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.
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.
KEYWORDS¶
background, bgerror, error, interp