First of all some code that behaves as expected:
#include <iostream>
#include <sstream>
using namespace std;
int main(int argc, char argv[])
{
stringstream name;
name << "abcde";
name << 123;
cout << name.str() << endl;
}
Output: abcde123
Now if we change the first two lines of main() to get:
int main(int argc, char argv[])
{
stringstream name("abcde");
name << 123;
cout << name.str() << endl;
}
the output changes to: 123de. So the initialization string gets overwritten
instead of appending the data. Inserting name.seekp(0, ios::end); helps, but
only for compiler version 4.0, not for 4.1 (at least I think so, I couldn't
test this enough ATM).
Now trying to get the right behaviour by using stringstream name("abcde",
ios::app); or stringstream name("abcde", ios::ate); leads to another
interesting output: abcde. The input gets completely ignored.
In my Stroustrup I only found a specification for the behaviour of
ostringstream, not for stringstream but using ostringstream instead of
stringstream doesn't change anything and I don't think stringstream should
behave like this anyway (especially in contrast to the first example).
I hope I didn't waste your time because the bug already got fixed in 4.3 or
something, but I couldn't find anything neither in Bugzilla nor via Google.
Many thanks and kind regards,
Christian
PS: I tested this with g++ 4.0.3 on Ubuntu GNU/Linux, with g++ 4.1 on some SuSE
and with g++ 3.4.3 on SunOS 5.10, all Intel CPUs.
--
Summary: stringstream behaves unexpectedly
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: cmertes at techfak dot uni-bielefeld dot de
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31456
