libstdc++/9169: filebuf output fails if codecvt<>::out returns noconv

[peturr02 at ru dot is]

>Number:         9169
>Category:       libstdc++
>Synopsis:       filebuf output fails if codecvt<>::out returns noconv
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    unassigned
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Sat Jan 04 02:26:00 PST 2003
>Closed-Date:
>Last-Modified:
>Originator:     peturr02@ru.is
>Release:        gcc-3.2.1
>Organization:
>Environment:
Red Hat Linux 8.0
>Description:
If a codecvt<char, char, mbstate_t> facet that returns false from always_noconv(), but returns noconv from out() is installed in a filebuf, no output is produced.
>How-To-Repeat:
See attachment.
>Fix:

>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="noconvout.cc"
Content-Disposition: inline; filename="noconvout.cc"

#include <locale>
#include <algorithm>
#include <cstddef>
#include <cstdio>
#include <string>
#include <fstream>
#include <iostream>
using namespace std;

class Cvt_to_upper : public codecvt<char, char, mbstate_t>
{
	typedef codecvt<char, char, mbstate_t> Base;

public:
	explicit Cvt_to_upper(size_t refs = 0)
		: Base(refs)
		{
		}

protected:
	result do_in(state_type&,
		     const extern_type* from, const extern_type* from_end,
		     const extern_type*& from_next,
		     intern_type* to, intern_type* to_end,
		     intern_type*& to_next) const
		{
			while (from < from_end && to < to_end)
				*to++ = toupper(*from++);

			to_next = to;
			from_next = from;
			return from == from_end ? ok : partial;
		}

	bool do_always_noconv() const throw()
		{
			return false;
		}
};

int main()
{
	locale loc1;
	locale loc (loc1, new Cvt_to_upper);
	
	char name[] = "noconvXXXXXX";
	mktemp(name);

	string str ("abcdefghijklmnopqrstuvwxyz");
	string tmp;

	{
		ofstream out;
		out.imbue(loc);
		out.open(name);
		copy(str.begin(), str.end(),
		     ostreambuf_iterator<char>(out));
	}
	{
		ifstream in;
		in.open(name);
		copy(istreambuf_iterator<char>(in),
		     istreambuf_iterator<char>(),
		     back_inserter(tmp));
	}

	remove(name);

	cout << tmp << endl;
	assert(tmp.size() == str.size());
	assert(tmp == str);

	return 0;
}