Tcl_BackgroundError()

report Tcl error that occurred in background processing 

Tcl Library Procedures

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 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.

PORTABILITY

Windows 10. Windows Server 2016. Windows Server 2019. Windows 11. Windows Server 2022. Windows Server 2025.

AVAILABILITY

PTC MKS Toolkit for Professional Developers
PTC MKS Toolkit for Enterprise Developers
PTC MKS Toolkit for Enterprise Developers 64-Bit Edition

PTC MKS Toolkit 10.5 Documentation Build 40.