[R] How to detach binary objects/libraries?

ripley@stats.ox.ac.uk ripley at stats.ox.ac.uk
Tue Mar 26 09:36:27 CET 2002

On 26 Mar 2002, Peter Dalgaard BSA wrote:

> Prof Brian D Ripley <ripley at stats.ox.ac.uk> writes:
> > But my point was: what does changing the file copy of an already loaded
> > shared library do?   It's not allowed on Windows, and on Solaris it will
> > lead to a crash.  I don't know about Linux, as I would never try it
> > given my experience.
> AFAIR, it works on Linux. Running processes just continue using the
> old version (which gets unlinked in the usual Unix way and goes away
> when no more processes are using it). E.g., you can upgrade the
> readline library without crashing all running instances of bash...

bash is using a static readline.  E.g. RH7.2:

gannet% ldd /bin/bash
        libtermcap.so.2 => /lib/libtermcap.so.2 (0x4002e000)
        libdl.so.2 => /lib/libdl.so.2 (0x40032000)
        libc.so.6 => /lib/i686/libc.so.6 (0x40036000)
        /lib/ld-linux.so.2 => /lib/ld-linux.so.2 (0x40000000)

More importantly it's not the same issue.  That would have been linking
against a shared library which the OS loads, and R is itself loading a
module which happens to be a shared library.  On MacOS X those are
different concepts.  As I understand it Linux's ld.so is not able to
update in-use shared libraries: it relies on a change in version number.

Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272860 (secr)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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