libstdc++/9521: Garbled input from wcin
peturr02@ru.is
peturr02@ru.is
Fri Jan 31 13:07:00 GMT 2003
>Number: 9521
>Category: libstdc++
>Synopsis: Garbled input from wcin
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Fri Jan 31 12:16:01 UTC 2003
>Closed-Date:
>Last-Modified:
>Originator: peturr02@ru.is
>Release: gcc-3.2.1
>Organization:
>Environment:
Red Hat Linux 8.0
>Description:
If wcin.rdbuf()->sgetc() is called followed by wcin.rdbuf()->sbumpc(), the return value is not always the same, unless the charset in use happens to be ISO-8859-1.
Reason: basic_filebuf<wchar_t>::_M_underflow_common returns wide characters to the FILE* using ungetc. This happens to work if the charset is ISO-8859-1 (because the values are the same as in UCS-4), but breaks for all other single-byte charsets.
Note that there is an even more serious bug here when dealing with multibyte charsets: in general a single wide character can have been converted from more than one narrow character. This is however shadowed by other problems in _M_underflow_common.
>How-To-Repeat:
See attachment.
>Fix:
>Release-Note:
>Audit-Trail:
>Unformatted:
----gnatsweb-attachment----
Content-Type: text/plain; name="ungetcbug.cc"
Content-Disposition: inline; filename="ungetcbug.cc"
#include <iostream>
#include <fstream>
#include <locale>
#include <cwchar>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
int main()
{
using namespace std;
const char* name = "tmp";
filebuf fbuf1;
fbuf1.open(name, ios_base::out | ios_base::trunc);
for (int i = 1; i < 256; ++i)
fbuf1.sputc(static_cast<unsigned char>(i));
fbuf1.close();
int fd = open(name, O_RDONLY);
assert(fd != -1);
dup2(fd, 0);
locale loc ("en_US.ISO-8859-15");
locale::global(loc);
wcin.imbue(loc);
for (int j = 1; j < 256; ++j)
{
wint_t c1 = wcin.rdbuf()->sgetc();
wint_t c2 = wcin.rdbuf()->sbumpc();
assert(c1 == c2);
assert(c1 != WEOF);
}
return 0;
}
More information about the Gcc-bugs
mailing list