std

问题 According to some older StackOverflow questions ( Unable to pass std::wstring across DLL , C++ DLL returning pointer to std::list<std::wstring> ) it's not considered safe for a C++ DLL to return a std::wstring because there's no guarantee the main program has the same definition of std::wstring and therefore it might cause a crash. However, in http://en.cppreference.com/w/cpp/string/basic_string , it seems std::wstring can be used interchangeably with a WCHAR array now: (Since C++11) The

问题 For the code I am currently working on, we sometimes need to compile on some older systems with older compilers (e.g.- we run sims on an older IBM BlueGene/L, who's support contract dictates some quite old C++ compiler). The code itself makes use of shared_ptrs, and was originally written to use std::tr1::shared_ptr. When compiling on the old BlueGene machine, I quickly realized that it doesn't have a tr1:: implementation, and so I switched to boost::shared_ptr. Turns out there is also a

问题 My current understanding of the difference between std::string and std::wstring is simply the buffer's type; namely, char vs wchar_t , respectively. I've also read that most (if not all) linux distros use char for any and all strings, both ASCII as well as UTF, where Windows is the primary OS that uses wchar_t anymore. However, there are a few more string types that I want to get straight in my head: u16string and u32string , which are strings with 2-byte and 4-byte buffers, respectively. So,

问题 After a long day of coding i accidentaly wrote cout << "some text" << cout; instead of cout << "some text" << endl; Now it printed out a memory address. What does it point to ? 回答1: std::cout is an instance of std::ostream , and, before C++11, that had a conversion operator to void*. It seems your code is triggering that conversion, giving you the address of the std::cout object. 来源： https://stackoverflow.com/questions/28872624/cout-cout-what-does-the-output-stand-for

问题 After a long day of coding i accidentaly wrote cout << "some text" << cout; instead of cout << "some text" << endl; Now it printed out a memory address. What does it point to ? 回答1: std::cout is an instance of std::ostream , and, before C++11, that had a conversion operator to void*. It seems your code is triggering that conversion, giving you the address of the std::cout object. 来源： https://stackoverflow.com/questions/28872624/cout-cout-what-does-the-output-stand-for

问题 I understand that the rand() function generates pseudo-random numbers based on the seed it is given, and that on a given platform it will always generate the same sequence of numbers from the same seed, what I want to know is why it gives a different sequence across platforms that use the same library? I.e. how is rand() implemented? 回答1: The C++ standard does not specify what algorithm is used for the rand() function. The functionality is defined by whoever wrote the standard library on your

问题 is this code ok? void SomeClass :: foo(const char * _name) { //name is of type const char * name = std::string(_name).c_str(); } it looks like it is working, but iam not sure if it is ok should i do an old school strcpy ? 回答1: It's ok since it compiles and doesn't cause undefined behavior. It's not ok since name points to an invalid memory after the statement completes execution. name = std::string(_name).c_str(); At the end of this statement the temporary std::string is destroyed and it

问题 I am taking a programming class in school and I wanted to start doing some c++ programming out of class. My school using Microsoft Visual C++ 6.0 (which is from 1998) so it still uses <iostream.h> rather than <iostream> and using namespace std . When I started working, I couldn't figure out how and when to use using namespace std and when to just use things like std::cout<<"Hello World!"<<'\n'; (for example) as well as it's limits and other uses for the namespace keyword. In particular, if I

问题 I am taking a programming class in school and I wanted to start doing some c++ programming out of class. My school using Microsoft Visual C++ 6.0 (which is from 1998) so it still uses <iostream.h> rather than <iostream> and using namespace std . When I started working, I couldn't figure out how and when to use using namespace std and when to just use things like std::cout<<"Hello World!"<<'\n'; (for example) as well as it's limits and other uses for the namespace keyword. In particular, if I

问题 I found myself in a situation where I would have liked to have an analog of unique_ptr 's release() for std::vector<> . E.g.: std::vector<int> v(SOME_SIZE); //.. performing operations on v int* data = v.release(); // v.size() is now 0 and the ownership of the internal array is released functionUsingAndInternallyDeletingRowPointer(data); Is there a particular reason why this kind of possibility is not provided? May that impose some constraint on std::vector 's the internal implementation? Or