[Rd] as.environment.list provides inconsistent results under torture

[luke-tierney at uiowa.edu]

No. Lots of internal functions expect their callers to protect their
arguments, for efficiency reasons. eval is called very often and
almost always with argument that are protected because they are in the
evaluation engine, so it would be wasteful and potentially very costly
if eval protected its arguments every time it is called. (I don't
tknow what the cost would be to do so in the current implementation
but it could be prohibitive if we moved to some different approaches,
so for now we whould continue to expect callers of eval to make sure
the argumetns are protected.)

Best,

luke

On Tue, 11 Jan 2011, Simon Urbanek wrote:

> Interesting, I'd argue that the bug is in eval() not protecting its arguments since the usual convention is for functions to protect its arguments...
>
> On Jan 11, 2011, at 2:33 PM, Romain Francois wrote:
>
>> Hello,
>>
>> Using R-devel (rev 53950), I get inconsistent results with as.environment( VECSXP ) when gctorture is on.
>>
>> Consider:
>>
>> a <- list( aa = rnorm, bb = runif )
>> gctorture(TRUE)
>> as.environment( a )
>>
>> The last line sometimes produces the correct environment, but sometimes I get errors. Here are the three situations:
>>
>> # good
>>> as.environment( a )
>> <environment: 0x100b1c978>
>>
>> # not good
>>> as.environment( a )
>> Erreur dans length(x) : 'x' est manquant
>>
>> # not good either
>>> as.environment( a )
>> Erreur dans list(NULL, list(aa = function (n, mean = 0, sd = 1)  :
>>  correspondance partielle de chaînes de caractères incorrecte
>>
>>
>> Is it because the call made by lang4 is not protected while evaluated in this line :
>>
>>    case VECSXP: {
>> 	/* implement as.environment.list() {isObject(.) is false for a list} */
>> 	return(eval(lang4(install("list2env"), arg,
>> 			  /*envir = */R_NilValue, /* parent = */R_EmptyEnv),
>> 		    rho));
>>    }
>>
>>
>> (BTW, this was detected in a looooooooong Rcpp-devel thread. See http://comments.gmane.org/gmane.comp.lang.r.rcpp/1336)
>>
>> Romain
>>
>> --
>> Romain Francois
>> Professional R Enthusiast
>> +33(0) 6 28 91 30 30
>> http://romainfrancois.blog.free.fr
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>> |- http://bit.ly/gpCSpH : Evolution of Rcpp code size
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>>
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>>
>>
>
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-- 
Luke Tierney
Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke at stat.uiowa.edu
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