R devel - Feb 2007 - Problem using ofstream in C++ class in package for MacOS X

Dear all,

I am currently learning how to create R packages using C++ classes.
For this purpose I have written a small package MyClass (which I try
to attach since I do not have access to a website).

MyClass has methods WriteFileC() and WriteFileCpp() which implement
C-style and C++-style writing of a table to a file using FILE or
ofstream respectively, and the corresponding R-functions writeFileC.R
and writeFileCpp.R.

While I can compile and execute my package w/o problems on Fedora Core 4,
I can only execute writeFileC.R on my Intel-MacBook Pro, but not 
writeFileCpp.R.
Executing my functions I get the following output:

 > library(MyClass)

Welcome to MyClass
 > writeFileC("myout_fileC.txt")
[1] "outfile =  myout_fileC.txt"
Writing file myout_fileC.txt using C style.
---MyClassA::MyClassA()---------
---MyClassA::WriteFileC---------
<20> records exported.
---MyClassA::~MyClassA()---------
[1] "writeFileC finished"
NULL
 > writeFileCpp("myout_fileCpp.txt")
[1] "outfile =  myout_fileCpp.txt"
Writing file myout_fileCpp.txt using C++ style.
---MyClassA::MyClassA()---------
---MyClassA::WriteFileCpp---------

 *** caught bus error ***
address 0x6, cause 'non-existent physical address'

Traceback:
 1: .C("WriteFileCpp", as.character(outfile), PACKAGE =
"MyClass")
 2: writeFileCpp("myout_fileCpp.txt")


While I understand, that C++ iostreams are best avoided, since there is
no guarantee that the output will appear in the R console (as mentioned
on page 62 of R-exts.pdf), I do not understand why I cannot use ofstream,
which is isolated in a C++ method only.

Is there a way how to use ofstream on MacOS X or is this a limit of the
current Mac implementation?

Thank you in advance.
Best regards
Christian
_._._._._._._._._._._._._._._._
C.h.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
_._._._._._._._._._._._._._._._

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On 4 February 2007 at 20:17, cstrato wrote:
| I am currently learning how to create R packages using C++ classes.

Congratulations :)    

[ This reminds me to email Oleg (CC'ed). Oleg, your HOWTO is a very useful.
Would you consider adding a section on Dominick's most excellent
RcppTemplate
package which makes writing code to go back and forth between R and C++ soooo
much easier?  ]

| For this purpose I have written a small package MyClass (which I try
| to attach since I do not have access to a website).
[...]
| While I can compile and execute my package w/o problems on Fedora Core 4,

Works for me too on Debian.

[...]
|  > writeFileCpp("myout_fileCpp.txt")
| [1] "outfile =  myout_fileCpp.txt"
| Writing file myout_fileCpp.txt using C++ style.
| ---MyClassA::MyClassA()---------
| ---MyClassA::WriteFileCpp---------
| 
|  *** caught bus error ***
| address 0x6, cause 'non-existent physical address'
| 
| Traceback:
|  1: .C("WriteFileCpp", as.character(outfile), PACKAGE =
"MyClass")
|  2: writeFileCpp("myout_fileCpp.txt")
| 
| 
| While I understand, that C++ iostreams are best avoided, since there is
| no guarantee that the output will appear in the R console (as mentioned
| on page 62 of R-exts.pdf), I do not understand why I cannot use ofstream,
| which is isolated in a C++ method only.
| 
| Is there a way how to use ofstream on MacOS X or is this a limit of the
| current Mac implementation?

Can you get to this in a debugger on MacOS X?  Just glancing at your code I
saw nothing obviously sticking out...

Dirk
 
-- 
Hell, there are no rules here - we're trying to accomplish something. 
                                                  -- Thomas A. Edison

Dear Jochen

Thank you, there seems to be a problem with accessing memory but 
probably not in my simple program.
Here are the essential parts:

1. R-function:
"writeFileCpp" <-
function(outfile=character(0)) {
   r <- .C("WriteFileCpp",as.character(outfile),
PACKAGE="MyClass");
   return();
}

2. R-wrapper:
   void WriteFileCpp(char **outfile)
   {
      MyClassA *classA = new MyClassA();
      classA->WriteFileCpp(outfile[0]);
      delete classA;
   }

3. C++ method:
void MyClassA::WriteFileCpp(const char *outfile)
{
   ofstream output(outfile, ios::out);
   output << 21 << endl;
   output.close();
}

This crashes with "non-existent physical address"

Interestingly, the following C++ method works:
void MyClassA::WriteFileCpp(const char *outfile)
{
   ofstream output(outfile, ios::out);
//   output << 21 << endl;
   output.close();
}

This means, that the operator "<<" seems to cause the problem,
but why?

Best regards
Christian



Jochen Laubrock wrote:
> Hi cstrato,
>
>
> On 04.02.2007, at 22:47, cstrato wrote:
>
>> ostream.tcc
>>
>
>
> On my system (Mac OS X), ostream.tcc seems to be just a part of the 
> FSF/GNU implementation of the stl, as
>
> head -n 40 /usr/include/c++/4.0.0/bits/ostream.tcc
>
> gives
>
>> // This file is part of the GNU ISO C++ Library.  This library is free
>> // software; you can redistribute it and/or modify it under the
>> [...]
>> /** @file ostream.tcc
>> *  This is an internal header file, included by other library headers.
>> *  You should not attempt to use it directly.
>> */
>>
>> //
>> // ISO C++ 14882: 27.6.2  Output streams
>
>
> I think your error looks more like you are accessing invalid memory, 
> maybe a dangling pointer ?
>
> hth, jochen
>