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Tcl_BackgroundError(3)                     Tcl Library Procedures                     Tcl_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 identi-fying identifying
       fying  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
       bgerror  Tcl  command  to report the error in an application-specific fashion.  If no bgerror command
       exists, or if it returns with an error condition, then Tcl_BackgroundError reports the  error  itself
       by printing a message on the standard error file.

       Tcl_BackgroundError does not invoke bgerror immediately because this could potentially interfere with
       scripts that are in process at the time the error occurred.  Instead, it invokes bgerror later as  an
       idle  callback.   Tcl_BackgroundError  saves  the values of the errorInfo and errorCode variables and
       restores these values just before invoking bgerror.

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


KEYWORDS
       background, bgerror, error



Tcl                                                  7.5                              Tcl_BackgroundError(3)