模板和lambda与Clang的编译错误

I was trying to compile a project with a code that looks like this

我试图使用看起来像这样的代码编译项目

#include <tuple>
#include <utility>

struct Foo
{
};

template <typename... Args>
void start(Args&&... args) {
    auto x = [args = std::make_tuple(std::forward<Args>(args)...)] () mutable {
            auto y = [args] () mutable {
                auto z = [] (Args&&... args) {
                    return new Foo(std::forward<Args>(args)...);
                };
            };
    };
}

int main()
{
    start(Foo{});
}

It seems to compile fine in GCC 4.9.1 but not in Clang 3.4, 3.5, 3.6. The error message is

似乎在GCC 4.9.1中编译良好,但在Clang 3.4,3.5,3.6中没有编译。错误消息是

error: variable 'args' cannot be implicitly captured in a lambda with no capture-default specified

错误:变量'args'不能在没有指定capture-default的lambda中隐式捕获

Is it a compiler bug? If so, is there any workaround to get it to compile on Clang?

这是编译器错误吗?如果是这样,是否有任何解决方法让它在Clang上编译?

1 个解决方案

#1

Reduced to:

template <typename T>
void start(T t) {
    [a = t] { [a]{}; };
}

int main()
{
    start(0);
}

Which generates the same error in non-trunk versions of clang.

这在clang的非主干版本中会产生相同的错误。

This appears to be caused by a bug in Clang's handling of a non-init-capture of an init-capture. Said bug was fixed yesterday, May 7, and the current trunk version of Clang compiles the code above correctly.

这似乎是由Clang处理init-capture的非初始捕获错误引起的。昨天,5月7日修复了错误,当前的Clang主干版本正确编译了上面的代码。

Since this bug only manifests for non-init-captures of init-captures, a simple workaround is to use an init-capture in the inner lambda as well - instead of [a], do [a = a].

由于此错误仅表示init-capture的非初始捕获,因此一个简单的解决方法是在内部lambda中使用init-capture - 而不是[a],执行[a = a]。

#1