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From "Martin Sebor (JIRA)" <j...@apache.org>
Subject [jira] Created: (STDCXX-308) filebuf dtor doesn't close fd after exception
Date Mon, 11 Dec 2006 16:31:21 GMT
filebuf dtor doesn't close fd after exception
---------------------------------------------

                 Key: STDCXX-308
                 URL: http://issues.apache.org/jira/browse/STDCXX-308
             Project: C++ Standard Library
          Issue Type: Bug
          Components: 27. Input/Output
    Affects Versions: 4.1.2, 4.1.3
         Environment: all
            Reporter: Martin Sebor
         Assigned To: Martin Sebor


-------- Original Message --------
Subject: Re:  aCC 3.70 -AA fd's close not being called.
Date: Thu, 7 Dec 2006 23:17:55 -0800 (PST)
From: Dennis Handly <dhandly@cup.hp.com>
To: sebor@roguewave.com
CC: Boris.Gubenko@hp.com, al.simons@hp.com, dhandly@cup.hp.com

It appears this problem is still in the apache code:
http://svn.apache.org/repos/asf/incubator/stdcxx/trunk/include/fstream.cc

It seems to violate 27.8.1.3(6), which says it always "finally" calls
"as if" fclose(3).  And returns an error if any calls fail.

================================================================
>From: "Levie, Barry" <barry.levie@hp.com>
Date: Thu, 7 Dec 2006 15:36:33 -0000
Subject: aCC 3.70 -AA fd's close not being called.

I am not sure if this exactly represents the problem the customer is
having as I am still waiting for more details (versions/test case etc
etc). However this could be close and I think it shows a problem.

Why does the ofstream destructor not close the file descriptor when its
called after its thrown an exception for "out of disk space".  

This aCC 3.70 -AA example shows an ever increasing number of open file
descriptors in glance

# what /usr/lib/libstd_v2.2:
   HP aC++ B3910B A.03.30 C++ Standard Library (RogueWave Version 2.02.01)

#include <iostream>
#include <fstream>
#include <string.h>
using namespace std;
struct dummy {
   dummy() { cout << "\ndummy created \n" ;}
   ~dummy() { cout << "\ndummy deleted \n"; }
};
void bar() {
  char buf[1024*1024];
  memset(buf,'A',1024*1024);
  buf[1024*1024 -1] = 0;
  ofstream of;
  dummy df;
  of.exceptions(ofstream::eofbit | ofstream::failbit | ofstream::badbit);
  try {
    of.open("/home/test.txt"); // this is on a volume that is nearly full.
    while(1) {
        of << buf;
    }
  }
  catch(ofstream::failure& e) {
    cout << "\nException write/file";
  }
}
int main () {
   while(1) bar();
}

# ./a.out

dummy created
msgcnt 160 vxfs: mesg 001: vx_nospace - /dev/vg00/lvol5 file system full
(1 block extent)
Exception write/file
dummy deleted
....

Glance output shows

D  File Name              Type   Mode  Count Offset
---------------------------------------------------
  0 /dev/pts/ta            stream rd/wr   6 333822
  1 /dev/pts/ta            stream rd/wr   6 333822
  2 /dev/pts/ta            stream rd/wr   6 333822
  3 /home/test.txt         reg    write   1 101957632
  4 /home/test.txt         reg    write   1 101957632
  5 /home/test.txt         reg    write   1 101957632
...
================================================================
>From: Dennis Handly <dhandly@cup.hp.com>
Date: Thu, 7 Dec 2006 23:03:08 -0800 (PST)
To: acxx@cup.hp.com, barry.levie@hp.com
Subject: Re:  aCC 3.70 -AA fd's close not being called.

>From: "Levie, Barry" <barry.levie@hp.com>
>I am not sure if this exactly represents the problem the customer is
>having as I am still waiting for more details (versions/test case etc
>etc). However this could be close and I think it shows a problem.

>Why does the ofstream destructor not close the file descriptor when its
>called after its thrown an exception for "out of disk space".  

A highly modified version works for me.
And it isn't closed on the throw but by falling off the bar body.

>This aCC 3.70 -AA example shows an ever increasing number of open file
>descriptors in glance

Hmm.

># what /usr/lib/libstd_v2.2:
>   HP aC++ B3910B A.03.30 C++ Standard Library (RogueWave Version 2.02.01)

This obsolete version isn't supported.

Here is what I have and it shows close being called after I throw.

I've manually modified the write return to -1 and that throws and is caught.
(The debugger was broken and it didn't really happen.  )-:

#include <iostream>
#include <fstream>
#include <string.h>
#include <stdio.h>
using namespace std;
struct dummy {
   dummy() { fprintf(stdout, "dummy created\n"); fflush(stdout); }
   ~dummy() { fprintf(stdout, "dummy deleted\n"); fflush(stdout);  }
};
extern "C" int _close(int fd);
extern "C" int close(int fd) {
   if (fd > STDERR_FILENO) {
      fprintf(stdout, "close(%d)\n", fd);
      fflush(stdout);
   }
   return _close(fd);
}
char buf[1024];
void bar() {
   ofstream of;
   dummy df;
   of.exceptions(ofstream::eofbit | ofstream::failbit | ofstream::badbit);
   try {
      of.open("test.txt"); // this is on a volume that is nearly full.
      fprintf(stdout, "FD = %d\n", of.rdbuf()->fd());
      fflush(stdout);
      for (int i = 0; i < 2; ++i)
         of << buf;
      throw ios_base::failure();
   }
   catch(ofstream::failure &e) {
      fprintf(stdout, "Exception write/file\n");
      fflush(stdout);
   }
}
int main() {
   memset(buf,'A',sizeof(buf));
   buf[sizeof(buf)-1] = '\0';
   int i;
   for (i = 0; i < 10; ++i)
      bar();
}

Ah, it's catch 22.  When it destroys ofstream it calls close, which calls
overflow which calls _C_write which calls write which gets an error and
then returns before closing.

It seems it is working as designed be RW.

But this seems to violate 27.8.1.3(6), which says it always calls
fclose(3).

File a CR.


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