[Rd] [External] use of the tcltk package crashes R 4.0.1 for Windows

[Avraham Adler]

Jeroen, how "reactive" are the rtools40 scripts. Will they pull the latest
version committed by Dr. Tierney or is there something which must be done
manually prior to we end-users rebuilding from source?

Thank you,

Avi

On Sun, Jun 7, 2020 at 11:01 PM peter dalgaard <pdalgd using gmail.com> wrote:

> Ah, I see it now:
>
> The remapping of free() to Rm_free() and calloc() to Rm_calloc() happens
> in memory.c, but not in tcltk.c; the macro Calloc in R_ext/RS.h maps to a
> call to R_chk_alloc which is defined in memory.h; RS.h is included in
> tcltk.c, so tcltk.c winds up calling Rm_calloc() via Calloc(), but then the
> NON-remapped free(), and the walls come tumbling down.
>
> If the  "#if defined(Win32)" block had been inside RS.h, the problem
> wouldn't arise.
>
> -pd
>
> > On 8 Jun 2020, at 00:03 , luke-tierney using uiowa.edu wrote:
> >
> > I've committed the change to use Free instead of free in tcltk.c and
> > sys-std.c (r78652 for R-devel, r78653 for R-patched).
> >
> > We might consider either moving Calloc/Free out of the Windows
> > remapping or moving the remapping into header files so everything
> > seeing our header files uses our calloc/free. Either would be less
> > brittle that the current status.
> >
> > Best,
> >
> > luke
> >
> > On Sun, 7 Jun 2020, peter dalgaard wrote:
> >
> >>
> >>
> >>> On 7 Jun 2020, at 18:59 , Jeroen Ooms <jeroenooms using gmail.com> wrote:
> >>>
> >>> On Sun, Jun 7, 2020 at 5:53 PM <luke-tierney using uiowa.edu> wrote:
> >>>>
> >>>> On Sun, 7 Jun 2020, peter dalgaard wrote:
> >>>>
> >>>>> So this wasn't tested for a month?
> >>>>>
> >>>>> Anyways, Free() is just free() with a check that we're not freeing a
> null pointer, followed by setting the pointer to NULL. At that point of
> tcltk.c, we have
> >>>>>
> >>>>> for (objc = i = 0; i < length(avec); i++){
> >>>>>      const char *s;
> >>>>>      char *tmp;
> >>>>>      if (!isNull(nm) && strlen(s = translateChar(STRING_ELT(nm,
> i)))){
> >>>>>          //  tmp = calloc(strlen(s)+2, sizeof(char));
> >>>>>          tmp = Calloc(strlen(s)+2, char);
> >>>>>          *tmp = '-';
> >>>>>          strcpy(tmp+1, s);
> >>>>>          objv[objc++] = Tcl_NewStringObj(tmp, -1);
> >>>>>          free(tmp);
> >>>>>      }
> >>>>>      if (!isNull(t = VECTOR_ELT(avec, i)))
> >>>>>          objv[objc++] = (Tcl_Obj *) R_ExternalPtrAddr(t);
> >>>>>  }
> >>>>>
> >>>>> and I can't see how tmp can be NULL at the free(), nor can I see it
> mattering if it is not set to NULL (notice that it goes out of scope with
> the for loop).
> >>>>
> >>>> Right. And the calloc->Calloc change doesn't look like an issue either
> >>>> -- just checking for a NULL.
> >>>>
> >>>> If the crash is happening in free() then that most likely means
> >>>> corrupted malloc data structures. Unfortunately that could be
> >>>> happening anywhere.
> >>>
> >>> Writing R extensions, section 6.1.2 says: "Do not assume that memory
> >>> allocated by Calloc/Realloc comes from the same pool as used by
> >>> malloc: in particular do not use free or strdup with it."
> >>>
> >>> I think the reason is that R uses dlmalloc for Calloc on Windows:
> >>>
> https://github.com/wch/r-source/blob/c634fec5214e73747b44d7c0e6f047fefe44667d/src/main/memory.c#L94-L103
> >>
> >> But that section #defines calloc and free to Rm_... counterparts in
> lockstep? (I assume that is where dlmalloc comes in?)
> >>
> >> Anyways, does it actually work to change free() to Free()? If so, then
> all this post mortem analysis is rather a moot point.
> >>
> >> -pd
> >>
> >>
> >
> > --
> > Luke Tierney
> > 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-tierney using uiowa.edu
> > Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu
>
> --
> Peter Dalgaard, Professor,
> Center for Statistics, Copenhagen Business School
> Solbjerg Plads 3, 2000 Frederiksberg, Denmark
> Phone: (+45)38153501
> Office: A 4.23
> Email: pd.mes using cbs.dk  Priv: PDalgd using gmail.com
>
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>

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