我目前正在尝试使用boost :: asio编写一些代码，使用clang 3.1进行编译。
我有一个简单的函数对象：
struct tcp_socket_match_condition
{
template <typename TIter>
std::pair<TIter, bool> operator()(TIter begin, TIter end) const
{
auto result(std::find(begin, end, '\n'));
const bool found(result != end);
return std::make_pair(found ? ++result : end, found);
}
};
我尝试将其传递给boost::asio::read_until函数，如下所示：
boost::asio::read_until(socket, stream, match_condition_, error);
生成的编译器错误看起来指出它无法找到正确的函数重载。任何想法为什么这不起作用？
我提供了完整的类和编译器错误。
In file included from src/network/admin_socket.cpp:1:
In file included from include/bytes42/arthur/network/admin_socket.hpp:4:
include/bytes42/arthur/network/tcp_socket.hpp:95:21: error: no matching function for call to 'read_until'
boost::asio::read_until(socket, stream, match_condition_, error);
^~~~~~~~~~~~~~~~~~~~~~~
src/network/admin_socket.cpp:81:10: note: in instantiation of member function
'bytes42::arthur::network::tcp_socket<bytes42::arthur::network::detail::tcp_socket_match_condition>::listen' requested here
socket_.listen();
^
/usr/local/include/boost/asio/impl/read_until.hpp:47:13: note: candidate function [with SyncReadStream =
boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, Allocator =
std::__1::allocator<char>] not viable: no known conversion from 'bytes42::arthur::network::detail::tcp_socket_match_condition' to 'char' for 3rd
argument;
std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:138:13: note: candidate function [with SyncReadStream =
boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, Allocator =
std::__1::allocator<char>] not viable: no known conversion from 'bytes42::arthur::network::detail::tcp_socket_match_condition' to
'const std::string' (aka 'const basic_string<char, char_traits<char>, allocator<char> >') for 3rd argument;
std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:203:13: note: candidate function [with SyncReadStream =
boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, Allocator =
std::__1::allocator<char>] not viable: no known conversion from 'bytes42::arthur::network::detail::tcp_socket_match_condition' to
'const boost::regex' (aka 'const basic_regex<char, regex_traits<char> >') for 3rd argument;
std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:260:13: note: candidate template ignored: substitution failure [with SyncReadStream =
boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, Allocator =
std::__1::allocator<char>, MatchCondition = bytes42::arthur::network::detail::tcp_socket_match_condition]
std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:312:20: note: candidate template ignored: substitution failure [with SyncReadStream =
boost::asio::basic_stream_socket<boost::asio::ip::tcp, boost::asio::stream_socket_service<boost::asio::ip::tcp> >, Allocator =
std::__1::allocator<char>, MatchCondition = bytes42::arthur::network::detail::tcp_socket_match_condition]
inline std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:37:20: note: candidate function template not viable: requires 3 arguments, but 4 were provided
inline std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:93:20: note: candidate function template not viable: requires 3 arguments, but 4 were provided
inline std::size_t read_until(SyncReadStream& s,
^
/usr/local/include/boost/asio/impl/read_until.hpp:193:20: note: candidate function template not viable: requires 3 arguments, but 4 were provided
inline std::size_t read_until(SyncReadStream& s,
^
1 error generated.
make: *** [build/src/network/admin_socket.o] Error 1
类别：
template <typename TMatchCondition>
class tcp_socket
{
public:
typedef std::function<std::string(const std::string&)> data_callback;
public:
tcp_socket(
const unsigned short port,
TMatchCondition match_condition,
data_callback callback);
void listen();
void stop();
private:
tcp_socket(const tcp_socket&) = delete;
tcp_socket(tcp_socket&&) = delete;
tcp_socket& operator=(const tcp_socket&) = delete;
tcp_socket& operator=(tcp_socket&&) = delete;
private:
const utils::entry_exit entry_exit_;
boost::asio::io_service service_;
boost::asio::ip::tcp::acceptor acceptor_;
TMatchCondition match_condition_;
data_callback callback_;
};
template <typename TMatchCondition>
tcp_socket<TMatchCondition>::tcp_socket(
const unsigned short port,
TMatchCondition match_condition,
data_callback callback)
: entry_exit_("tcp_socket:" + std::to_string(port))
, acceptor_(service_, boost::asio::ip::tcp::endpoint(boost::asio::ip::tcp::v4(), port))
, match_condition_(match_condition)
, callback_(callback) {}
template <typename TMatchCondition>
void tcp_socket<TMatchCondition>::listen()
{
const auto port(acceptor_.local_endpoint().port());
const std::string port_str(std::to_string(port));
while(acceptor_.is_open())
{
boost::system::error_code error;
utils::entry_exit ee("Listening on port " + port_str);
boost::asio::ip::tcp::socket socket(service_);
acceptor_.accept(socket, error);
if(error)
{
if(error != boost::asio::error::bad_descriptor)
{
LOG(ERROR)
<< "An error occured while trying to accept a client connection; error="
<< error.message();
sleep(1); // don't want to flood logs
}
}
else
{
while(socket.is_open())
{
boost::asio::streambuf stream;
boost::asio::read_until(socket, stream, match_condition_, error);
const std::string msg(
(std::istreambuf_iterator<char>(&stream)),
std::istreambuf_iterator<char>());
LOG(INFO) << "Received message: " << msg;
boost::asio::write(
socket,
boost::asio::buffer(callback_(msg)),
error);
if(error)
{
if(error != boost::asio::error::broken_pipe)
{
LOG(ERROR)
<< "Error whilst writing response, closing client connection: "
<< error.message();
}
socket.close();
sleep(1); // don't want to flood logs
}
}
}
}
}
template <typename TMatchCondition>
void tcp_socket<TMatchCondition>::stop()
{
boost::system::error_code error;
acceptor_.close(error);
if(error)
{
LOG(ERROR) << "Error whilst stopping TCP socket; error=" << error.message();
}
}
答案 0 :(得分：2)
我认为您没有发布完整的代码，但问题似乎是匹配条件：您是否使用boost::is_match_condition指定您的tcp_socket_match_condition是匹配条件？
答案 1 :(得分：1)
确定;所以clang在这里（有点）很有帮助。
它告诉你read_until有 8个特化，并且它们无法使它们工作。
前三个接受char，char和std :: string作为第三个参数。那不行。
最后三个有三个参数 - 你通过四个。那些穿着也不起作用。
这使得两个人处于中间位置。出于某种原因，您的TMatchCondition正在产生替代失败。
正如Dietmar刚刚指出的那样，你一定要检查boost::is_match_condition<TMatchCondition>::value是否属实 - 因为如果不是这样的话就行不通。