GCC-4.7编译错误

Question

当我将这段代码的最后一行添加到我的程序代码中时：

typedef std::set<Job> JobSet;
typedef boost::shared_ptr<JobSet> JobSetPtr;
JobSetPtr jobs_;

jobs_->insert ( job );  // line 60

我得到了这个错误：

    g++-4.7  -o /home/kron/Software/Synchronizer/1.0/Main.o -c src/Main.cpp
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h: In instantiation of ‘bool std::less<_Tp>::operator()(const _Tp&, const _Tp&) const [with _Tp = Job]’:
/usr/include/c++/4.7/bits/stl_tree.h:1285:4:   required from ‘std::pair<std::_Rb_tree_iterator<_Val>, bool> std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_insert_unique(const _Val&) [with _Key = Job; _Val = Job; _KeyOfValue = std::_Identity<Job>; _Compare = std::less<Job>; _Alloc = std::allocator<Job>]’
/usr/include/c++/4.7/bits/stl_set.h:415:29:   required from ‘std::pair<typename std::_Rb_tree<_Key, _Key, std::_Identity<_Key>, _Compare, typename _Alloc::rebind<_Key>::other>::const_iterator, bool> std::set<_Key, _Compare, _Alloc>::insert(const value_type&) [with _Key = Job; _Compare = std::less<Job>; _Alloc = std::allocator<Job>; typename std::_Rb_tree<_Key, _Key, std::_Identity<_Key>, _Compare, typename _Alloc::rebind<_Key>::other>::const_iterator = std::_Rb_tree_const_iterator<Job>; std::set<_Key, _Compare, _Alloc>::value_type = Job]’
src/Configuration.hpp:60:27:   required from here
/usr/include/c++/4.7/bits/stl_function.h:236:22: error: no match for ‘operator<’ in ‘__x < __y’
/usr/include/c++/4.7/bits/stl_function.h:236:22: note: candidates are:
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:65:0,
                 from /usr/include/c++/4.7/bits/char_traits.h:41,
                 from /usr/include/c++/4.7/ios:41,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_pair.h:218:5: note: template<class _T1, class _T2> bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
/usr/include/c++/4.7/bits/stl_pair.h:218:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::pair<_T1, _T2>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/char_traits.h:41,
                 from /usr/include/c++/4.7/ios:41,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:299:5: note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
/usr/include/c++/4.7/bits/stl_iterator.h:299:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::reverse_iterator<_Iterator>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/char_traits.h:41,
                 from /usr/include/c++/4.7/ios:41,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:349:5: note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::reverse_iterator<_IteratorL>&, const std::reverse_iterator<_IteratorR>&)
/usr/include/c++/4.7/bits/stl_iterator.h:349:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::reverse_iterator<_IteratorL>’
In file included from /usr/include/c++/4.7/string:54:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/basic_string.h:2566:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.7/bits/basic_string.h:2566:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::basic_string<_CharT, _Traits, _Alloc>’
In file included from /usr/include/c++/4.7/string:54:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/basic_string.h:2578:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
/usr/include/c++/4.7/bits/basic_string.h:2578:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::basic_string<_CharT, _Traits, _Alloc>’
In file included from /usr/include/c++/4.7/string:54:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/basic_string.h:2590:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.7/bits/basic_string.h:2590:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   mismatched types ‘const _CharT*’ and ‘Job’
In file included from /usr/include/c++/4.7/vector:65:0,
                 from src/Main.cpp:2:
/usr/include/c++/4.7/bits/stl_vector.h:1372:5: note: template<class _Tp, class _Alloc> bool std::operator<(const std::vector<_Tp, _Alloc>&, const std::vector<_Tp, _Alloc>&)
/usr/include/c++/4.7/bits/stl_vector.h:1372:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::vector<_Tp, _Alloc>’
In file included from /usr/include/c++/4.7/set:60:0,
                 from src/Configuration.hpp:4,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_tree.h:873:5: note: template<class _Key, class _Val, class _KeyOfValue, class _Compare, class _Alloc> bool std::operator<(const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&, const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_tree.h:873:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/set:61:0,
                 from src/Configuration.hpp:4,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_set.h:721:5: note: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::set<_Key, _Compare, _Alloc>&, const std::set<_Key, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_set.h:721:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::set<_Key, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/set:62:0,
                 from src/Configuration.hpp:4,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_multiset.h:702:5: note: template<class _Key, class _Compare, class _Alloc> bool std::operator<(const std::multiset<_Key, _Compare, _Alloc>&, const std::multiset<_Key, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_multiset.h:702:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::multiset<_Key, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/list:64:0,
                 from /usr/include/boost/algorithm/string/std/list_traits.hpp:15,
                 from /usr/include/boost/algorithm/string/std_containers_traits.hpp:20,
                 from /usr/include/boost/algorithm/string.hpp:18,
                 from src/Configuration.hpp:9,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_list.h:1659:5: note: template<class _Tp, class _Alloc> bool std::operator<(const std::list<_Tp, _Alloc>&, const std::list<_Tp, _Alloc>&)
/usr/include/c++/4.7/bits/stl_list.h:1659:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::list<_Tp, _Alloc>’
In file included from /usr/include/c++/4.7/deque:65:0,
                 from /usr/include/boost/algorithm/string/find_format.hpp:14,
                 from /usr/include/boost/algorithm/string/replace.hpp:22,
                 from /usr/include/boost/algorithm/string.hpp:25,
                 from src/Configuration.hpp:9,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_deque.h:274:5: note: template<class _Tp, class _Ref, class _Ptr> bool std::operator<(const std::_Deque_iterator<_Tp, _Ref, _Ptr>&, const std::_Deque_iterator<_Tp, _Ref, _Ptr>&)
/usr/include/c++/4.7/bits/stl_deque.h:274:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::_Deque_iterator<_Tp, _Ref, _Ptr>’
In file included from /usr/include/c++/4.7/deque:65:0,
                 from /usr/include/boost/algorithm/string/find_format.hpp:14,
                 from /usr/include/boost/algorithm/string/replace.hpp:22,
                 from /usr/include/boost/algorithm/string.hpp:25,
                 from src/Configuration.hpp:9,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_deque.h:282:5: note: template<class _Tp, class _RefL, class _PtrL, class _RefR, class _PtrR> bool std::operator<(const std::_Deque_iterator<_Tp, _RefL, _PtrL>&, const std::_Deque_iterator<_Tp, _RefR, _PtrR>&)
/usr/include/c++/4.7/bits/stl_deque.h:282:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::_Deque_iterator<_Tp, _RefL, _PtrL>’
In file included from /usr/include/c++/4.7/deque:65:0,
                 from /usr/include/boost/algorithm/string/find_format.hpp:14,
                 from /usr/include/boost/algorithm/string/replace.hpp:22,
                 from /usr/include/boost/algorithm/string.hpp:25,
                 from src/Configuration.hpp:9,
                 from src/Main.cpp:5:
/usr/include/c++/4.7/bits/stl_deque.h:1947:5: note: template<class _Tp, class _Alloc> bool std::operator<(const std::deque<_Tp, _Alloc>&, const std::deque<_Tp, _Alloc>&)
/usr/include/c++/4.7/bits/stl_deque.h:1947:5: note:   template argument deduction/substitution failed:
In file included from /usr/include/c++/4.7/string:50:0,
                 from /usr/include/c++/4.7/bits/locale_classes.h:42,
                 from /usr/include/c++/4.7/bits/ios_base.h:43,
                 from /usr/include/c++/4.7/ios:43,
                 from /usr/include/c++/4.7/ostream:40,
                 from /usr/include/c++/4.7/iostream:40,
                 from src/Main.cpp:1:
/usr/include/c++/4.7/bits/stl_function.h:236:22: note:   ‘const Job’ is not derived from ‘const std::deque<_Tp, _Alloc>’
make: *** [/home/kron/Software/Synchronizer/1.0/Main.o] Error 1

是我的错吗？如果是，我做错了什么？如果不是，是否有人也有同样的错误？

Answer 1

您似乎没有提供用于比较Job类型的两个对象的<运算符的定义。

当您将对象插入到std::set中时，容器需要知道它应该插入项的位置，容器需要将要插入的对象与集合中已经存在的项进行比较。为了做到这一点，它使用了<运算符，我猜你还没有提供。std::set<Job>根本不知道如何比较两个Job类型的对象。

因此您可以为Job类提供operator<。

或者，定义此函数器来比较Job对象：

struct JobComparer
{
    bool operator()(Job const &j1, Job const &j2)
    {
        //compare j1 and j2 and return true or false
    }
};

然后使用它作为：

typedef std::set<Job, JobComparer> JobSet;

或者，您可以将std::less指定为explained here。

你可以看到这个主题：

• std::set with user defined type, how to ensure no duplicates

Answer 2

Nawaz提供了一个简单的答案，但我认为它值得一个更完整的答案。

在C++中，对象的set是一个没有重复的有序容器。为了能够对对象进行排序，它使用了不同于对象本身的第二个模板参数:一个用于比较两个对象的functor。它还使用第三个参数进行内存分配，在这里没有用。

使用set时，需要提供两个参数：

struct NameComparator {
    template <typename T>
    bool operator()(T const& left, T const& right) {
        return left.name() < right.name();
    }
};

std::set<Job, NameComparator> JobSet;

提供的比较器应该定义一些顺序的概念。基本上，考虑一下<对两个整数是如何工作的：

• it是非自反的：x < x从不保持
• ，它是反对称的:如果x < y，则y < x为
• ，它是传递的:如果<代码>D13和<代码>D14，则x < z

因为这是一种常见的关系，所以这样的函数库存在于标准库中：template <typename T> struct std::less;，它适用于任何类型的T，对于给定的两个实例，您可以使用运算符<。

实际上，您没有明确指出的set的第二个参数缺省为std::less<TypeOfObjectInSet>。这意味着当为其提供定义了<的对象时，它可以开箱即用。

因此，您有3个解决方案。

如果您的对象接受一种“自然”顺序关系，那么您可以定义operator<或专门化std::less。否则，如果你只需要这个集合的一些顺序关系，那么你可以提供你自己的比较器。

请注意，如果不需要订单，则可以使用unordered_set。它需要散列和平等关系。