c++ - 由于对 callcc 的调用不明确，Boost 协程无法编译

Question

我正在尝试在工作中的 C++ 项目中使用协程。但是，由于 callcc() 的使用不明确，它不会编译。我已经尝试在协程构造函数中指定分配器，但这似乎没有什么不同。

在将代码剥离到最基本的部分后，我最终用与 boost 文档中的斐波那契示例非常相似的东西重现了这个问题。

#include <iostream>
#include <boost/coroutine2/all.hpp>

/*
    c++ -std=c++11 -o corofib corofib.cpp
*/

typedef boost::coroutines2::coroutine<unsigned long> coro_t;

coro_t::pull_type generator(
    [](coro_t::push_type& sink) {
        unsigned long first = 1L;
        unsigned long second = 1L;
        unsigned long answer;

        sink(first);
        sink(second);
        while(1) {
            answer = first + second;
            first = second;
            second = answer;
            sink(answer);
        };
    }
);


int main(int argc, char* argv[]) {
    generator();
    std::cout << generator.get() << std::endl;
    generator();
    std::cout << generator.get() << std::endl;
    generator();
    std::cout << generator.get() << std::endl;
    generator();
    std::cout << generator.get() << std::endl;
}

我正在使用:

• boost 1.64
• gcc 版本 4.9.2
• Linux delegato 3.16.0-4-amd64 #1 SMPDebian 3.16.39-1+deb8u2 (2017-03-07) x86_64 GNU/Linux

这是我收到的错误消息。我已经删除了“required from”通知以试图缩短这篇文章:

lear@delegato:~/lamu$ c++ -std=c++14 -o corofib corofib.cpp
In file included from /usr/local/include/boost/coroutine2/detail/coroutine.hpp:48:0,
                 from /usr/local/include/boost/coroutine2/coroutine.hpp:15,
                 from /usr/local/include/boost/coroutine2/all.hpp:10,
                 from corofib.cpp:2:
/usr/local/include/boost/coroutine2/detail/pull_control_block_cc.ipp: In instantiation of ‘boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]’:
/usr/local/include/boost/coroutine2/detail/pull_control_block_cc.ipp:105:14: error: call of overloaded ‘callcc(const std::allocator_arg_t&, boost::context::preallocated&, boost::context::basic_fixedsize_stack<boost::context::stack_traits>&, boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]::<lambda(boost::context::continuation&&)>)’ is ambiguous
             });
              ^
/usr/local/include/boost/coroutine2/detail/pull_control_block_cc.ipp:105:14: note: candidates are:
In file included from /usr/local/include/boost/coroutine2/detail/pull_control_block_cc.hpp:14:0,
                 from /usr/local/include/boost/coroutine2/detail/coroutine.hpp:37,
                 from /usr/local/include/boost/coroutine2/coroutine.hpp:15,
                 from /usr/local/include/boost/coroutine2/all.hpp:10,
                 from corofib.cpp:2:
/usr/local/include/boost/context/continuation.hpp:469:1: note: boost::context::continuation boost::context::callcc(std::allocator_arg_t, StackAlloc, Fn&&, Arg ...) [with StackAlloc = boost::context::preallocated; Fn = boost::context::basic_fixedsize_stack<boost::context::stack_traits>&; Arg = {boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]::<lambda(boost::context::continuation&&)>}]
 callcc( std::allocator_arg_t, StackAlloc salloc, Fn && fn, Arg ... arg) {
 ^
/usr/local/include/boost/context/continuation.hpp:483:1: note: boost::context::continuation boost::context::callcc(std::allocator_arg_t, boost::context::preallocated, StackAlloc, Fn&&, Arg ...) [with StackAlloc = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]::<lambda(boost::context::continuation&&)>; Arg = {}]
 callcc( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn, Arg ... arg) {
 ^
/usr/local/include/boost/context/continuation.hpp:514:1: note: boost::context::continuation boost::context::callcc(std::allocator_arg_t, boost::context::preallocated, StackAlloc, Fn&&) [with StackAlloc = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]::<lambda(boost::context::continuation&&)>]
 callcc( std::allocator_arg_t, preallocated palloc, StackAlloc salloc, Fn && fn) {
 ^
/usr/local/include/boost/context/continuation.hpp:457:1: note: boost::context::continuation boost::context::callcc(Fn&&, Arg ...) [with Fn = const std::allocator_arg_t&; Arg = {boost::context::preallocated, boost::context::basic_fixedsize_stack<boost::context::stack_traits>, boost::coroutines2::detail::pull_coroutine<T>::control_block::control_block(boost::context::preallocated, StackAllocator, Fn&&) [with StackAllocator = boost::context::basic_fixedsize_stack<boost::context::stack_traits>; Fn = <lambda(boost::coroutines2::coroutine<long unsigned int>::push_type&)>; T = long unsigned int]::<lambda(boost::context::continuation&&)>}; <template-parameter-1-3> = void]
 callcc( Fn && fn, Arg ... arg) {

我认为代码基本上是合理的:我只需要以某种方式消除歧义。

我可以说说这在 python 中是多么容易，但它可能会引起笑声。

Answer 1

这是 Boost.Context 中的一个错误，它是 reported和 fixed上游的。您可以找到专门针对 Boost 1.64 的补丁 here .