* [Bug c++/26950] Error diagnostic not issued for unacceptable result of lookup for a name used in a nested-name-specifier
2006-03-30 19:20 [Bug c++/26950] New: " widman at gimpel dot com
@ 2006-03-30 20:02 ` pinskia at gcc dot gnu dot org
2006-03-30 21:06 ` widman at gimpel dot com
` (3 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: pinskia at gcc dot gnu dot org @ 2006-03-30 20:02 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from pinskia at gcc dot gnu dot org 2006-03-30 20:02 -------
Hmm, Comeau C++ does not reject this code either (but that does not mean this
is not invalid code).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug c++/26950] Error diagnostic not issued for unacceptable result of lookup for a name used in a nested-name-specifier
2006-03-30 19:20 [Bug c++/26950] New: " widman at gimpel dot com
2006-03-30 20:02 ` [Bug c++/26950] " pinskia at gcc dot gnu dot org
@ 2006-03-30 21:06 ` widman at gimpel dot com
2006-03-30 23:31 ` widman at gimpel dot com
` (2 subsequent siblings)
4 siblings, 0 replies; 8+ messages in thread
From: widman at gimpel dot com @ 2006-03-30 21:06 UTC (permalink / raw)
To: gcc-bugs
------- Comment #2 from widman at gimpel dot com 2006-03-30 21:06 -------
Subject: Error diagnostic not issued for unacceptable result of lookup for a
name used in a nested-name-specifier
On Mar 30, 2006, at 2:56 PM, Daveed Vandevoorde wrote:
> Hi James,
>
> On Mar 30, 2006, at 2:31 PM, James Widman wrote:
>
>> [This can probably also be categorized as "low priority".]
>>
>> The GCC and EDG front ends both appear to think that this test
>> case is well-formed:
>>
>> namespace N {
>> const int a = 42;
>> enum N { e0 = N::a };
>> }
>>
>> ... but I think 3.4.3p1 makes it ill-formed.
>
>
> Can you elaborate on that? 3.4.3/1 says:
>
> The name of a class or namespace member can be referred to
> after the :: scope resolution operator (5.1) applied to a
> nested-name-specifier that nominates its class or namespace.
> During the lookup for a name preceding the :: scope resolution
> operator, object, function, and enumerator names are ignored.
> If the name found is not a class-name (clause 9) or
> namespace-name (7.3.1), the program is ill-formed.
>
> So when looking up N in N::a, the "enum N" entry is ignored, and the
> "namespace N" entry is found. "a" is a member of that namespace, and
> it can be used in an integral constant-expression.
>
> Am I missing something?
>
> Daveed Vandevoorde
> Edison Design Group
"enum N" is not an enumerator name; it's an enumeration name (or an /
enum-name/ [7.2p1]), so "enum N" cannot be ignored.
In C (ignoring the namespace N for now), we would say that the
enumeration name N resides in the tag name space (along with the tag
names of structs and unions) and e0 resides in the ordinary name
space (along with the names of functions, variables, and typedef
names -- see C89: 3.1.2.3, C99:6.2.3).
So when I read that excerpt of 3.4.3/1, I thought to myself:
"During the lookup for a name preceding the :: scope resolution
operator, ordinary names are ignored, except that typedef names and
namespace names are considered."
... with the implication being that tag names (including the names of
classes, unions, and enumerations) are considered without exception.
>> I also reported this to:
>>
>> http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
>>
>> MSVC (6 through 8) and Borland 5.6 appear to treat the enum-name
>> as hiding the namespace name during lookup for the nested-name-
>> specifier.
>>
>> James Widman
>> --
>> Gimpel Software
>> http://gimpel.com
>>
>>
>
James Widman
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug c++/26950] Error diagnostic not issued for unacceptable result of lookup for a name used in a nested-name-specifier
2006-03-30 19:20 [Bug c++/26950] New: " widman at gimpel dot com
2006-03-30 20:02 ` [Bug c++/26950] " pinskia at gcc dot gnu dot org
2006-03-30 21:06 ` widman at gimpel dot com
@ 2006-03-30 23:31 ` widman at gimpel dot com
2006-03-31 5:36 ` widman at gimpel dot com
2008-02-10 14:09 ` manu at gcc dot gnu dot org
4 siblings, 0 replies; 8+ messages in thread
From: widman at gimpel dot com @ 2006-03-30 23:31 UTC (permalink / raw)
To: gcc-bugs
------- Comment #3 from widman at gimpel dot com 2006-03-30 23:31 -------
Subject: Re: Error diagnostic not issued for unacceptable result of lookup for
a name used in a nested-name-specifier
On Mar 30, 2006, at 4:06 PM, widman at gimpel dot com wrote:
> <snip>
> So when I read that excerpt of 3.4.3/1, I thought to myself:
>
> "During the lookup for a name preceding the :: scope resolution
> operator, ordinary names are ignored, except that typedef names and
> namespace names are considered."
>
> ... with the implication being that tag names (including the names of
> classes, unions, and enumerations) are considered without exception.
What was the intention in 3.4.3p1? Presumably it's to prevent lookup
from finding names that don't refer to namespaces or classes. If
that's the case then we probably want a change in wording here --
maybe something like:
During the lookup for a name preceding the ::
scope resolution operator, only the following
kinds of names are considered:
- class-names,
- class template names (when used to form
a template-id),
- namespace names, and
- typedef names
All other names are ignored. If the name
found does not designate:
- a class,
- a dependent type that could possibly
refer to a class during instantiation,
or
- a namespace,
then the program is ill-formed. If the name
designates a dependent type, no diagnostic is
required.
(See also http://www.open-std.org/jtc1/sc22/wg21/docs/
cwg_active.html, item 215)
James Widman
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug c++/26950] Error diagnostic not issued for unacceptable result of lookup for a name used in a nested-name-specifier
2006-03-30 19:20 [Bug c++/26950] New: " widman at gimpel dot com
` (2 preceding siblings ...)
2006-03-30 23:31 ` widman at gimpel dot com
@ 2006-03-31 5:36 ` widman at gimpel dot com
2008-02-10 14:09 ` manu at gcc dot gnu dot org
4 siblings, 0 replies; 8+ messages in thread
From: widman at gimpel dot com @ 2006-03-31 5:36 UTC (permalink / raw)
To: gcc-bugs
------- Comment #4 from widman at gimpel dot com 2006-03-31 05:36 -------
Subject: Re: Error diagnostic not issued for unacceptable result of lookup for
a name used in a nested-name-specifier
On Mar 30, 2006, at 11:47 PM, Daveed Vandevoorde wrote:
>
> On Mar 30, 2006, at 4:06 PM, James Widman wrote:
<snip>
>> "enum N" is not an enumerator name; it's an enumeration name (or
>> an /enum-name/ [7.2p1]), so "enum N" cannot be ignored.
>
> Ah, you're right. It turns out that the grammar in this area
> has changed since the 1998 standard (as John Spicer pointed
> out to me). The 1998 version of the standard had
>
> nested-name-specifier:
> class-or-namespace-name :: nested-name-specifieropt
> class-or-namespace-name :: template nested-name-specifier
>
> which meant only classes or namespace names were considered.
> That could be read as meaning that 3.4.3/1 never was reached
> with an enumeration type name, but there is no unanimity on
> that reading.
>
> With the current wording (which was introduced because the
> earlier wording didn't correctly deal with template-dependent
> qualifiers), it's pretty unambiguous that your example is
> ill-formed and we think the standard should not be changed
> in that regard.
>
> I've filed a defect numbered EDGcpfe/7621 to track this.
>
> Cheers,
>
> Daveed Vandevoorde
> Edison Design Group
Thanks; that should help to simplify our lookup routines ever-so-
slightly. (:
For those with a superstitious bent, I'd like to point out that this
week saw a total eclipse of the sun, news of genetically modified
pigs (perhaps with wings next), and now it's been revealed that GCC
and EDG have the same front end bug for a case where *every other C++
front end* appears to get it right.
This is clearly a sign that the end is nigh. It's apocalypse party
time. (:
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
^ permalink raw reply [flat|nested] 8+ messages in thread* [Bug c++/26950] Error diagnostic not issued for unacceptable result of lookup for a name used in a nested-name-specifier
2006-03-30 19:20 [Bug c++/26950] New: " widman at gimpel dot com
` (3 preceding siblings ...)
2006-03-31 5:36 ` widman at gimpel dot com
@ 2008-02-10 14:09 ` manu at gcc dot gnu dot org
4 siblings, 0 replies; 8+ messages in thread
From: manu at gcc dot gnu dot org @ 2008-02-10 14:09 UTC (permalink / raw)
To: gcc-bugs
------- Comment #5 from manu at gcc dot gnu dot org 2008-02-10 14:08 -------
Confirmed in g++ 4.3.
--
manu at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |manu at gcc dot gnu dot org
Status|UNCONFIRMED |NEW
Ever Confirmed|0 |1
Keywords| |accepts-invalid
Known to fail| |4.3.0
Last reconfirmed|0000-00-00 00:00:00 |2008-02-10 14:08:42
date| |
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=26950
^ permalink raw reply [flat|nested] 8+ messages in thread