[Rd] R Console Bug?

[Simon Urbanek]

Ah, so you're not using R console, you're using the R.app Mac-GUI. That one is not a terminal, so it has entirely different rules, because it is combining all four streams (stdout, stderr and WriteConsole for both output and message). Also for historical reasons macOS (the original) used to use \r as newline (unix has \n and Windows has \r\n) - for that reason your combination of \n\r doesn't work since it is ambiguous in the Mac context and treated as CR. If you want a proper newline, you can change your example to something like

   REprintf("\n   Processing data chunk %d of 3\n ",k+1);

Which makes sure the \n is interpreted as \r\n first and only then you follow with \r. I suppose we could sunset the special handling of \r since it is likely quite rare to see Mac line endings these days... you could file an issue against Mac-GUI. 

Cheers,
Simon



> On Apr 17, 2021, at 19:26, Morgan Morgan <morgan.emailbox using gmail.com> wrote:
> 
> Hi Simon,
> Thank you for the feedback.
> It is really strange that you have a different output.
> I have attached a picture of my R console.
> I am just trying to port some pure C code that prints progress bars to R but it does not seem to be printing properly.
> It seems I am doing something wrong with REprintf and R_FlushConsole.
> Best regards,
> Morgan
> 
> On Sat, Apr 17, 2021 at 12:36 AM Simon Urbanek <simon.urbanek using r-project.org> wrote:
> Sorry, unable to reproduce on macOS, in R console:
> 
> > dyn.load("test.so")
> > .Call("printtest",1e4L)
> 
>    Processing data chunk 1 of 3
>  [==============================] 100%
> 
>    Processing data chunk 2 of 3
>  [==============================] 100%
> 
>    Processing data chunk 3 of 3
>  [==============================] 100%
> NULL
> 
> But honestly I'm not sure sure I understand the report. R_FlushConsole is a no-op for terminal console and your code just prints on stderr anyway (which is not buffered). All this does is just a lot of \r output (which is highly inefficient anywhere but in Terminal by definition). Can you clarify what the code tries to trigger?
> 
> Cheers,
> Simon
> 
> 
> > On Apr 16, 2021, at 23:11, Morgan Morgan <morgan.emailbox using gmail.com> wrote:
> > 
> > Hi,
> > 
> > I am getting a really weird behaviour with the R console.
> > Here is the code to reproduce it.
> > 
> > 1/ C code: ---------------------------------------------------
> > 
> > SEXP printtest(SEXP x) {
> >  const int PBWIDTH = 30, loop = INTEGER(x)[0];
> >  int val, lpad;
> >  double perc;
> >  char PBSTR[PBWIDTH], PBOUT[PBWIDTH];
> >  memset(PBSTR,'=', sizeof(PBSTR));
> >  memset(PBOUT,'-', sizeof(PBOUT));
> >  for (int k = 0; k < 3; ++k) {
> >    REprintf("\n   Processing data chunk %d of 3\n",k+1);
> >    for (int i = 0; i < loop; ++i) {
> >      perc = (double) i/(loop-1);
> >      val  = (int) (perc * 100);
> >      lpad = (int) (perc * PBWIDTH);
> >      REprintf("\r [%.*s%.*s] %3d%%", lpad, PBSTR, PBWIDTH - lpad, PBOUT,
> > val);
> >      R_FlushConsole();
> >    }
> >    REprintf("\n");
> >  }
> >  return R_NilValue;
> > }
> > 
> > 2/ Build so/dll: ---------------------------------------------------
> > 
> > R CMD SHLIB
> > 
> > 3/ Run code :  ---------------------------------------------------
> > 
> > dyn.load("test.so")
> > .Call("printtest",1e4L)
> > dyn.unload("test.so")
> > 
> > 4/ Issue:  ---------------------------------------------------
> > If you run the above code in RStudio, it works well both on Mac and Windows.
> > If you run it in Windows cmd, it is slow.
> > If you run it in Windows RGui, it is slow but also all texts are flushed.
> > If you run it in Mac terminal, it runs perfectly.
> > If you run it in Mac R Console, it prints something like :
> >> .Call("printtest",1e4L)
> > [==============================] 100%NULL----------------------------]   0%
> > 
> > I am using R 4.0.4 (Mac) / 4.0.5 (Windows)
> > 
> > Is that a bug or am I doing something wrong?
> > 
> > Thank you
> > Best regards,
> > Morgan
> > 
> >       [[alternative HTML version deleted]]
> > 
> > ______________________________________________
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> > 
> 
> <Screenshot 2021-04-17.png>