消除-Weffc++提示的告警

最新推荐文章于 2024-07-09 09:31:18 发布

原创最新推荐文章于 2024-07-09 09:31:18 发布 · 1.2k 阅读

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#basic #iterator #instantiation #string #class #编译器

本文介绍使用Cygwin GCC 3.4.4编译过程中遇到的关于__normal_iterator类的警告信息，并提供了解决方案，即通过重定义复制构造函数和赋值运算符来避免这些警告。

使用cygwin GCC3.4.4编译以下代码，编译开关-Wall -Wextra -Weffc++：
const std::string lower(const std::string& src) { std:: string result(src); (void)transform(src.begin(), src.end(), result.begin(), tolower); return result; }
编译器给出以下告警：
$ g++ -c -Wall -Weffc++ stringutil.cpp
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h: In instantiat
ion of `__gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::c
har_traits<char>, std::allocator<char> > >':
stringutil.cpp:11: instantiated from here
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
`class __gnu_cxx::__normal_iterator<const char*, std::basic_string<char, std::ch
ar_traits<char>, std::allocator<char> > >' has pointer data members
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
but does not override `__gnu_cxx::__normal_iterator<const char*, std::basic_st
ring<char, std::char_traits<char>, std::allocator<char> > >(const __gnu_cxx::__n
ormal_iterator<const char*, std::basic_string<char, std::char_traits<char>, std:
:allocator<char> > >&)'
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
or `operator=(const __gnu_cxx::__normal_iterator<const char*, std::basic_strin
g<char, std::char_traits<char>, std::allocator<char> > >&)'
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h: In instantiat
ion of `__gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_tr
aits<char>, std::allocator<char> > >':
stringutil.cpp:11: instantiated from here
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
`class __gnu_cxx::__normal_iterator<char*, std::basic_string<char, std::char_tra
its<char>, std::allocator<char> > >' has pointer data members
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
but does not override `__gnu_cxx::__normal_iterator<char*, std::basic_string<c
har, std::char_traits<char>, std::allocator<char> > >(const __gnu_cxx::__normal_
iterator<char*, std::basic_string<char, std::char_traits<char>, std::allocator<c
har> > >&)'
/usr/lib/gcc/i686-pc-cygwin/3.4.4/include/c++/bits/stl_iterator.h:587: warning:
or `operator=(const __gnu_cxx::__normal_iterator<char*, std::basic_string<char
, std::char_traits<char>, std::allocator<char> > >&)'

仔细阅读，发现stl_iterator.h文件中的__normal_iterator类定义的有瑕疵，不满足Effective C++规范。
因为有个指针类型的成员_M_current，但是却没有重新定义copy函数和赋值函数。为该类增加了以下代码，
告警消除：
__normal_iterator& operator=(const __normal_iterator& right) / { / if (this == &right) / { / return *this; / } / _M_current = right._M_current;/ return *this;/ } __normal_iterator(const __normal_iterator& right): _M_current(/ right._M_current) {}