R devel - Sep 1999 - sys.on.exit appears non-functional (PR#269)

As far as I can see sys.on.exit() does not work. The following
will give a non-null result in S, and seems about the simplest possible
usage.

test <- function() {
  on.exit(print(1))
  ex <- sys.on.exit()
  str(ex)
  cat("exiting...\n")
}
> test()
 NULL
exiting...
[1] 1

Looking at the code suggests that on.exit is installing the code in
a different context from the one sys.on.exit is looking in, but this is
daunting for non-experts.

The help page does not say what this is supposed to do, of course, but
I assume it is intended to retrieve the on.exit expression, as in S.

--please do not edit the information below--

Version:
 platform = sparc-sun-solaris2.6
 arch = sparc
 os = solaris2.6
 system = sparc, solaris2.6
 status = 
 status.rev = 0
 major = 0
 minor = 65.0
 year = 1999
 month = August
 day = 27
 language = R

Search Path:
 .GlobalEnv, Autoloads, package:base


-- 
Brian D. Ripley,                  ripley@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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ripley@stats.ox.ac.uk writes:
> As far as I can see sys.on.exit() does not work. The following
> will give a non-null result in S, and seems about the simplest possible
> usage.
> 
> test <- function() {
>   on.exit(print(1))
>   ex <- sys.on.exit()
>   str(ex)
>   cat("exiting...\n")
> }
> > test()
>  NULL
> exiting...
> [1] 1
> 
> Looking at the code suggests that on.exit is installing the code in
> a different context from the one sys.on.exit is looking in, but this is
> daunting for non-experts.
Not really that hard, once I realised that R_GlobalContext is not a
global constant and that R_ToplevelContext is the bottom of the
context stack... sys.on.exit is a function that calls a .Internal.
This inserts an extra context layer - calling the .Internal directly
works - and one just had to look one level further up.

Will commit for 0.65.1 in a moment.

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk)             FAX: (+45) 35327907
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