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Tcl_Cancel(3) Tcl Library Procedures Tcl_Cancel(3)
Tcl_CancelEval, Tcl_Canceled - cancel Tcl scripts
Tcl_CancelEval(interp, resultObjPtr, clientData, flags)
Tcl_Interp *interp (in) Interpreter in which to cancel the
Tcl_Obj *resultObjPtr (in) Error message to use in the
cancellation, or NULL to use a default
message. If not NULL, this object will
have its reference count decremented
before Tcl_CancelEval returns.
int flags (in) ORed combination of flag bits that
specify additional options. For
Tcl_CancelEval, only TCL_CANCEL_UNWIND
is currently supported. For
Tcl_Canceled, only TCL_LEAVE_ERR_MSG
and TCL_CANCEL_UNWIND are currently
ClientData clientData (in) Currently reserved for future use. It
should be set to NULL.
Tcl_CancelEval cancels or unwinds the script in progress soon after the
next invocation of asynchronous handlers, causing TCL_ERROR to be the
return code for that script. This function is thread-safe and may be
called from any thread in the process.
Tcl_Canceled checks if the script in progress has been canceled and
returns TCL_ERROR if it has. Otherwise, TCL_OK is returned.
Extensions can use this function to check to see if they should abort a
long running command. This function is thread sensitive and may only
be called from the thread the interpreter was created in.
Any ORed combination of the following values may be used for the flags
argument to procedures such as Tcl_CancelEval:
TCL_CANCEL_UNWIND This flag is used by Tcl_CancelEval and
Tcl_Canceled. For Tcl_CancelEval, if this flag is
set, the script in progress is canceled and the
evaluation stack for the interpreter is unwound.
For Tcl_Canceled, if this flag is set, the script
in progress is considered to be canceled only if
the evaluation stack for the interpreter is being
TCL_LEAVE_ERR_MSG This flag is only used by Tcl_Canceled; it is
ignored by other procedures. If an error is
returned and this bit is set in flags, then an
error message will be left in the interpreter's
result, where it can be retrieved with
Tcl_GetObjResult or Tcl_GetStringResult. If this
flag bit is not set then no error message is left
and the interpreter's result will not be modified.
interp(n), Tcl_Eval(3), TIP 285
Tcl 8.6 Tcl_Cancel(3)