std::ios_base::setf() and std::ios_base::unsetf() do not set/clear the format
flags correctly
---------------------------------------------------------------------------------------------
Key: STDCXX-1059
URL: https://issues.apache.org/jira/browse/STDCXX-1059
Project: C++ Standard Library
Issue Type: Bug
Components: 27. Input/Output
Affects Versions: 4.2.1, 4.2.x, 4.3.x, 5.0.0
Environment: Solaris 10 and 11
Red Hat Linux, OpenSuSE Linux
Sun C++ Compilers 12.1, 12.2, 12.3
Defect is independent of platform and/or compiler
Reporter: Stefan Teleman
Fix For: 4.2.2, 4.2.x, 4.3.x, 5.0.0
std::ios_base::setf (fmtflags fl) and std::ios_base::unsetf (fmtflags fl)
do not set or clear the format flags correctly:
{code title=test.cc|borderStyle=solid}
#include <ios>
#include <iostream>
#include <fstream>
int main()
{
std::fstream strm;
std::ios_base::fmtflags fl;
int ret = 0;
fl = std::ios_base::dec;
strm.unsetf(fl);
fl = std::ios_base::hex;
strm.setf(fl);
strm.unsetf(fl);
if (strm.flags() & fl)
{
std::cerr << "failure to clear hex flags" << std::endl;
++ret;
}
return ret;
}
{code}
1. Output from GCC 4.5.0:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:19:37][1957]>> ./test-gcc
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:20:02][1958]>> echo $status
0
{noformat}
2. Output from Sun C++ 12.2 with stlport:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:20:24][1959]>> ./test-ss122-stlport
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:21:08][1960]>> echo $status
0
{noformat}
3. Output rom Sun C++ 12.2 with our patched stdcxx:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:21:09][1961]>> ./test-ss122-stdcxx
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:21:44][1962]>> echo $status
0
{noformat}
4. Output from Pathscale 4.0.12.1 (which did not patch stdcxx):
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:21:46][1963]>> ./test-pathscale
failure to clear hex flags
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:22:48][1964]>> echo $status
1
{noformat}
Simplified test case identifying the problem:
{code title=flags.cc|borderStyle=solid}
#include <iostream>
#include <ios>
class BadTest
{
public:
BadTest() : _flags(0) { }
~BadTest() { }
unsigned int flags() const { return _flags; }
unsigned int flags (unsigned int f)
{
unsigned int ret = _flags;
_flags |= f;
return ret;
}
unsigned int setf (unsigned int f) { return flags (flags() | f); }
void unsetf (unsigned int f) { flags (flags() & ~f); }
private:
unsigned int _flags;
};
class GoodTest
{
public:
GoodTest() : _flags(0) { }
~GoodTest() { }
unsigned int flags() const { return _flags; }
unsigned int flags (unsigned int f)
{
unsigned int ret = _flags;
_flags |= f;
return ret;
}
unsigned int setf (unsigned int f)
{
unsigned int ret = _flags;
_flags |= f;
return ret;
}
void unsetf (unsigned int f) { _flags &= ~f; }
private:
unsigned int _flags;
};
int main()
{
BadTest bt;
std::ios_base::fmtflags fl;
std::cerr << "***** BadTest *****" << std::endl;
std::cerr << "default flags: " << bt.flags() << std::endl;
fl = std::ios_base::dec;
bt.setf(fl);
std::cerr << "flags: " << bt.flags() << std::endl;
bt.unsetf(fl);
std::cerr << "flags: " << bt.flags() << std::endl;
fl = std::ios_base::hex;
bt.setf(fl);
std::cerr << "flags: " << bt.flags() << std::endl;
bt.unsetf(fl);
std::cerr << "flags: " << bt.flags() << std::endl;
std::cerr << std::endl;
GoodTest gt;
std::cerr << "***** GoodTest *****" << std::endl;
std::cerr << "default flags: " << gt.flags() << std::endl;
fl = std::ios_base::dec;
gt.setf(fl);
std::cerr << "flags: " << gt.flags() << std::endl;
gt.unsetf(fl);
std::cerr << "flags: " << gt.flags() << std::endl;
fl = std::ios_base::hex;
gt.setf(fl);
std::cerr << "flags: " << gt.flags() << std::endl;
gt.unsetf(fl);
std::cerr << "flags: " << gt.flags() << std::endl;
return 0;
}
{code}
1. Output from GCC 4.5.0:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:27:01][1968]>> ./flags-gcc
***** BadTest *****
default flags: 0
flags: 2
flags: 2
flags: 10
flags: 10
***** GoodTest *****
default flags: 0
flags: 2
flags: 0
flags: 8
flags: 0
{noformat}
2. Output from Sun C++ 12.2 with stlport:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:27:05][1969]>> ./flags-ss122-stlport
***** BadTest *****
default flags: 0
flags: 8
flags: 8
flags: 24
flags: 24
***** GoodTest *****
default flags: 0
flags: 8
flags: 0
flags: 16
flags: 0
{noformat}
3. Output from Sun C++ 12.2. with our patched stdcxx:
{noformat}
[steleman@darthvader][/src/steleman/programming/stdcxx-ss122/bugfixes-sunw/fmtflags][02/05/2012
15:27:12][1970]>> ./flags-ss122-stdcxx
***** BadTest *****
default flags: 0
flags: 2
flags: 2
flags: 10
flags: 10
***** GoodTest *****
default flags: 0
flags: 2
flags: 0
flags: 8
flags: 0
{noformat}
The defect is in
{noformat}
std::ios_base::setf(fmtflags fl);
and
std::ios_base::unsetf(fmtflags fl);
{noformat}
in the original stdcxx implementation. The member function
{noformat}
fmtflags std::ios_base::flags() const;
{noformat}
returns by value. Any bitwise operations on the anon temporary created by
this function do not affect the __fmtflags data member of std::ios_base,
which remains unchanged.
Patch for stdcxx 4.2.1 to follow.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
