How allocate STRSXP outside of gc

-----Original Message-----
From: Duncan Temple Lang [mailto:duncan@wald.ucdavis.edu] 
Sent: Tuesday, April 12, 2005 12:52 PM
To: Vadim Ogranovich
Cc: r-devel@stat.math.ethz.ch
Subject: Re: [Rd] How allocate STRSXP outside of gc

Look at R_PreserveObject to see if it will do what you want.
It certainly used to.

SEXP getFoo()
{
  static SEXP val = NULL;

  if(!val) {
    val = mkChar("foo");
    R_PreserveObject(val);
  }

  return(val);
}


You may want to have a routine that is called when the 
package is unloaded that calls R_ReleaseObject().

Alternatively, store the object in a package's namespace 
environment and it won't be gc'ed.

 D.


Vadim Ogranovich wrote:

Hi,
 
I am trying to figure a way to allocate a string SEXP so that gc() 
won't ever collect it.
 
Here is a little bit of a background. Suppose I want to write a 
.Call-callable function that upon each call returns the same value, 
say
mkChar("foo"):
 
SEXP getFoo() {
   return mkChar("foo");
}
 
The above implementation doesn't take advantage of the fact that
mkChar("foo") could be pre-computed only once, and then the 

function 

would return the pre-computed value. So the question is how 

to create 

this precomputed value.
 
 
The closest thing I could find in the sources is 

R_NaString, but I was 

not able to trace down how it comes about.
 
 
Thanks,
Vadim
 
 
P.S. I was able to solve a similar problem with symbols. If 

I need a 

symbol "foo", I do
 
static SEXP  FooSymbol = install("foo");
 
and then use FooSymbol instead of install("foo")
 
 
 

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-- 
Duncan Temple Lang                duncan@wald.ucdavis.edu
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