That makes sense. No real reason not to use attributes anyway :) Le 21 août 2014 à 15:54, JJ Allaire <j...@rstudio.com> a écrit :
> Yes, the link posted by Matteo is what provoked us to make the change in Rcpp > Attributes to dance around the constructor/destructor issues. > > Net: If you are using attributes then this isn't a concern, if you are not > then you need the return value SEXP on the stack prior to RNGScope. > > On Thursday, August 21, 2014, Romain Francois <rom...@r-enthusiasts.com> > wrote: > Ah interesting. PutRNGstate does indeed allocate so might trigger GC. > https://github.com/wch/r-source/blob/fbf5cdf29d923395b537a9893f46af1aa75e38f3/src/main/RNG.c#L437 > > That's a whole new Pandora's box right there. > > Le 21 août 2014 à 12:10, Matteo Fasiolo <matteo.fasi...@gmail.com> a écrit : > >> Hi Romain and Gregor, >> >> maybe I am misunderstanding everything, but hasn't this problem been >> explained and solved here: >> >> http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-May/005838.html >> >> Best, >> >> Matteo >> >> >> >> >> On Thu, Aug 21, 2014 at 10:58 AM, Romain Francois <rom...@r-enthusiasts.com> >> wrote: >> >> Le 21 août 2014 à 11:47, Gregor Kastner <gregor.kast...@wu.ac.at> a écrit : >> >> > On Thu, 21 Aug 2014 11:34:23 +0200 >> > Romain Francois <rom...@r-enthusiasts.com> wrote: >> > >> > GK> Yep, sorry for the misuse of language. And I do understand going back >> > to >> > GK> GetRNGstate() and PutRNGstate() is a bit old school; but I can >> > definitely >> > GK> confirm that it seems to be safer than resorting do the >> > GK> constructor/destuctor magic. >> >> >> >> Compiler/Destructor is not magic. It is determinism. >> >> >> >> That's like feature #1 of C++. >> > >> > agreed: s/magic/automagic/g >> > >> >> And BTW it is definitely safer than any manual handling. >> > >> > I cannot say that in the current case, as relying on the destructor does >> > seem >> > to create problems (in rare cases, making it even worse!) if objects which >> > are to be returned are instantiated after the RNGScope object. Conditional >> > on >> > the fact the I understood JJ correctly, that is. >> >> Then it's a bug in how constructor or destructor is implemented in this >> class, probably with the counter. >> >> Or something invalidates the very assumptions of C++ here. Perhaps raw R api >> is called and the destructor is not called because of some long jump or >> something. >> >> Without a repex anyway, it is hard to diagnose what's happening. >> >> You're probably onto somthing, but going directly to the "destructor are not >> safe, I'll just use C function calls" is a dangerous route, soon you'll >> start using SEXP as you won't trust ctors/dtors of Rcpp objects do the right >> thing. >> >> > Manual handling works perfectly. >> > >> > Best, >> > /g >> >> _______________________________________________ >> Rcpp-devel mailing list >> Rcpp-devel@lists.r-forge.r-project.org >> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel >> >
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