R devel - May 2000 - Documentatio: typo in Writing R Extensions (PR#557)

Full_Name: stephen eglen
Version: 1.0.0
OS: Unix (OSF/1)
Submission from: (NULL) (129.215.238.26)


Hi,
in the documentation `Writing R Extensions', the section 3.6.1  (handling
the
effects of garbage collection) has the following typo:

 Protecting a SEXP pointer protexts ...

Should  that be `protects'?

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On Tue, 30 May 2000 stephen@anc.ed.ac.uk wrote:
> Full_Name: stephen eglen
> Version: 1.0.0
> OS: Unix (OSF/1)
> Submission from: (NULL) (129.215.238.26)
> 
> 
> Hi,
> in the documentation `Writing R Extensions', the section 3.6.1 
(handling the
> effects of garbage collection) has the following typo:
> 
>  Protecting a SEXP pointer protexts ...
> 
> Should  that be `protects'?
It is already `protects' in the current sources (R-devel): I didn't
check
1.0.1.  Not sure why you submitted this twice (PR#557 and PR#558)?

-- 
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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stephen@anc.ed.ac.uk writes:
> Full_Name: stephen eglen
> Version: 1.0.0
> OS: Unix (OSF/1)
> Submission from: (NULL) (129.215.238.26)
> 
> 
> Hi,
> in the documentation `Writing R Extensions', the section 3.6.1 
(handling the
> effects of garbage collection) has the following typo:
> 
>  Protecting a SEXP pointer protexts ...
> 
> Should  that be `protects'?
Yup. Already fixed in the development version.

Actually "SEXP pointer" is a bit like "ATM machine". SEXPs
are
pointers to SEXPREC, so is a SEXP pointer a (SEXPREC **) ? Besides,
one is not protecting the pointer but the object it points to (by
putting a pointer to it on the protection stack). This is
a common misconception:

 PROTECT(p);
 ...
 p = AllocSexp(....);

will not protect the new value of p. You need

 PROTECT(p);
 ...
 UNPROTECT(1);
 PROTECT(p = AllocSexp(....));

Hmm. Looks like the whole section needs going over. The stuff about
"ensuring that the pointer is updated" is bogus too (it is VECRECs
that move, not SEXPRECs). And the description of UNPROTECT_PTR is
vacuous at best.

-- 
   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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