reload(): Unload dynamic libraries

[wch]

Presently, to unload and reload a compiled library during development, you can do this:

library.dynam.unload('c_test', '~/R-dev/c_test/')
install()

test_func()

It would be good to automate the unloading process by making reload() automatically do it. The dynLibs() function might be helpful for finding the path of the loaded library.

This should also be tested on Windows and Linux. According to ?dyn.load, unloading won't work on Solaris.

[wch]

Normally, the dynamic library has the same name as the package, so this should work:

pkgname <- 'c_test'
pkgpath <- system.file(package=pkgname)
library.dynam.unload(pkgname, pkgpath)

But in case there are multiple libraries in that path, it might be better to search the .dynLibs() for all libraries that contain the pkgpath:

dynlib_paths <- vapply(.dynLibs(), function(x) x[["path"]], character(1))

# List all the libraries under that path
# Need to be careful since the string matches anywhere, not just at the beginning
dynlib_paths[grepl(pkgpath, dynlib_paths, fixed=TRUE)]

It appears that most packages have library files with the same name as the package. But there are some exceptions. A find in my library path turns up a few:

./data.table/libs/x86_64/datatable.so
./data.table/libs/x86_64/datatable.so.dSYM/Contents/Resources/DWARF/datatable.so
./rgl/libs/i386/aglrgl.so
./rgl/libs/i386/aglrgl.so.dSYM/Contents/Resources/DWARF/aglrgl.so
./rgl/libs/i386/rgl.so
./rgl/libs/i386/rgl.so.dSYM/Contents/Resources/DWARF/rgl.so
./rgl/libs/x86_64/aglrgl.so
./rgl/libs/x86_64/aglrgl.so.dSYM/Contents/Resources/DWARF/aglrgl.so
./rgl/libs/x86_64/rgl.so
./rgl/libs/x86_64/rgl.so.dSYM/Contents/Resources/DWARF/rgl.so

[wch]

This code should unload all the loaded libraries from a given package:

library(bitops)
# Show what's loaded
.dynLibs()

pkgname <- 'bitops'
# Get installation path for the package
pkgpath <- system.file(package=pkgname)

# Get a vector of paths for all loaded libs
dynlib_paths <- vapply(.dynLibs(), function(x) x[["path"]], character(1))

# Find which of the lib paths start with pkgpath
pkgmatch <- pkgpath == substr(dynlib_paths, 1, nchar(pkgpath))

# Get matching lib paths and strip off leading path and extension (.so or .dll)
libnames <- sub("\\.[^\\.]*$", "", basename(dynlib_paths[pkgmatch]))

library.dynam.unload(libnames, pkgpath)

# Show what's loaded
.dynLibs()

# We can also unload the package
detach(paste("package", pkgname, sep =":"), character.only = TRUE, force = TRUE, unload = TRUE)

I tried experimenting with plyr, but it appears that it can't be unloaded because devtools depends on testthat, which depends on stringr, which depends on plyr.

Also, it appears that some packages are nice enough to have an .onUnload function that does it automatically:

> MASS:::.onUnload
function (libpath) 
library.dynam.unload("MASS", libpath)
<environment: namespace:MASS>

[wch]

Implemented in #137.