模板模板参数和。 [英] template template parameters and clang
问题描述
我有问题（可能是我的）与模板模板参数和铛。下面的玩具示例在g ++ 4.7.0下编译和运行，而不是clang ++ 3.0（基于LLVM 3.0），都是ubuntu 12.04。
I have had problems (possibly mine) with template template parameters and clang. The following toy example compiles and runs under g++ 4.7.0, not clang++ 3.0 (based on LLVM 3.0), both ubuntu 12.04.
玩具示例
#include <iostream>
#include <memory>
struct AFn
{
void operator()()
{
; // do something
}
};
template<typename T>
struct impl
{
T *backpointer_;
};
template<typename S, template <typename> class T>
struct implT
{
T<S> *backpointer_;
};
template<typename>
class AClass;
template<>
struct implT<AFn, AClass>
{
implT(std::string message) :
message_(message)
{}
void operator()()
{
std::cout << " : " << message_ << std::endl;
}
std::string message_;
};
template<typename Fn>
class AClass
{
private:
std::shared_ptr<implT<Fn, AClass> > p_;
public:
AClass(std::string message) :
p_(std::make_shared<implT<Fn, AClass> >(message))
{}
void call_me()
{
p_->operator()();
}
};
int main(int argc, char **argv)
{
AClass<AFn> *A = new AClass<AFn>("AClass<AFn>");
A->call_me();
delete A;
return 0;
}
clang输出：
*****@ely:~$ clang++ -std=c++11 test_1.cpp -o test_1
test_1.cpp:47:30: error: template argument for template template parameter must be a class template or
type alias template
std::shared_ptr<implT<Fn, AClass> > p_;
^
test_1.cpp:47:40: error: C++ requires a type specifier for all declarations
std::shared_ptr<implT<Fn, AClass> > p_;
^~
test_1.cpp:50:36: error: template argument for template template parameter must be a class template or
type alias template
p_(std::make_shared<implT<Fn, AClass> >(message))
^
3 errors generated.
I can't make sense of the first error. It compiles and runs fine with gcc/g++ 4.7.0. Any help would be appreciated.
推荐答案
如上所述，这是一个Clang错误。 AClass 有一个 inject-class-name ，这是一个独特的语法结构，既是一个 class-name
As noted, it's a Clang bug. AClass there is an injected-class-name, a unique grammatical construct which is both a class-name and a template-name.
另一个解决方法是说 AClass :: template AClass 。这避免需要用其包围的命名空间限定 AClass 。
Another workaround is to say AClass::template AClass. This avoids needing to qualify AClass with its enclosing namespace.
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