struct 和 (对象)std:string不要混用

本文探讨了在C++中使用结构体时,如何正确地初始化std::string成员变量。若未正确初始化可能导致segment fault错误,并提供了解决方案。

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例子

typedef struct
{
   std:string  features;
} Row;

 

Row row;

row.feautres = "hello";

可能出错,因为struct分配的时候,仅仅是分配内存空间,并没有对里面的对象进行必要的初始化,这样就有可能到只row.features.assign(xxx)报错segment fault(概率性的)

 

参考:

  1. http://stackoverflow.com/questions/20452581/segmentation-fault-assigning-stdstring-in-a-struct
  2. http://stackoverflow.com/questions/3411815/how-to-use-a-c-string-in-a-structure-when-malloc-ing-the-same-structure

 

转载于:https://www.cnblogs.com/yuankui/p/3670116.html

49725@DESKTOP-CB4LRLP /cygdrive/f/S $ g++ -mwindows screensaver_clock.cpp -o screensaver_ -lcomctl32 -lgdi32 -luser32 screensaver_clock.cpp: In function 'void LoadLearningTime()': screensaver_clock.cpp:36:32: error: no matching function for call to 'std::basic_ifstream<char>::basic_ifstream(const wchar_t*&)' std::ifstream file(LOG_FILE); ^ In file included from screensaver_clock.cpp:5: D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:554:7: note: candidate: 'std::basic_ifstream<_CharT, _Traits>::basic_ifstream(std::basic_ifstream<_CharT, _Traits>&&) [with _CharT = char; _Traits = std::char_traits<char>]' basic_ifstream(basic_ifstream&& __rhs) ^~~~~~~~~~~~~~ D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:554:7: note: no known conversion for argument 1 from 'const wchar_t*' to 'std::basic_ifstream<char>&&' D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:529:7: note: candidate: 'std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const string&, std::ios_base::openmode) [with _CharT = char; _Traits = std::char_traits<char>; std::__cxx11::string = std::__cxx11::basic_string<char>; std::ios_base::openmode = std::_Ios_Openmode]' basic_ifstream(const std::string& __s, ^~~~~~~~~~~~~~ D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:529:7: note: no known conversion for argument 1 from 'const wchar_t*' to 'const string&' {aka 'const std::__cxx11::basic_string<char>&'} D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:513:7: note: candidate: 'std::basic_ifstream<_CharT, _Traits>::basic_ifstream(const char*, std::ios_base::openmode) [with _CharT = char; _Traits = std::char_traits<char>; std::ios_base::openmode = std::_Ios_Openmode]' basic_ifstream(const char* __s, ios_base::openmode __mode = ios_base::in) ^~~~~~~~~~~~~~ D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:513:7: note: no known conversion for argument 1 from 'const wchar_t*' to 'const char*' D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:502:7: note: candidate: 'std::basic_ifstream<_CharT, _Traits>::basic_ifstream() [with _CharT = char; _Traits = std::char_traits<char>]' basic_ifstream() : __istream_type(), _M_filebuf() ^~~~~~~~~~~~~~ D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:502:7: note: candidate expects 0 arguments, 1 provided screensaver_clock.cpp: In function 'void SaveLearningTime()': screensaver_clock.cpp:53:32: error: no matching function for call to 'std::basic_ofstream<char>::basic_ofstream(const wchar_t*&)' std::ofstream file(LOG_FILE); ^ In file included from screensaver_clock.cpp:5: D:/wingcc/mingw64/lib/gcc/x86_64-w64-mingw32/8.1.0/include/c++/fstream:780:7: note: candidate: 'std::basic_ofstream<_CharT, _Traits>::basic_ofstream(std::basic_ofstream<_CharT, _Traits>&&) [with _CharT = char; _Traits = std::char_traits<char>]' basic_ofstream(basic_ofstream&& _优化代码,全代码输出
05-13
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