[Bug libstdc++/22542] ostringstream ignores fenv settings (incorrect output)

[stefan dot becuwe at ua dot ac dot be]

--- Additional Comments From stefan dot becuwe at ua dot ac dot be  
2005-07-18 09:30 ---
(In reply to comment #2)
> Well, certainly, this is not a libstdc++-v3 bug: internally we are simply 
> printing floating point numbers using sprintf (or snprintf, when available), 
> as
> mandated by the standard. Actually, however, I'm not at all sure what's the
> point of your report: you are changing the rounding mode for floating point
> operations, but in the testcase there aren't: there is only the definition of
> p (taking place *before* any setround)

Ok, I'll reformulate it and I've even simplified the input.  4.5 is exactly
representable in double precision, regardless of the active rounding precision.
 It should always be 4.5.  What I would like to do is to have that double
precision input rounded to the number of digits given by .precision (1 in the
example) using stringstreams, taking into account the rounding mode.  In the
following example, I assign a value to p AFTER setting the rounding mode.  And
guess, for the 4 rounding modes I now get 4 instead 5 (in my original post). 
Although internally the value of p should be 4.5...  Again: two of the four
cases are wrong...  So, as far as I'm concerned, I still think there's an error
somewhere.


  s1.setf(ios::scientific, ios::floatfield);
  s1.setf(ios::showpoint, ios::floatfield);
  s1.precision(1);

  double p;

  fesetround(FE_TONEAREST);
  p = 4.5;
  s1 << p << ends;
  cout << "s1 = " << s1.str() << endl;

-- 
   What|Removed |Added

 Status|RESOLVED|UNCONFIRMED
 Resolution|INVALID |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22542

[Bug libstdc++/22542] ostringstream ignores fenv settings (incorrect output)

[stefan dot becuwe at ua dot ac dot be]

--- Additional Comments From stefan dot becuwe at ua dot ac dot be  
2005-07-18 08:48 ---
Created an attachment (id=9299)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=9299&action=view)
preprocessed file


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22542

[Bug libstdc++/22542] New: ostringstream ignores fenv settings (incorrect output)

[stefan dot becuwe at ua dot ac dot be]

There seems to be a problem when an ostringstream gets its input from, f.i., a
double.  I've noticed the problem for at least exact halfway cases such as 4.5.
 In two of the four cases, the output is incorrect.  The same behaviour is
present in g++ 4.0.0 (prerelease 20050319).

-- 
   Summary: ostringstream ignores fenv settings (incorrect output)
   Product: gcc
   Version: 3.3.4
Status: UNCONFIRMED
  Severity: normal
  Priority: P2
 Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: stefan dot becuwe at ua dot ac dot be
CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: gcc version 3.3.4 (pre 3.3.5 20040809)


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=22542

[Bug libstdc++/19091] New: problem with string to double conversion (overflow situation)

[stefan dot becuwe at ua dot ac dot be]

Following conversion should overflow, and not return 8.02393e-308.  Same
problem, although different output, when reading "4E308" from standard input.

#include 
#include 
using namespace std;
int main()
{
  double r;
  istringstream s("+4E308");
  s >> r;
  cout << r << endl;
}

-- 
   Summary: problem with string to double conversion (overflow
situation)
   Product: gcc
   Version: 3.3.2
Status: UNCONFIRMED
  Severity: normal
  Priority: P2
 Component: libstdc++
AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: stefan dot becuwe at ua dot ac dot be
CC: gcc-bugs at gcc dot gnu dot org
  GCC host triplet: i386 linux


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=19091