debugger {utils} | R Documentation |
Functions to dump the evaluation environments (frames) and to examine dumped frames.
dump.frames(dumpto = "last.dump", to.file = FALSE)
debugger(dump = last.dump)
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 |
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 (a 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.
Invisible NULL
.
Functions such as sys.parent
and
environment
applied to closures will not work correctly
inside debugger
.
If the error occurred when computing the default value of a formal argument the debugger will report "recursive default argument reference" when trying to examine that environment.
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.
Becker, R. A., Chambers, J. M. and Wilks, A. R. (1988) The New S Language. Wadsworth & Brooks/Cole.
options
for setting error
options;
recover
is an interactive debugger working similarly to
debugger
but directly after the error occurs.
## 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)