Le 23 juin 2014 à 15:20, cstrato <cstr...@aon.at> a écrit :
> Dear all,
>
> Since many years the following C++ code does compile on ALL Bioconductor
> servers (Linux, Windows, Mac) without any warnings:
>
> Int_t numsels = 0; //number of selected entries
> ...
> for (Int_t i=0; i<size; i++) {
> numsels = (arrMask[i] == 1) ? ++numsels : numsels;
> }//for_i
This is confusing. I would write the loop body like this:
numsels += (arrMask[i] == 1) ;
or preferably using the STL:
Int_t numsels = std::count( begin(arrMask), end(arrMask), 1 ) ;
or some other variation of this, i.e. perhaps you don’t have a C++11 compiler,
so perhaps one of these depending on what is arrMask:
Int_t numsels = std::count( arrMask.begin(), arrMask.end(), 1 ) ;
Int_t numsels = std::count( arrMask, arrMask + size, 1 ) ;
Romain
> Even on the recently added release server 'zin2' Linux (Ubuntu 12.04.4 LTS)
> the above code compiles w/o warnings.
>
> However, on the new development server 'zin1' Linux (Ubuntu 12.04.4 LTS) I
> get suddenly the following warning message:
>
> Found the following significant warnings:
> XPSPreProcessing.cxx:3026:56: warning: operation on ‘numsels’ may be
> undefined [-Wsequence-point]
>
> Interestingly, both servers do not only run the same version of Ubuntu, but
> also the same version of the C++ compiler, i.e. g++ (Ubuntu/Linaro
> 4.6.3-1ubuntu5) 4.6.3, and use the same flags, see:
> http://bioconductor.org/checkResults/2.14/bioc-LATEST/zin2-NodeInfo.html
> http://bioconductor.org/checkResults/devel/bioc-LATEST/zin1-NodeInfo.html
>
> My question is now, why do I suddenly get the compiler warning?
>
> The reason why I ask at R-devel and not Bioc-devel is that it may not only be
> a Bioc question, since I found the following links:
> http://c-faq.com/expr/seqpoints.html
> http://stackoverflow.com/questions/16838884/why-i-got-operation-may-be-undefined-in-statement-expression-in-c
>
> I am not sure if I understand the meaning, but until now I have never got any
> warning from any compiler the I have used (including MS Visual C++).
>
> Do I really have to replace '++numsels' with 'numsels+1'?
>
> Best regards,
> Christian
> _._._._._._._._._._._._._._._._._._
> C.h.r.i.s.t.i.a.n S.t.r.a.t.o.w.a
> V.i.e.n.n.a A.u.s.t.r.i.a
> e.m.a.i.l: cstrato at aon.at
> _._._._._._._._._._._._._._._._._._
>
> ______________________________________________
> R-devel@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-devel
______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
