERT INTO t7 VALUES('A B', 'B A');
   INSERT INTO t7 VALUES('C D', 'A A');
   SELECT * FROM ft7;
@@ -519,7 +522,52 @@
 do_execsql_test 8.2 { SELECT * FROM ft10 WHERE a MATCH 'ab*';          }
 do_execsql_test 8.3 { INSERT INTO ft10(ft10) VALUES('rebuild');        }
 do_execsql_test 8.4 { SELECT rowid FROM ft10 WHERE a MATCH 'ab*';      } {1 2 3}
 do_execsql_test 8.5 { SELECT rowid FROM ft10 WHERE b MATCH 'abav*';    } {3}
 do_execsql_test 8.6 { SELECT rowid FROM ft10 WHERE ft10 MATCH 'abas*'; } {1}
+
+#-------------------------------------------------------------------------
+# Test cases 9.*
+# 
+reset_db
+register_echo_module [sqlite3_connection_pointer db]
+
+do_execsql_test 9.1 {
+  CREATE TABLE tbl1(a, b);
+  INSERT INTO tbl1 VALUES('a b', 'c d');
+  INSERT INTO tbl1 VALUES('e f', 'a b');
+  CREATE VIRTUAL TABLE e1 USING echo(tbl1);
+  CREATE VIRTUAL TABLE ft1 USING fts4(content=e1);
+  INSERT INTO ft1(ft1) VALUES('rebuild');
+}
+
+do_execsql_test 9.2 {
+  SELECT rowid, * FROM ft1 WHERE ft1 MATCH 'e'
+} {2 {e f} {a b}}
+
+do_execsql_test 9.3 {
+  SELECT rowid, * FROM ft1 WHERE ft1 MATCH 'a'
+} {1 {a b} {c d} 2 {e f} {a b}}
+
+do_execsql_test 9.4 { 
+  DELETE FROM ft1 WHERE docid=1;
+}
+
+do_execsql_test 9.5 {
+  SELECT rowid, * FROM ft1 WHERE ft1 MATCH 'a'
+} {2 {e f} {a b}}
+
+do_execsql_test 9.6 {
+  INSERT INTO ft1(ft1) VALUES('rebuild');
+  SELECT rowid, * FROM ft1 WHERE ft1 MATCH 'a'
+} {1 {a b} {c d} 2 {e f} {a b}}
+
+#-------------------------------------------------------------------------
+# Test cases 11.*
+# 
+reset_db
+
+do_catchsql_test 11.1 {
+  CREATE VIRTUAL TABLE x1 USING fts4(content=x1);
+} {1 {vtable constructor called recursively: x1}}
 
 finish_test