[Bug libstdc++/28278] formatted I/O and calliing width(0)

[Bug libstdc++/28278] formatted I/O and calliing width(0)

[mikeus at hotmail dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28278

Michael <mikeus at hotmail dot ru> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |mikeus at hotmail dot ru

--- Comment #1 from Michael <mikeus at hotmail dot ru> 2010-12-27 11:25:51 UTC ---
Can anybody fix this bug?

------- code: -------
#include<iostream>
using namespace std;

int main()
{
  cout.setf(ios_base::fixed);
  cout.precision(3);
  cout.width(20);
  cout.fill('#');

  cout << (double)1.123456789 << endl;
  cout << (double)0.123456789 << endl;
  cout << (double)10.123456789 << endl;
}
---------------------

------- output: -------
###############1.123
0.123
10.123
-----------------------

------- expected: -------
###############1.123
###############0.123
##############10.123
-------------------------

It's just sad... :^(((

[Bug libstdc++/28278] formatted I/O and calliing width(0)

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28278

--- Comment #2 from Paolo Carlini <paolo.carlini at oracle dot com> 2010-12-27 12:12:13 UTC ---
The snippet you posted has nothing to do with the issue discussed here, which
is about *when exactly* calling width(0) toward the end of the insertion
operation (there are minor inconsistencies in the Standard detectable when the
insertion proper throws). But in any case, per the letter of both C++03 and
C++0x , during the arithmetic insertion at some point width(0) has to be
called, normally by the num_put facet in Stage 3. Thus the behavior we are
implementing vs your snippet is already Ok, no bug to fix (if you want a
practical check, Sun Studio behaves the same).

[Bug libstdc++/28278] formatted I/O and calling width(0)

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28278

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2010-12-27 14:31:39 UTC ---
(In reply to comment #1)
> Can anybody fix this bug?

Don't be sad, your bug is easy to fix:

> ------- code: -------
> #include<iostream>
> using namespace std;
> 
> int main()
> {
>   cout.setf(ios_base::fixed);
>   cout.precision(3);
>   cout.width(20);
>   cout.fill('#');
> 
   cout << std::setw(20) << 1.123456789 << endl;
   cout << std::setw(20) << 0.123456789 << endl;
   cout << std::setw(20) << 10.123456789 << endl;
> }

Fixed.

[Bug libstdc++/28278] formatted I/O and calling width(0)

[mikeus at hotmail dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28278

--- Comment #4 from Michael <mikeus at hotmail dot ru> 2010-12-27 15:12:50 UTC ---
:))OK.
( I merely have looked at 'ios_base state functions' chapter in C++0x draft and
not found any mention that any preset state of a stream may be lost after an
output operation.  It turns out that the width is the (only) state which can
be(inconsequently) lost after an output operation. )

[Bug libstdc++/28278] formatted I/O and calling width(0)

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=28278

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Created attachment 56765
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=56765&action=edit
Martin's test code

Attaching the test code here, in case the link stops working.