I've just added a couple of functions to R-devel to help with debugging. findLineNum() finds which line of which function corresponds to a particular line of source code; setBreakpoint() takes the output of findLineNum, and calls trace() to set a breakpoint there.

These rely on having source reference debug information in the code. This is the default for code read by source(), but not for packages. To get the source references in package code, set the environment variable R_KEEP_PKG_SOURCE=yes, or within R, set options(keep.source.pkgs=TRUE), then install the package from source code. Read ?findLineNum for details on how to tell it to search within packages, rather than limiting the search to the global environment.

For example,

x <- " f <- function(a, b) {
            if (a > b)  {
            } else {

eval(parse(text=x))  # Normally you'd use source() to read a file...

findLineNum("<text>#3")   # <text> is a dummy filename used by parse(text=)

This will print

f step 2,3,2 in <environment: R_GlobalEnv>

and you can use


to set a breakpoint there.
There are still some limitations (and probably bugs) in the code; I'll be fixing those over the next while.
Duncan Murdoch

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