Profiling an installed R package with source line numbers?

Question

I'd like to profile functions in an installed R package (data.table) using Rprof() with line.profiling=TRUE. Normally, installed package are byte compiled, and line numbers are not available for byte compiled packages. The usual instructions for line profiling with Rprof() require using source() or eval(parse()) so that srcref attributes are present.

How can I load data.table so that line numbers are active? My naive attempts to first load the package with library(data.table) and then source('data.table.R') fails because some of the compiled C functions are not found when I attempt to use the package, presumably because library() is using a different namespace. Maybe there is some way to source() into the correct namespace?

Alternatively, perhaps I can build a modified version of data.table that is not byte compiled, and then load that in a way that keeps line numbers? What alterations would I have to make, and how would I then load it? I started by setting ByteCompile: FALSE and then trying R CMD INSTALL -l ~/R/lib --build data.table, but this still seems to be byte compiled.

I'm eager to make this work and will pursue any suggestions. I'm running R 3.2.1 on Linux, have full control over the machine, and can install anything else that is required.

Edit:

A more complete description of the problem I was trying to solve (and the solution for it) is here: https://github.com/Rdatatable/data.table/issues/1249

I ended up doing essentially what Joshua suggested: recompile the package with "KeepSource: TRUE" in the DESCRIPTION. For my purposes, I also found "ByteCompile: FALSE" to be helpful, although this might not apply generally. I also changed the version number so I could see that I was using my modified version.

Then I installed to a different location with "R CMD INSTALL data.table -l ~/R/lib", and loaded with "library(data.table, lib='~/R/lib')". When used with the patches given in the link, I got the line numbers of the allocations as I desired. But if anyone knows a solution that doesn't require recompilation, I'm sure that others would appreciate if you shared.

Answer 1

You should be able to get line numbers even if the package is byte-compiled. But, as it says in ?Rprof (emphasis added):

Individual statements will be recorded in the profile log if line.profiling is TRUE, and if the code being executed was parsed with source references. See parse for a discussion of source references. By default the statement locations are not shown in summaryRprof, but see that help page for options to enable the display.

That means you need to set KeepSource: TRUE either in the DESCRIPTION file or via the --with-keep.source argument to R CMD INSTALL.