Tcl_BackgroundError(3tcl)

Tcl_BackgroundError(3)Tcl Library ProcedureTcl_BackgroundError(3)

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NAME

     Tcl_BackgroundError - report  Tcl  error  that  occurred  in
     background processing

SYNOPSIS

     #include <tcl.h>

     Tcl_BackgroundError(interp)

ARGUMENTS

     Tcl_Interp *interp (in)          Interpreter  in  which  the
                                      error occurred.
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DESCRIPTION

     This procedure is typically invoked when a Tcl error  occurs
     during  "background  processing"  such as executing an event
     handler.  When such an error occurs, the error condition  is
     reported  to  Tcl  or  to a widget or some other C code, and
     there is not usually any obvious way for that code to report
     the  error  to  the  user.   In  these  cases the code calls
     Tcl_BackgroundError with an interp argument identifying  the
     interpreter  in  which  the  error  occurred.   At  the time
     Tcl_BackgroundError is invoked, the interpreter's result  is
     expected  to  contain an error message.  Tcl_BackgroundError
     will invoke the command registered in  that  interpreter  to
     handle background errors by the interp bgerror command.  The
     registered handler command is meant to report the  error  in
     an   application-specific   fashion.   The  handler  command
     receives two arguments, the result of the  interp,  and  the
     return options of the interp at the time the error occurred.
     If the application registers no handler command, the default
     handler  command  will attempt to call bgerror to report the
     error.  If an error  condition  arises  while  invoking  the
     handler  command, then Tcl_BackgroundError reports the error
     itself by printing a message on the standard error file.

     Tcl_BackgroundError does  not  invoke  the  handler  command
     immediately  because  this  could potentially interfere with
     scripts that are in process at the time the error  occurred.
     Instead,  it  invokes  the  handler command later as an idle
     callback.

     It is possible for  many  background  errors  to  accumulate
     before  the  handler command is invoked.  When this happens,
     each of the errors is processed in order.  However,  if  the
     handle command returns a break exception, then all remaining
     error reports for the interpreter are skipped.

Tcl                     Last change: 7.5                        1

Tcl_BackgroundError(3)Tcl Library ProcedureTcl_BackgroundError(3)

KEYWORDS

     background, bgerror, error, interp

Tcl                     Last change: 7.5                        2