0

可能重复：
Clang、std::shared_ptr 和 std::less/operator<

所以，是的，标题几乎是整个问题。正如您从下面的代码片段中看到的那样，我确实实现了operator<，所以我不知道发生了什么。

这是代码：

namespace {

struct Transition {
    string name;
    StatePtr toState;

    Transition(string s = string(), StatePtr state = nullptr)
      : name(move(s))
      , toState(move(state))
    {}

    friend bool operator==(Transition const& lhs, Transition const & rhs) {
      return lhs.name == rhs.name && lhs.toState == rhs.toState;
    }

    friend bool operator<(Transition const & lhs, Transition const & rhs);
  };

  struct State {
    string name;
    set<TransitionPtr> transitions;

    explicit State(string s = string())
      : name(move(s))
    {}

    void addTransition(string s, StatePtr sp = nullptr){
      TransitionPtr new_t = make_transition(s, sp);
      for(auto& t : transitions){
        if(t == new_t){
          return;
        }
      }

      transitions.insert(move(new_t)); // This is where the error happens.
    }

  };
}

bool operator<(StateMachine::Transition const & lhs, StateMachine::Transition const & rhs) {
 return lhs.toState.get() < rhs.toState.get();
}

错误信息是：

在 ../llvm_opt_pass/cgd.cpp:3 中包含的文件中：在 /srv/scratch/sigubufo/clang/stable/3.1_src/llvm/include/llvm/Instructions.h:23 中包含的文件中：在/中包含的文件中srv/scratch/sigubufo/clang/stable/3.1_src/llvm/include/llvm/ADT/ArrayRef.h:13：在/srv/scratch/sigubufo/clang/stable/3.1_src/llvm/include/llvm中包含的文件中/ADT/SmallVector.h:24：在 /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/memory:85 中包含的文件中： /usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/unique_ptr.h:486:14：错误：没有匹配的调用函数到 'std::less<_CT>' 类型的对象返回 std::less<_CT>()(__x.get(), __y.get()); ^~~~~~~~~~~~~~~~

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_function.h:237:20：注意：在函数模板的实例化中要求专门化 'std::operator<<::StateMachine::Transition, std::default_delete<::StateMachine::Transition>, ::StateMachine::Transition, std::default_delete<::StateMachine::Transition>>这里 { 返回 __x < __y; } ^

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_tree.h:1285:13：注意：在成员函数的实例化中'std::less::StateMachine::Transition, std::default_delete<::StateMachine::Transition> > >::operator()' 在这里请求 __comp = _M_impl._M_key_compare(_KeyOfValue()(__v), _S_key(__x )); ^

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_set.h:424:9：注意：>在函数的实例化中模板特化 'std::_Rb_tree::StateMachine::Transition, std::default_delete<::StateMachine::Transition>>, std::unique_ptr<::StateMachine::Transition, std::default_delete<::StateMachine::过渡> >，std::_Identity::StateMachine::Transition，std::default_delete<::StateMachine::Transition> > >，std::less::StateMachine::Transition，std::default_delete<::StateMachine: :Transition> > >, std::allocator::StateMachine::Transition, std::default_delete<::StateMachine::Transition> > ::_M_insert_unique::StateMachine::Transition, std::default_delete<::StateMachine: :Transition> > >' 在这里请求 _M_t._M_insert_unique(std::move(__x));^

../llvm_opt_pass/cgd.cpp:72:17：注意：在成员函数 'std::set::StateMachine::Transition、std::default_delete<::StateMachine::Transition>>、std::less 的实例化中::StateMachine::Transition, std::default_delete<::StateMachine::Transition> > >, std::allocator::StateMachine::Transition, std::default_delete<::StateMachine::Transition> >> >::在此处请求插入'transitions.insert(move(new_t)); ^

/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../../include/c++/4.7/bits/stl_function.h:236:7：注意：候选函数不可行：对于第一个参数，没有从 'pointer' (aka '::StateMachine::Transition *') 到 '::StateMachine::Transition *&&&' > 的已知转换；运算符（）（常量_Tp& __x，常量_Tp& __y）常量

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2 回答 2

1

好的，所以解决方案与这个问题相同：Clang, std::shared_ptr 和 std::less/operator<。

基本上这是来自 libstdc++ 的 type_traits 中的一个错误。

于 2012-12-19T13:17:44.200 回答
0

尝试提供自定义函子作为 std::less 的替代方案。

struct cmp  {
    bool operator() ( const Transition& lhs, const Transition& rhs )  {
        return lhs.toState.get() < rhs.toState.get();
     }
 };

std::set< Transition, cmp > transitions;
于 2012-12-19T21:05:44.817 回答