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Re: libstdc++/1704
- To: bkoz at gcc dot gnu dot org
- Subject: Re: libstdc++/1704
- From: Paolo Carlini <pcarlini at unitus dot it>
- Date: 28 May 2001 13:16:04 -0000
- Cc: gcc-prs at gcc dot gnu dot org,
- Reply-To: Paolo Carlini <pcarlini at unitus dot it>
The following reply was made to PR libstdc++/1704; it has been noted by GNATS.
From: Paolo Carlini <pcarlini@unitus.it>
To: bkoz@gcc.gnu.org
Cc: nicolai.josuttis@braunschweig.netsurf.de, bkoz@redhat.com,
gcc-gnats@gcc.gnu.org, nobody@gcc.gnu.org
Subject: Re: libstdc++/1704
Date: Mon, 28 May 2001 15:11:36 +0200
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Hi,
so, I understand from your detailed analysis that this is just a QoI issue?
Honestly, as a beginner C++ programmer I slightly prefer the solution adopted by STLport: a conversion error is issued at compile time. Otherwise I find this kind of programming errors *very* difficult to debug ...
Thanks,
Paolo Carlini.
bkoz@gcc.gnu.org wrote:
> Synopsis: Null output from Josuttis example
>
> Responsible-Changed-From-To: unassigned->bkoz
> Responsible-Changed-By: bkoz
> Responsible-Changed-When: Fri May 25 11:33:14 2001
> Responsible-Changed-Why:
> Mine.
> State-Changed-From-To: analyzed->feedback
> State-Changed-By: bkoz
> State-Changed-When: Fri May 25 11:33:14 2001
> State-Changed-Why:
> I don't thing this is a bug, really.
> In particular,
> c = std::toupper(c, getloc());
>
> where c == int_type attempts to instantiate
>
> template<typename _CharT>
> inline _CharT
> toupper(_CharT __c, const locale& __loc)
> { return use_facet<ctype<_CharT> >(__loc).toupper(__c); }
>
> with _CharT == int. This is allowed, but keep in mind that the standard locale doesn't have ctype<int> as a standard facet, so thus use_facet has to fail:
>
> template<typename _Facet>
> const _Facet&
> use_facet(const locale& __loc)
> {
> typedef locale::_Impl::__vec_facet __vec_facet;
> size_t __i = _Facet::id._M_index;
> __vec_facet* __facet = __loc._M_impl->_M_facets;
> const locale::facet* __fp = (*__facet)[__i];
> if (__fp == 0 || __i >= __facet->size())
> __throw_bad_cast();
> return static_cast<const _Facet&>(*__fp);
> }
>
>
> So, std::bad_cast gets thrown here. This is, I believe, standard conformant behavior. To use ctype<int>, you'd have to imbue it in the standard locale (and then add some kind of ctype<int> functionality, which is of course a bit of a job.)
>
> Instead, I suggest casting the argument to toupper to either char or wchart_t, so that the standard ctype facets are used. I suspect this is the intent of the code.
>
> Nico?
>
> -benjamin
>
>
> class outbuf : public std::streambuf
> {
> protected:
> virtual int_type overflow(int_type c)
> {
> if (c != EOF)
> {
> // convert lowercase to uppercase
> try
> {
> // c = std::toupper(static_cast<char>(c), getloc());
> c = std::toupper(c, getloc());
> }
> catch (std::exception& obj)
> {
> puts("trying to use ctype<int> in a locale that doesn't have it");
> }
>
> // and write the character to the standard output
> if (std::putchar(c) == EOF)
> return EOF;
> }
> return c;
> }
> };
>
> http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=1704&database=gcc
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<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
Hi,
<p>so, I understand from your detailed analysis that this is just a QoI
issue?
<br>Honestly, as a beginner C++ programmer I slightly prefer the solution
adopted by STLport: a conversion error is issued at compile time. Otherwise
I find this kind of programming errors *very* difficult to debug ...
<p>Thanks,
<br>Paolo Carlini.
<br>
<p>bkoz@gcc.gnu.org wrote:
<blockquote TYPE=CITE>Synopsis: Null output from Josuttis example
<p>Responsible-Changed-From-To: unassigned->bkoz
<br>Responsible-Changed-By: bkoz
<br>Responsible-Changed-When: Fri May 25 11:33:14 2001
<br>Responsible-Changed-Why:
<br> Mine.
<br>State-Changed-From-To: analyzed->feedback
<br>State-Changed-By: bkoz
<br>State-Changed-When: Fri May 25 11:33:14 2001
<br>State-Changed-Why:
<br> I don't thing this is a bug, really.
<br> In particular,
<br> c = std::toupper(c, getloc());
<p> where c == int_type attempts to instantiate
<p> template<typename _CharT>
<br> inline _CharT
<br> toupper(_CharT __c, const
locale& __loc)
<br> { return use_facet<ctype<_CharT>
>(__loc).toupper(__c); }
<p> with _CharT == int. This is allowed, but keep in
mind that the standard locale doesn't have ctype<int> as a standard
facet, so thus use_facet has to fail:
<p> template<typename _Facet>
<br> const _Facet&
<br> use_facet(const locale&
__loc)
<br> {
<br> typedef locale::_Impl::__vec_facet
__vec_facet;
<br> size_t __i =
_Facet::id._M_index;
<br> __vec_facet*
__facet = __loc._M_impl->_M_facets;
<br> const locale::facet*
__fp = (*__facet)[__i];
<br> if (__fp ==
0 || __i >= __facet->size())
<br>
__throw_bad_cast();
<br> return static_cast<const
_Facet&>(*__fp);
<br> }
<br>
<p> So, std::bad_cast gets thrown here. This is, I believe,
standard conformant behavior. To use ctype<int>, you'd have to imbue
it in the standard locale (and then add some kind of ctype<int> functionality,
which is of course a bit of a job.)
<p> Instead, I suggest casting the argument to toupper
to either char or wchart_t, so that the standard ctype facets are used.
I suspect this is the intent of the code.
<p> Nico?
<p> -benjamin
<br>
<p> class outbuf : public std::streambuf
<br> {
<br> protected:
<br> virtual int_type overflow(int_type c)
<br> {
<br> if (c != EOF)
<br> {
<br> // convert lowercase to
uppercase
<br> try
<br> {
<br>
// c = std::toupper(static_cast<char>(c),
getloc());
<br>
c = std::toupper(c, getloc());
<br> }
<br> catch (std::exception&
obj)
<br> {
<br>
puts("trying to use ctype<int> in a locale that doesn't have it");
<br> }
<p> // and write the character
to the standard output
<br> if (std::putchar(c) == EOF)
<br> return EOF;
<br> }
<br> return c;
<br> }
<br> };
<p><a href="http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=1704&database=gcc";>http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view&pr=1704&database=gcc</a></blockquote>
<br> </html>
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