[Bug c++/14417] New: output streams and post-increment operator have incorrect output.

[Bug c++/14417] New: output streams and post-increment operator have incorrect output.

[mcvick_e at iname dot com]

Utilizing the post increment operator within a stream operation does not result
in the expected output.  Output is reversed.  Based on the grammer of the
language, this should work as expected and not as currently implemented.

THe following program will replicate the problem:

#include <iostream>
#include <fstream>

using namespace std;


char *str = "0123456789ABCDEF";

int main(int argc, char **argv)
{
   char *ptr;

#if defined(COUT_TOO)
   ptr = str;

   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << *ptr++ << *ptr++ << ' ';
   cout << endl;
#endif

   ostream  *outStream;

   outStream = new ofstream("foo.txt");
   ptr = str;

   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << *ptr++ << *ptr++ << ' ';
   *outStream << endl;

   delete outStream;

   // Same concept, different syntax works.

#if defined(COUT_TOO)
   ptr = str;

   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << *ptr++;
   cout << *ptr++ << ' ';
   cout << endl;
#endif

   outStream = new ofstream("bar.txt");
   ptr = str;

   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << *ptr++;
   *outStream << *ptr++ << ' ';
   *outStream << endl;

}


The above program was compiled with the following command:

g++ -O0 -o foobar test.cxx -DCOUT_TOO


The output on the screen and found in the files is thus:

10 32 54 76 98 BA DC FE 
01 23 45 67 89 AB CD EF 

The specs of the compiler obtained with g++ -v is:

Reading specs from /usr/lib/gcc-lib/i386-redhat-linux/3.3.3/specs
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --disable-libunwind-exceptions --with-system-zlib
--enable-__cxa_atexit --host=i386-redhat-linux
Thread model: posix
gcc version 3.3.3 20040216 (Red Hat Linux 3.3.3-2)

I have even tried the latest snapshot of GCC 3.3.3 and it fails as well.  I also
compiled 3.3.1 and used it with the same results.

-- 
           Summary: output streams and post-increment operator have
                    incorrect output.
           Product: gcc
           Version: 3.3.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: mcvick_e at iname dot com
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-redhat-linux
  GCC host triplet: i386-redhat-linux
GCC target triplet: i386-redhat-linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417

[Bug c++/14417] output streams and post-increment operator have incorrect output.

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-03-03 21:15 -------
No bug, please read the page on frequently reported bugs. operator<< 
is not a sequence point, so the question of when the pointer is  
increased and when it is dereferenced is undefined. 
 
W. 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |INVALID


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417

[Bug c++/14417] output streams and post-increment operator have incorrect output.

[mcvick_e at iname dot com]

------- Additional Comments From mcvick_e at iname dot com  2004-03-03 23:09 -------
(In reply to comment #1)
> No bug, please read the page on frequently reported bugs. operator<< 
> is not a sequence point, so the question of when the pointer is  
> increased and when it is dereferenced is undefined. 
>  
> W. 

It's interesting that this has worked historically.  I see g++ 2.9.5 work 
appropriately on our Sun Solaris stations, as well as V3 work appropriately on 
our Macintosh systems.

I guess we'll resort to using something that actually works as most people 
would expect it to.

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417

[Bug c++/14417] output streams and post-increment operator have incorrect output.

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-03-03 23:23 -------
The standard says that the behavior of your program is undefined in this 
case. Newer compilers are better at optimizing code, so they trip users 
writing undefined code more often. It's not the compiler's fault if it 
reorders code that the standard allows it to reorder. 
 
W. 
 
PS: To understand what's going on, read the entry on -Wsequence-point 
in the manual. 

-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417

[Bug c++/14417] output streams and post-increment operator have incorrect output.

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-08-05 14:57 -------
Reopen these bugs... 

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |UNCONFIRMED
         Resolution|INVALID                     |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417

[Bug c++/14417] output streams and post-increment operator have incorrect output.

[bangerth at dealii dot org]

------- Additional Comments From bangerth at dealii dot org  2004-08-05 15:01 -------
...mark as duplicate of PR 11751. 

*** This bug has been marked as a duplicate of 11751 ***

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=14417