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* c++/6327: g++ problems where partial specializing nested templates
@ 2002-04-16 10:16 cuni
0 siblings, 0 replies; 2+ messages in thread
From: cuni @ 2002-04-16 10:16 UTC (permalink / raw)
To: gcc-gnats
>Number: 6327
>Category: c++
>Synopsis: g++ problems where partial specializing nested templates
>Confidential: no
>Severity: serious
>Priority: medium
>Responsible: unassigned
>State: open
>Class: sw-bug
>Submitter-Id: net
>Arrival-Date: Tue Apr 16 10:16:01 PDT 2002
>Closed-Date:
>Last-Modified:
>Originator: g++
>Release: Thread model: single - gcc version 3.0
>Organization:
>Environment:
Mandrake 8.0 on AMD Athlon 800
>Description:
It seems that the compiler doesn't use correctly partial specialization of a nested template, even if it produce correct code when template are not nested.
>How-To-Repeat:
#include <typeinfo>
#include <iostream>
// generic template
template<class T>
struct Array_traits
{
template<class U>
struct Rebind
{
typedef U Type;
};
};
// partial specialization for arrays
template<class T, int N>
struct Array_traits<T[N]>
{
template<class U>
struct Rebind
{
typedef Array_traits<T>::Rebind<U>::Type Type[N];
};
};
int main()
{
typedef int array_of_int[10][20][30];
Array_traits<array_of_int>::Rebind<float>::Type array_of_float;
// it prints out A10_A20_A30_i
std::cout << typeid(array_of_int).name() << std::endl;
// it should print A10_A20_A30_f, but it prints A10_f
std::cout << typeid(array_of_float).name() << std::endl;
}
>Fix:
Here is a work-around that doesn't use nested templates:
// generic template
template<class T, class U>
struct Array_rebind
{
typedef U Type;
};
// partial specialization
template<class T, int N, class U>
struct Array_rebind<T[N], U>
{
typedef Array_rebind<T,U>::Type Type[N];
};
>Release-Note:
>Audit-Trail:
>Unformatted:
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: c++/6327: g++ problems where partial specializing nested templates
@ 2002-04-16 18:51 rodrigc
0 siblings, 0 replies; 2+ messages in thread
From: rodrigc @ 2002-04-16 18:51 UTC (permalink / raw)
To: cuni, gcc-bugs, gcc-prs, nobody
Synopsis: g++ problems where partial specializing nested templates
State-Changed-From-To: open->closed
State-Changed-By: rodrigc
State-Changed-When: Tue Apr 16 18:51:13 2002
State-Changed-Why:
Compiles OK with gcc 3.0.4.
With gcc 3.1 (prerelease) there are some warnings, but
it still compiles:
a.cc:18: warning: `typename Array_traits<T>::Rebind<U>::Type' is implicitly a
typename
a.cc:18: warning: implicit typename is deprecated, please see the documentation
for details
http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&database=gcc&pr=6327
^ permalink raw reply [flat|nested] 2+ messages in thread
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