带有 clang++ v4 和 gcc 6.3 库的自定义分配器

Custom allocators with clang++ v4 and gcc 6.3 libraries

本文关键字：自定义 分配器 clang++ v4 gcc 带有      更新时间：2023-10-16

在库附带 gcc 6.3.1 的系统(arch linux(上使用带有 clang++ 4.0.0 的自定义分配器时，我遇到了很多麻烦。 这是一个最小的非工作示例：

#include <string>
struct myalloc : std::allocator<char> {
  using std::allocator<char>::allocator;
};
struct mystring 
  : std::basic_string<char, std::char_traits<char>, myalloc> {
  using std::basic_string<char, std::char_traits<char>, myalloc>::basic_string;
};
int
main()
{
  mystring r = "hello";
  mystring s (std::move(r));
}

我在这里的目的显然是让myalloc成为一个行为与系统std::allocator完全相同的自定义分配器，并且mystring与std::string相同，只是它使用myalloc。 这应该是最不可能导致问题的情况。 (显然，一旦这起作用，我想进一步自定义分配器。

代码使用 g++ -std=c++14 -Wall -Werror 进行干净编译，但clang++ -std=c++14失败并显示：

In file included from strerror.cc:1:
In file included from /usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/string:52:
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/bits/basic_string.h:477:9: error: 
      no matching constructor for initialization of
      'std::__cxx11::basic_string<char, std::char_traits<char>,
      myalloc>::_Alloc_hider'
      : _M_dataplus(_M_local_data(), std::move(__str._M_get_allocator()))
        ^           ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
strerror.cc:7:8: note: in instantiation of member function
      'std::__cxx11::basic_string<char, std::char_traits<char>,
      myalloc>::basic_string' requested here
struct mystring 
       ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/bits/basic_string.h:109:2: note: 
      candidate constructor not viable: no known conversion from 'typename
      std::remove_reference<allocator<char> &>::type' (aka
      'std::allocator<char>') to 'const myalloc' for 2nd argument
        _Alloc_hider(pointer __dat, const _Alloc& __a = _Alloc())
        ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/bits/basic_string.h:107:14: note: 
      candidate constructor (the implicit move constructor) not viable: requires
      1 argument, but 2 were provided
      struct _Alloc_hider : allocator_type // TODO check __is_final
             ^
/usr/bin/../lib64/gcc/x86_64-pc-linux-gnu/6.3.1/../../../../include/c++/6.3.1/bits/basic_string.h:107:14: note: 
      candidate constructor (the implicit copy constructor) not viable: requires
      1 argument, but 2 were provided
1 error generated.

这只是 clang 或 gcc 库中的错误，还是我的代码在概念上存在问题？

最小

示例的最小修复是将此成员添加到struct myalloc 

template<class> struct rebind {
    using other = myalloc;
};
当然，最好不要从

std：：allocator 继承(在这种情况下，你不需要重新绑定(，也不要从字符串继承，这些类不打算作为公共基础。

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