char_traits类的两个成员函数

本文详细解析了Copy_s和Move_s两个函数的工作原理及其区别。Copy_s用于复制元素,而Move_s则在此基础上增加了对相同字符串的特殊处理机制,以避免在移动过程中发生数据覆盖。

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	static _Elem *__CLRCALL_OR_CDECL _Copy_s(_Elem *_First1, size_t _Dest_size,
		const _Elem *_First2, size_t _Count)
		{	// copy [_First1, _First1 + _Count) to [_First2, ...)
//		_DEBUG_POINTER(_First1);
//		_DEBUG_POINTER(_First2);
		_SCL_SECURE_CRT_VALIDATE(_Dest_size >= _Count, NULL);
		_Elem *_Next = _First1;
		for (; 0 < _Count; --_Count, ++_Next, ++_First2)
			assign(*_Next, *_First2);
		return (_First1);
		}

	static _Elem *__CLRCALL_OR_CDECL _Move_s(_Elem *_First1, size_t _Dest_size,
		const _Elem *_First2, size_t _Count)
		{	// move [_First1, _First1 + _Count) to [_First2, ...)
//		_DEBUG_POINTER(_First1);
//		_DEBUG_POINTER(_First2);
		_SCL_SECURE_CRT_VALIDATE(_Dest_size >= _Count, NULL);
		_Elem *_Next = _First1;
		if (_First2 < _Next && _Next < _First2 + _Count)//相同的字符串
			for (_Next += _Count, _First2 += _Count; 0 < _Count; --_Count)
				assign(*--_Next, *--_First2);
		else
			for (; 0 < _Count; --_Count, ++_Next, ++_First2)
				assign(*_Next, *_First2);
		return (_First1);
		}
_Copy_s和_Move_s两个函数非常相似,不同是_Move_s多相同字符串的判断。如果是相同的字符串,则从字符窜尾倒序复制。顺序复制的话,会造成覆盖问题。

(gdb) bt #0 0x005cd5ff in std::_Rb_tree_decrement(std::_Rb_tree_node_base*) () from /usr/lib/libstdc++.so.6 #1 0x080e3b15 in std::_Rb_tree_iterator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> >::operator-- (this=0xbfbacdc4) at /usr/lib/gcc/i686-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_tree.h:199 #2 0x080e3873 in std::_Rb_tree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement>, std::_Select1st<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> > >::_M_insert_unique (this=0x89b53a0, __v=...) at /usr/lib/gcc/i686-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_tree.h:1179 #3 0x080e31df in std::_Rb_tree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement>, std::_Select1st<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> > >::_M_insert_unique_ (this=0x89b53a0, __position=..., __v=...) at /usr/lib/gcc/i686-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_tree.h:1217 #4 0x080e2ee7 in std::map<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, STDTM::AlarmElement, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, STDTM::AlarmElement> > >::insert (this=0x89b53a0, __position=..., __x=...) at /usr/lib/gcc/i686-redhat-linux/4.4.7/../../../../include/c++/4.4.7/bits/stl_map.h:540
06-13
||=== Build file: "no target" in "no project" (compiler: unknown) ===| E:\C++\2\main.cpp||In function 'int main()':| E:\C++\2\main.cpp|11|error: no match for 'operator>>' (operand types are 'std::basic_istream<char>::__istream_type' {aka 'std::basic_istream<char>'} and '<unresolved overloaded function type>')| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|120|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__istream_type& (*)(std::basic_istream<_CharT, _Traits>::__istream_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|120|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_istream<char>::__istream_type& (*)(std::basic_istream<char>::__istream_type&)' {aka 'std::basic_istream<char>& (*)(std::basic_istream<char>&)'}| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|124|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__ios_type& (*)(std::basic_istream<_CharT, _Traits>::__ios_type&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>; std::basic_istream<_CharT, _Traits>::__ios_type = std::basic_ios<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|124|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_istream<char>::__ios_type& (*)(std::basic_istream<char>::__ios_type&)' {aka 'std::basic_ios<char>& (*)(std::basic_ios<char>&)'}| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|131|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(std::ios_base& (*)(std::ios_base&)) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|131|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::ios_base& (*)(std::ios_base&)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|168|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(bool&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|168|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'bool&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|172|note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(short int&) [with _CharT = char; _Traits = std::char_traits<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|172|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'short int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|175|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(short unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|175|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'short unsigned int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|179|note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(int&) [with _CharT = char; _Traits = std::char_traits<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|179|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|182|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|182|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'unsigned int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|186|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|186|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|190|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|190|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long unsigned int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|195|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|195|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long long int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|199|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long long unsigned int&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|199|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long long unsigned int&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|214|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(float&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|214|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'float&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|218|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|218|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'double&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|222|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(long double&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|222|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'long double&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|235|note: candidate: 'std::basic_istream<_CharT, _Traits>::__istream_type& std::basic_istream<_CharT, _Traits>::operator>>(void*&) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__istream_type = std::basic_istream<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|235|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'void*&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|259|note: candidate: 'std::basic_istream<_CharT, _Traits>& std::basic_istream<_CharT, _Traits>::operator>>(std::basic_istream<_CharT, _Traits>::__streambuf_type*) [with _CharT = char; _Traits = std::char_traits<char>; std::basic_istream<_CharT, _Traits>::__streambuf_type = std::basic_streambuf<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|259|note: no known conversion for argument 1 from '<unresolved overloaded function type>' to 'std::basic_istream<char>::__streambuf_type*' {aka 'std::basic_streambuf<char>*'}| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\bits\basic_string.tcc|1465|note: candidate: 'template<class _CharT, class _Traits, class _Alloc> std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, std::__cxx11::basic_string<_CharT, _Traits, _Alloc>&)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\bits\basic_string.tcc|1465|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: couldn't deduce template parameter '_Alloc'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\bits\istream.tcc|931|note: candidate: 'std::basic_istream<_CharT, _Traits>& std::operator>>(std::basic_istream<_CharT, _Traits>&, _CharT&) [with _CharT = char; _Traits = std::char_traits<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\bits\istream.tcc|931|note: no known conversion for argument 2 from '<unresolved overloaded function type>' to 'char&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|756|note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char&)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|756|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: cannot convert 'std::endl' (type '<unresolved overloaded function type>') to type 'unsigned char&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|761|note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char&)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|761|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: cannot convert 'std::endl' (type '<unresolved overloaded function type>') to type 'signed char&'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|799|note: candidate: 'std::basic_istream<_CharT2, _Traits2>& std::operator>>(std::basic_istream<_CharT2, _Traits2>&, _CharT2*) [with _CharT2 = char; _Traits2 = std::char_traits<char>; _CharT = char; _Traits = std::char_traits<char>]'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|799|note: no known conversion for argument 2 from '<unresolved overloaded function type>' to 'char*'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|803|note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, unsigned char*)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|803|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: cannot convert 'std::endl' (type '<unresolved overloaded function type>') to type 'unsigned char*'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|808|note: candidate: 'template<class _Traits> std::basic_istream<char, _Traits>& std::operator>>(std::basic_istream<char, _Traits>&, signed char*)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|808|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: cannot convert 'std::endl' (type '<unresolved overloaded function type>') to type 'signed char*'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|980|note: candidate: 'template<class _Istream, class _Tp> typename std::enable_if<std::__and_<std::__not_<std::is_lvalue_reference<_Tp> >, std::__is_convertible_to_basic_istream<_Istream>, std::__is_extractable<typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type, _Tp&&, void> >::value, typename std::__is_convertible_to_basic_istream<_Tp>::__istream_type>::type std::operator>>(_Istream&&, _Tp&&)'| E:\CodeBlocks\MinGW\lib\gcc\x86_64-w64-mingw32\8.1.0\include\c++\istream|980|note: template argument deduction/substitution failed:| E:\C++\2\main.cpp|11|note: couldn't deduce template parameter '_Tp'| E:\C++\2\main.cpp|12|error: 'class cube' has no member named 'setchang'| E:\C++\2\main.cpp|13|error: 'class cube' has no member named 'getchang'| ||=== Build failed: 3 error(s), 0 warning(s) (0 minute(s), 0 second(s)) ===| 是什么意思,怎么解决
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07-17
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