Hi,
On 06/26/2014 01:36 PM, Radford Neal wrote:
PROTECT(dfm=lang3(install("data.frame"),df,ScalarLogical(FALSE)));
SET_TAG(CDDR(dfm), install("stringsAsFactors")) ;
SEXP res = PROTECT(eval(dfm,R_GlobalEnv));
PROTECT(head=lang3(install("head"),res,ScalarInteger(1)));
head = PROTECT(eval(head,R_GlobalEnv));
I tried the above following , it seemed to be not working . Can you please
help.
Can you elaborate? The above code works AFAICT ...
The code is actually not safe. Both "install" and "SalarLogical/Integer"
potentially allocate memory, so at least one needs to be protected before
callling lang3. (Passing one such argument would be OK, since lang3
protects its arguments, but it doesn't get a chance to do that while they
are still being evaluated.)
How true but who can blame him? The Writing R Extensions manual
contains the same mistake:
SEXP mkans(double x)
{
SEXP ans;
ans = PROTECT(allocVector(REALSXP, 1));
REAL(ans)[0] = x;
UNPROTECT(1);
return ans;
}
double feval(double x, SEXP f, SEXP rho)
{
defineVar(install("x"), mkans(x), rho);
return REAL(eval(f, rho))[0];
}
Reported here more than 6 years ago and never fixed:
https://stat.ethz.ch/pipermail/r-devel/2008-January/048040.html
Cheers,
H.
Now, I'm not sure this is the source of the actual problem, since both
"data.frame" and "head" presumably already exist, so the install won't
actually allocate memory. But this is not a safe coding method in
general.
Radford Neal
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
--
Hervé Pagès
Program in Computational Biology
Division of Public Health Sciences
Fred Hutchinson Cancer Research Center
1100 Fairview Ave. N, M1-B514
P.O. Box 19024
Seattle, WA 98109-1024
E-mail: hpa...@fhcrc.org
Phone: (206) 667-5791
Fax: (206) 667-1319
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
