Question

以下示例导致：

boost / bind / bind.hpp：882：错误：返回对临时的引用

如果使用-std = c ++ 0x编译。

如果在没有-std = c ++ 0x标志的情况下构建，则不会发生警告。似乎boost试图在这里使用c ++ 11 rvalues，即使gcc 4.4不完全支持它。提前谢谢！

gcc version 4.4.7 20120313（Red Hat 4.4.7-17）（GCC）

完整构建线： g ++ -std = c ++ 0x -Wall -Werror -I / pathtoboost / include main.cpp -o bind

#include <boost/function.hpp>
#include <boost/bind.hpp>

#include <iostream>

int foo( int a )
{
    std::cout << "a: " << a << std::endl;
    return a;
}

int main( int argc, char** argv )
{
    foo( 5 );
    boost::function< int( int ) > bfoo = boost::bind( foo, _1 );
    bfoo( 10 );
    return 0;
}

完整版本错误（警告）：

cc1plus: warnings being treated as errors
In file included from /boost/include/boost/bind.hpp:22,
                 from main.cpp:2:
/boost/include/boost/bind/bind.hpp: In member function ‘A1&& boost::_bi::rrlist1<A1>::operator[](boost::arg<1> (*)()) const [with A1 = int]’:
/boost/include/boost/bind/bind.hpp:249:   instantiated from ‘R boost::_bi::list1<A1>::operator()(boost::_bi::type<R>, F&, A&, long int) [with R = int, F = int (*)(int), A = boost::_bi::rrlist1<int>, A1 = boost::arg<1>]’
/boost/include/boost/bind/bind.hpp:1306:   instantiated from ‘typename boost::_bi::result_traits<R, F>::type boost::_bi::bind_t<R, F, L>::operator()(A1&&) [with A1 = int, R = int, F = int (*)(int), L = boost::_bi::list1<boost::arg<1> >]’
/boost/include/boost/function/function_template.hpp:138:   instantiated from ‘static R boost::detail::function::function_obj_invoker1<FunctionObj, R, T0>::invoke(boost::detail::function::function_buffer&, T0) [with FunctionObj = boost::_bi::bind_t<int, int (*)(int), boost::_bi::list1<boost::arg<1> > >, R = int, T0 = int]’
/boost/include/boost/function/function_template.hpp:925:   instantiated from ‘void boost::function1<R, T1>::assign_to(Functor) [with Functor = boost::_bi::bind_t<int, int (*)(int), boost::_bi::list1<boost::arg<1> > >, R = int, T0 = int]’
/boost/include/boost/function/function_template.hpp:716:   instantiated from ‘boost::function1<R, T1>::function1(Functor, typename boost::enable_if_c<(! boost::is_integral::value), int>::type) [with Functor = boost::_bi::bind_t<int, int (*)(int), boost::_bi::list1<boost::arg<1> > >, R = int, T0 = int]’
/boost/include/boost/function/function_template.hpp:1061:   instantiated from ‘boost::function<R(T0)>::function(Functor, typename boost::enable_if_c<(! boost::is_integral::value), int>::type) [with Functor = boost::_bi::bind_t<int, int (*)(int), boost::_bi::list1<boost::arg<1> > >, R = int, T0 = int]’
main.cpp:15:   instantiated from here
/boost/include/boost/bind/bind.hpp:882: error: returning reference to temporary
make: *** [all] Error 1

Answer 1

我用GCC 4.4（CentOS 6）运行你的代码，其中Boost 1.41（捆绑在CentOS中）和Boost 1.64（最新版）。您的代码没有任何问题。

也许你把事情和事情搞混了？

boost::function<int(int)> bfoo = boost::bind(foo, boost::placeholders::_1); // #1 works
boost::function<int(int)> bfoo = boost::bind(foo, _1); // #2 _1 is from boost -> works
std::function<int(int)> bfoo = std::bind(foo, std::placeholders::_1); // #3 works

std::function<int(int)> bfoo = std::bind(foo, _1); // #4 not work
boost::function<int(int)> bfoo = boost::bind(foo, std::placeholders::_1); #5 not work

-std = c ++ 0x导致使用boost 1.64返回临时引用

1 个答案: