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Tcl_Cancel(3tcl) Tcl Library Procedures Tcl_Cancel(3tcl) 





NAME


Tcl_CancelEval, Tcl_Canceled - cancel Tcl scripts






SYNOPSIS


#include <tcl.h>
int
Tcl_CancelEval(interp, resultObjPtr, clientData, flags)

int
Tcl_Canceled(interp, flags)






ARGUMENTS



  
Tcl_Interp *interp (in)

  
Interpreter in which to cancel the script.

  
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)

  
OR'ed 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 supported.

  
void *clientData (in)

  
Currently reserved for future use. It should be set to NULL.
    
    

    

  








DESCRIPTION


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.




FLAG BITS


Any OR'ed combination of the following values may be used for the
    flags argument to procedures such as Tcl_CancelEval:



  

  
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 unwound.

  

  
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.










REFERENCE COUNT MANAGEMENT


Tcl_CancelEval always decrements the reference count of its
    resultObjPtr argument (if that is non-NULL). It is expected to be
    usually called with an object with zero reference count. If the object is
    shared with some other location (including the Tcl evaluation stack) it
    should have its reference count incremented before calling this
  function.






SEE ALSO


interp(3tcl), Tcl_Eval(3tcl), TIP 285






KEYWORDS


cancel, unwind







  

    8.6
    Tcl