R: Post-Mortem Debugging

debugger {base}

R Documentation

Post-Mortem Debugging

Description

Functions to dump the evaluation environments (frames) and to examine dumped frames.

Usage

dump.frames(dumpto = "last.dump", to.file = FALSE)
debugger(dump = last.dump)

Arguments

dumpto

a character string. The name of the object or file to dump to.

to.file

logical. Should the dump be to an R object or to a file?

dump

An R dump object created by dump.frames

Details

To use post-mortem debugging, set the option error to be a call to dump.frames. By default this dumps to an R object "last.dump" in the workspace, but it can be set to dump to a file (as dump of the object produced by a call to save). The dumped object contain the call stack, the active environments and the last error message as returned by geterrmessage.

When dumping to file, dumpto gives the name of the dumped object and the file name has .rda appended.

A dump object of class "dump.frames" can be examined by calling debugger. This will give the error message and a list of environments from which to select repeatedly. When an environment is selected, it is copied and the browser called from within the copy.

If dump.frames is installed as the error handler, execution will continue even in non-interactive sessions. See the examples for how to dump and then quit.

Value

None.

Note

Functions such as sys.parent and environment applied to closures will not work correctly inside debugger.

Of course post-mortem debugging will not work if R is too damaged to produce and save the dump, for example if it has run out of workspace.

options for setting error options.

## Not run: options(error=quote(dump.frames("testdump", TRUE))) f <- function() { g <- function() stop("test dump.frames") g() } f() # will generate a dump on file "testdump.rda" options(error=NULL) ## possibly in another R session load("testdump.rda") debugger(testdump) Available environments had calls: 1: f() 2: g() 3: stop("test dump.frames") Enter an environment number, or 0 to exit Selection: 1 Browsing in the environment with call: f() Called from: debugger.look(ind) Browse[1]> ls() [1] "g" Browse[1]> g function() stop("test dump.frames") <environment: 759818> Browse[1]> Available environments had calls: 1: f() 2: g() 3: stop("test dump.frames") Enter an environment number, or 0 to exit Selection: 0 ## A possible setting for non-interactive sessions options(error=quote({dump.frames(to.file=TRUE); q()})) ## End(Not run)

utilities error

Author(s)

B. D. Ripley

[Package base version 1.1 ]