非命名空间范围内的显式专业化无法在GCC中进行编译 [英] Explicit specialization in non-namespace scope does not compile in GCC

问题描述

以下代码在Clang中编译，但不在GCC中编译:

The following code compiles in Clang but does not in GCC:

template<typename T>
struct Widget
{
    template<typename U>
    void foo(U)
    {
    }

    template<>
    void foo(int*)
    {
    }
};

根据C ++标准([temp.expl.spec]，第2段):

According to the C++ standard ([temp.expl.spec], paragraph 2):

可以在可以使用相应主模板的任何范围内声明显式专业化 定义

An explicit specialization may be declared in any scope in which the corresponding primary template may be defined

这是GCC中的错误吗?如果是的话，如何在其错误跟踪器中找到它?

Is this a bug in GCC and if so how can I find it in its bug tracker?

这是GCC的输出:

prog.cc:13:14: error: explicit specialization in non-namespace scope 'struct Widget<T>'
     template<>
              ^

我正在使用带有-std=c++2a的GCC HEAD 8.0.1.

I'm using GCC HEAD 8.0.1, with -std=c++2a.

推荐答案

这应该是GCC错误.完全专业化应允许在任何范围内使用，包括在类定义中使用.

This should be a GCC bug. Full specialization should be allowed in any scope, including in class definition.

根据 CWG 727 ，[临时expl.spec]第2段从

According to CWG 727, [temp.expl.spec] paragraph 2 was changed from

(重点是我的)

显式专门化必须在包含专门化模板的命名空间中声明.声明符-id或class-head-name不合格的显式专门化应在模板的最近封闭名称空间中声明，或者，如果该名称空间是内联(10.3.1 [namespace.def])，则应在其模板中声明任何名称空间.封闭名称空间集.这样的声明也可以是定义.如果声明不是定义，则可以稍后定义专门化(10.3.1.2 [namespace.memdef]).

An explicit specialization shall be declared in a namespace enclosing the specialized template. An explicit specialization whose declarator-id or class-head-name is not qualified shall be declared in the nearest enclosing namespace of the template, or, if the namespace is inline (10.3.1 [namespace.def]), any namespace from its enclosing namespace set. Such a declaration may also be a definition. If the declaration is not a definition, the specialization may be defined later (10.3.1.2 [namespace.memdef]).

到

(重点是我的)

可以在可以定义相应主模板的任何范围内声明显式专业化()(10.3.1.2 [namespace.memdef]，12.2 [class.mem]，17.6.2 [temp .mem]).

An explicit specialization may be declared in any scope in which the corresponding primary template may be defined (10.3.1.2 [namespace.memdef], 12.2 [class.mem], 17.6.2 [temp.mem]).

GCC似乎无法遵循.

It seems GCC fails to follow this.

编辑

我将此问题报告为错误85282 .

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