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Tcl_BackgroundError(3) Tcl Library Procedures Tcl_BackgroundError(3)
Tcl_BackgroundError - report Tcl error that occurred in background processing
Tcl_Interp *interp (in) Interpreter in which the error occurred.
This procedure is typically invoked when a Tcl error occurs during ``background process-
ing'' 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 obvi-
ous 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 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 happens, 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.
background, bgerror, error
Tcl 7.5 Tcl_BackgroundError(3)
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