Tcl_BackgroundError(3) Tcl Library Procedures Tcl_BackgroundError(3)
NAME
Tcl_BackgroundError - report Tcl error that occurred in background pro-
cessing
SYNOPSIS
#include <tcl.h>
Tcl_BackgroundError(interp)
ARGUMENTS
Interpreter in which the error occurred.
DESCRIPTION
This procedure is typically invoked when a Tcl error occurs during 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 inter-
preter's result is expected to contain an error message. Tcl_Back-
groundError 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 han-
dler command later as an idle callback.
It is possible for many background errors to accumulate before the han-
dler command is invoked. When this happens, each of the errors is pro-
cessed in order. However, if the handle command returns a break excep-
tion, then all remaining error reports for the interpreter are skipped.
KEYWORDS
background, bgerror, error, interp
Tcl 7.5 Tcl_BackgroundError(3)
BackgdErr 8.5.4 - Generated Sun Aug 17 16:14:48 CDT 2008