SQLite

  Tcl_Interp *interp;        /* The interpreter used for this database */
  char *zBusy;               /* The busy callback routine */
  char *zCommit;             /* The commit hook callback routine */
  char *zTrace;              /* The trace callback routine */
  char *zTraceV2;            /* The trace_v2 callback routine */
  char *zProfile;            /* The profile callback routine */
  char *zProgress;           /* The progress callback routine */
  char *zBindFallback;       /* Callback to invoke on a binding miss */
  char *zAuth;               /* The authorization callback routine */
  int disableAuth;           /* Disable the authorizer if it exists */
  char *zNull;               /* Text to substitute for an SQL NULL value */
  SqlFunc *pFunc;            /* List of SQL functions */
  Tcl_Obj *pUpdateHook;      /* Update hook script (if any) */
  Tcl_Obj *pPreUpdateHook;   /* Pre-update hook script (if any) */
  Tcl_Obj *pRollbackHook;    /* Rollback hook script (if any) */

  }
  if( pDb->zTraceV2 ){
    Tcl_Free(pDb->zTraceV2);
  }
  if( pDb->zProfile ){
    Tcl_Free(pDb->zProfile);
  }
  if( pDb->zBindFallback ){
    Tcl_Free(pDb->zBindFallback);
  }
  if( pDb->zAuth ){
    Tcl_Free(pDb->zAuth);
  }
  if( pDb->zNull ){
    Tcl_Free(pDb->zNull);
  }
  if( pDb->pUpdateHook ){

  sqlite3_stmt *pStmt = 0;        /* Prepared statement object */
  SqlPreparedStmt *pPreStmt;      /* Pointer to cached statement */
  int nSql;                       /* Length of zSql in bytes */
  int nVar = 0;                   /* Number of variables in statement */
  int iParm = 0;                  /* Next free entry in apParm */
  char c;
  int i;
  int needResultReset = 0;        /* Need to invoke Tcl_ResetResult() */
  int rc = SQLITE_OK;             /* Value to return */
  Tcl_Interp *interp = pDb->interp;

  *ppPreStmt = 0;

  /* Trim spaces from the start of zSql and calculate the remaining length. */
  while( (c = zSql[0])==' ' || c=='\t' || c=='\r' || c=='\n' ){ zSql++; }
  nSql = strlen30(zSql);

  assert( 0==memcmp(pPreStmt->zSql, zSql, pPreStmt->nSql) );

  /* Bind values to parameters that begin with $ or : */
  for(i=1; i<=nVar; i++){
    const char *zVar = sqlite3_bind_parameter_name(pStmt, i);
    if( zVar!=0 && (zVar[0]=='$' || zVar[0]==':' || zVar[0]=='@') ){
      Tcl_Obj *pVar = Tcl_GetVar2Ex(interp, &zVar[1], 0, 0);
      if( pVar==0 && pDb->zBindFallback!=0 ){
        Tcl_Obj *pCmd;
        int rx;
        pCmd = Tcl_NewStringObj(pDb->zBindFallback, -1);
        Tcl_IncrRefCount(pCmd);
        Tcl_ListObjAppendElement(interp, pCmd, Tcl_NewStringObj(zVar,-1));
        if( needResultReset ) Tcl_ResetResult(interp);
        needResultReset = 1;
        rx = Tcl_EvalObjEx(interp, pCmd, TCL_EVAL_DIRECT);
        Tcl_DecrRefCount(pCmd);
        if( rx==TCL_OK ){
          pVar = Tcl_GetObjResult(interp);
        }else if( rx==TCL_ERROR ){
          rc = TCL_ERROR;
          break;
        }else{
          pVar = 0;
        }
      }
      if( pVar ){
        int n;
        u8 *data;
        const char *zType = (pVar->typePtr ? pVar->typePtr->name : "");
        c = zType[0];
        if( zVar[0]=='@' ||
           (c=='b' && strcmp(zType,"bytearray")==0 && pVar->bytes==0) ){

          sqlite3_bind_text(pStmt, i, (char *)data, n, SQLITE_STATIC);
          Tcl_IncrRefCount(pVar);
          pPreStmt->apParm[iParm++] = pVar;
        }
      }else{
        sqlite3_bind_null(pStmt, i);
      }
      if( needResultReset ) Tcl_ResetResult(pDb->interp);
    }
  }
  pPreStmt->nParm = iParm;
  *ppPreStmt = pPreStmt;
  if( needResultReset && rc==TCL_OK ) Tcl_ResetResult(pDb->interp);

  return rc;
}

/*
** Release a statement reference obtained by calling dbPrepareAndBind().
** There should be exactly one call to this function for each call to
** dbPrepareAndBind().
**

  int objc,
  Tcl_Obj *const*objv
){
  SqliteDb *pDb = (SqliteDb*)cd;
  int choice;
  int rc = TCL_OK;
  static const char *DB_strs[] = {
    "authorizer",             "backup",                "bind_fallback",
    "busy",                   "cache",                 "changes",
    "close",                  "collate",               "collation_needed",
    "commit_hook",            "complete",              "copy",
    "deserialize",            "enable_load_extension", "errorcode",
    "eval",                   "exists",                "function",
    "incrblob",               "interrupt",             "last_insert_rowid",
    "nullvalue",              "onecolumn",             "preupdate",
    "profile",                "progress",              "rekey",
    "restore",                "rollback_hook",         "serialize",
    "status",                 "timeout",               "total_changes",
    "trace",                  "trace_v2",              "transaction",
    "unlock_notify",          "update_hook",           "version",
    "wal_hook",               0                        

  };
  enum DB_enum {
    DB_AUTHORIZER,            DB_BACKUP,               DB_BIND_FALLBACK,
    DB_BUSY,                  DB_CACHE,                DB_CHANGES,
    DB_CLOSE,                 DB_COLLATE,              DB_COLLATION_NEEDED,
    DB_COMMIT_HOOK,           DB_COMPLETE,             DB_COPY,
    DB_DESERIALIZE,           DB_ENABLE_LOAD_EXTENSION,DB_ERRORCODE,
    DB_EVAL,                  DB_EXISTS,               DB_FUNCTION,
    DB_INCRBLOB,              DB_INTERRUPT,            DB_LAST_INSERT_ROWID,
    DB_NULLVALUE,             DB_ONECOLUMN,            DB_PREUPDATE,
    DB_PROFILE,               DB_PROGRESS,             DB_REKEY,
    DB_RESTORE,               DB_ROLLBACK_HOOK,        DB_SERIALIZE,
    DB_STATUS,                DB_TIMEOUT,              DB_TOTAL_CHANGES,
    DB_TRACE,                 DB_TRACE_V2,             DB_TRANSACTION,
    DB_UNLOCK_NOTIFY,         DB_UPDATE_HOOK,          DB_VERSION,
    DB_WAL_HOOK             
  };
  /* don't leave trailing commas on DB_enum, it confuses the AIX xlc compiler */

  if( objc<2 ){
    Tcl_WrongNumArgs(interp, 1, objv, "SUBCOMMAND ...");
    return TCL_ERROR;
  }

      Tcl_AppendResult(interp, "backup failed: ",
           sqlite3_errmsg(pDest), (char*)0);
      rc = TCL_ERROR;
    }
    sqlite3_close(pDest);
    break;
  }

  /*    $db bind_fallback ?CALLBACK?
  **
  ** When resolving bind parameters in an SQL statement, if the parameter
  ** cannot be associated with a TCL variable then invoke CALLBACK with a
  ** single argument that is the name of the parameter and use the return
  ** value of the CALLBACK as the binding.  If CALLBACK returns something
  ** other than TCL_OK or TCL_ERROR then bind a NULL.
  **
  ** If CALLBACK is an empty string, then revert to the default behavior 
  ** which is to set the binding to NULL.
  **
  ** If CALLBACK returns an error, that causes the statement execution to
  ** abort.  Hence, to configure a connection so that it throws an error
  ** on an attempt to bind an unknown variable, do something like this:
  **
  **     proc bind_error {name} {error "no such variable: $name"}
  **     db bind_fallback bind_error
  */
  case DB_BIND_FALLBACK: {
    if( objc>3 ){
      Tcl_WrongNumArgs(interp, 2, objv, "?CALLBACK?");
      return TCL_ERROR;
    }else if( objc==2 ){
      if( pDb->zBindFallback ){
        Tcl_AppendResult(interp, pDb->zBindFallback, (char*)0);
      }
    }else{
      char *zCallback;
      int len;
      if( pDb->zBindFallback ){
        Tcl_Free(pDb->zBindFallback);
      }
      zCallback = Tcl_GetStringFromObj(objv[2], &len);
      if( zCallback && len>0 ){
        pDb->zBindFallback = Tcl_Alloc( len + 1 );
        memcpy(pDb->zBindFallback, zCallback, len+1);
      }else{
        pDb->zBindFallback = 0;
      }
    }
    break;
  }

  /*    $db busy ?CALLBACK?
  **
  ** Invoke the given callback if an SQL statement attempts to open
  ** a locked database file.
  */
  case DB_BUSY: {

  set v [catch {sqlite3} msg]
  regsub {really_sqlite3} $msg {sqlite3} msg
  lappend v $msg
} [list 1 "wrong # args: should be \"$r\""]
do_test tcl-1.2 {
  set v [catch {db bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be authorizer, backup, bind_fallback, busy, cache, changes, close, collate, collation_needed, commit_hook, complete, copy, deserialize, enable_load_extension, errorcode, eval, exists, function, incrblob, interrupt, last_insert_rowid, nullvalue, onecolumn, preupdate, profile, progress, rekey, restore, rollback_hook, serialize, status, timeout, total_changes, trace, trace_v2, transaction, unlock_notify, update_hook, version, or wal_hook}}
do_test tcl-1.2.1 {
  set v [catch {db cache bogus} msg]
  lappend v $msg
} {1 {bad option "bogus": must be flush or size}}
do_test tcl-1.2.2 {
  set v [catch {db cache} msg]
  lappend v $msg

  list [catch { db function xyz -return ret } msg] $msg
} {1 {option requires an argument: -return}}

do_test 17.6.3 {
  list [catch { db function xyz -n object ret } msg] $msg
} {1 {bad option "-n": must be -argcount, -deterministic or -returntype}}

# 2019-02-28: The "bind_fallback" command.
#
do_test 18.100 {
  unset -nocomplain bindings abc def ghi jkl mno e01 e02
  set bindings(abc) [expr {1+2}]
  set bindings(def) {hello}
  set bindings(ghi) [expr {3.1415926*1.0}]
  proc bind_callback {nm} {
    global bindings
    set n2 [string range $nm 1 end]
    if {[info exists bindings($n2)]} {
      return $bindings($n2)
    }
    if {[string match e* $n2]} {
      error "no such variable: $nm"
    }
    return -code return {}
  }
  db bind_fallback bind_callback
  db eval {SELECT $abc, typeof($abc), $def, typeof($def), $ghi, typeof($ghi)}
} {3 integer hello text 3.1415926 real}
do_test 18.110 {
  db eval {SELECT quote(@def), typeof(@def)}
} {X'68656C6C6F' blob}
do_execsql_test 18.120 {
  SELECT typeof($mno);
} {null}
do_catchsql_test 18.130 {
  SELECT $e01;
} {1 {no such variable: $e01}}
do_test 18.140 {
  db bind_fallback
} {bind_callback}
do_test 18.200 {
  db bind_fallback {}
  db eval {SELECT $abc, typeof($abc), $def, typeof($def), $ghi, typeof($ghi)}
} {{} null {} null {} null}
do_test 18.300 {
  unset -nocomplain bindings
  proc bind_callback {nm} {lappend ::bindings $nm}
  db bind_fallback bind_callback
  db eval {SELECT $abc, @def, $ghi(123), :mno}
  set bindings
} {{$abc} @def {$ghi(123)} :mno}
do_test 18.900 {
  set rc [catch {db bind_fallback a b} msg]
  lappend rc $msg
} {1 {wrong # args: should be "db bind_fallback ?CALLBACK?"}}
do_test 18.910 {
  db bind_fallback bind_fallback_does_not_exist
} {}
do_catchsql_test 19.911 {
  SELECT $abc, typeof($abc), $def, typeof($def), $ghi, typeof($ghi);
} {1 {invalid command name "bind_fallback_does_not_exist"}}
db bind_fallback {}

finish_test