All geek questions in one place

Why below code is not compiled with gcc but compiled with clang

The code below is compiled using clang but not gcc, any explanation is a bug in gcc?

Its just a class that contains the unique_ptr vector and std :: function as a member, and when I create the vector of this class, I cannot say that this is a reserve or resize. push_back works fine with std :: move, whereas this only happens with gcc and not clang.

#include <algorithm>                                                                                                                                               
#include <memory>                                                                                                                                                          
#include <utility>                                                                                                                                                         
#include <iostream>  
#include <vector>
#include <functional>

using namespace std;                                                                                                                                                       

class ABC                                                                                                                                                                  
{                                                                                                                                                                          
public:                                                                                                                                                                    
    ABC()                                                                                                                                                                  
          {}                                                                                                                                                               
  private:                                                                                                                                                                 
    std::vector<std::unique_ptr<int>> up;                                                                                                                                  
    std::function<void (int*)> func;                                                                                                                                       
};                                                                                                                                                                         

int main()                                                                                                                                                                 
{                                                                                                                                                                          
    ABC a;                                                                                                                                                                 
    std::vector<ABC> vec;                                                                                                                                                  
    vec.reserve(1);                                                                                                                                                        
}

The error message looks like below for gcc

In file included from /opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_tempbuf.h:60:0,
                 from /opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_algo.h:62,
                 from /opt/wandbox/gcc-7.1.0/include/c++/7.1.0/algorithm:62,
                 from prog.cc:1:
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_construct.h: In instantiation of 'void std::_Construct(_T1*, _Args&& ...) [with _T1 = std::unique_ptr<int>; _Args = {const std::unique_ptr<int, std::default_delete<int> >&}]':
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:83:18:   required from 'static _ForwardIterator std::__uninitialized_copy<_TrivialValueTypes>::__uninit_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<int>*, std::vector<std::unique_ptr<int> > >; _ForwardIterator = std::unique_ptr<int>*; bool _TrivialValueTypes = false]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:134:15:   required from '_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<int>*, std::vector<std::unique_ptr<int> > >; _ForwardIterator = std::unique_ptr<int>*]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:289:37:   required from '_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = __gnu_cxx::__normal_iterator<const std::unique_ptr<int>*, std::vector<std::unique_ptr<int> > >; _ForwardIterator = std::unique_ptr<int>*; _Tp = std::unique_ptr<int>]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_vector.h:331:31:   required from 'std::vector<_Tp, _Alloc>::vector(const std::vector<_Tp, _Alloc>&) [with _Tp = std::unique_ptr<int>; _Alloc = std::allocator<std::unique_ptr<int> >]'
prog.cc:10:7:   required from 'void std::_Construct(_T1*, _Args&& ...) [with _T1 = ABC; _Args = {const ABC&}]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:83:18:   required from 'static _ForwardIterator std::__uninitialized_copy<_TrivialValueTypes>::__uninit_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = const ABC*; _ForwardIterator = ABC*; bool _TrivialValueTypes = false]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:134:15:   required from '_ForwardIterator std::uninitialized_copy(_InputIterator, _InputIterator, _ForwardIterator) [with _InputIterator = const ABC*; _ForwardIterator = ABC*]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_uninitialized.h:289:37:   required from '_ForwardIterator std::__uninitialized_copy_a(_InputIterator, _InputIterator, _ForwardIterator, std::allocator<_Tp>&) [with _InputIterator = const ABC*; _ForwardIterator = ABC*; _Tp = ABC]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_vector.h:1263:35:   required from 'std::vector<_Tp, _Alloc>::pointer std::vector<_Tp, _Alloc>::_M_allocate_and_copy(std::vector<_Tp, _Alloc>::size_type, _ForwardIterator, _ForwardIterator) [with _ForwardIterator = const ABC*; _Tp = ABC; _Alloc = std::allocator<ABC>; std::vector<_Tp, _Alloc>::pointer = ABC*; std::vector<_Tp, _Alloc>::size_type = long unsigned int]'
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/vector.tcc:73:40:   required from 'void std::vector<_Tp, _Alloc>::reserve(std::vector<_Tp, _Alloc>::size_type) [with _Tp = ABC; _Alloc = std::allocator<ABC>; std::vector<_Tp, _Alloc>::size_type = long unsigned int]'
prog.cc:24:18:   required from here
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/stl_construct.h:75:7: error: use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = int; _Dp = std::default_delete<int>]'
     { ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); }
       ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from /opt/wandbox/gcc-7.1.0/include/c++/7.1.0/memory:80:0,
                 from prog.cc:2:
/opt/wandbox/gcc-7.1.0/include/c++/7.1.0/bits/unique_ptr.h:388:7: note: declared here
       unique_ptr(const unique_ptr&) = delete;
       ^~~~~~~~~~
+4
source share
3 answers

, std::function move ctor noexcept, std::vector ctor, noexcept ( ).

, std::unique_ptr () , ABC . , ABC noexcept -movable , noexcept -movable.

std::function, : .resize() A.up (a std::vector noexcept), std::unique_ptr ( up) , .

coliru: noexcept, vec.reserve(), , .

ABC(ABC&&) = default , ( default ed) move ctor (. ).

A coliru ( ctor noexcept): .

, std::function std::unique_ptr, nothrow move ctor.

+3

, GCC ; -ctor 1. , :

class ABC                                                                                                                                                                  
{                                                                                                                                                                          
public:                                                                                                                                                                    
    ABC() = default;        // <-- 
    ABC(ABC&&) = default;   // <--
  private:                                                                                                                                                                 
    std::vector<std::unique_ptr<int>> up;                                                                                                                                  
    std::function<void (int*)> func;                                                                                                                                       
};

1 ( , ), , copy-ctor ABC noexcept move-ctor ( , ). noexcept move-ctor :

main.cpp:14:4: note: 'ABC::ABC(ABC&&) noexcept' is implicitly deleted because its exception-specification does not match the implicit exception-specification ''
    ABC(ABC&&) noexcept = default;
    ^~~

, no- noexcept move-ctor . - .

, std::function noexcept move-ctor. std::function noexcept move-ctor ( ), copy-ctor. unique_ptr , .

+3

GCC accepted the absence of noexcept in std :: function move ctor as an error

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81017

// - C ++ -

  /** 2227        *  @brief %Function move constructor. 2228        *  @param
 __x A %function object rvalue with identical call signature. 2229        * 2230        
*  The newly-created %function contains the target of @a __x 2231        *  (if 
it has one). 2232        */ 2233       
function(function&& __x) : _Function_base()  {     __x.swap(*this); }
+1
source

Source: https://habr.com/ru/post/1678758/

More articles:


All Articles