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

[iuke-tier@ey m@iii@g oii uiow@@edu]

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.

Best bet to narrow this down is for someone with a good Windows setup
who can reproduce this to bisect the svn commits and see at what
commit this started happening. Unfortunately my office Windows machine
isn't responding and it will probably take some time to get that
fixed.

Best,

luke

>
> -pd
>
>
>> On 7 Jun 2020, at 16:00 , Jeroen Ooms <jeroenooms using gmail.com> wrote:
>>
>> On Sun, Jun 7, 2020 at 3:13 AM Fox, John <jfox using mcmaster.ca> wrote:
>>>
>>> Hi,
>>>
>>> The following code, from the examples in ?TkWidgets , immediately crashes R 4.0.1 for Windows:
>>>
>>> --------------------- snip --------------------
>>> library("tcltk")
>>> tt <- tktoplevel()
>>> label.widget <- tklabel(tt, text = "Hello, World!")
>>> button.widget <- tkbutton(tt, text = "Push",
>>>         command = function()cat("OW!\n"))
>>> tkpack(label.widget, button.widget) # geometry manager
>>> --------------------- snip --------------------
>>
>>
>> I can reproduce this. The backtrace shows the crash happens in
>> dotTclObjv  [/src/library/tcltk/src/tcltk.c using 243 ]. This looks like a
>> bug that was introduced by commit 78408/78409 about a month ago. I
>> think the problem is that this commit changes 'calloc' to 'Calloc'
>> without changing the corresponding 'free' to 'Free'.
>>
>> This has nothing to do with the Windows build or installation. Nothing
>> has changed in the windows build procedure between 4.0.0 and 4.0.1.
>>
>> ______________________________________________
>> R-devel using r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>
>

-- 
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