Thread: Is this good C++ code? And should the tests on swscanf work.

Code:

#include <iostream>
#include <wchar.h>

int main()
{
    bool failed = false;
    int i = 0;
    wchar_t wstr[20];

    std::wstring wide_input(L"42 test");

    std::wstring wide_result(L"test");

    std::cout << "Testing swscanf function!" << std::endl;
    swscanf(wide_input.c_str(), L"%d %s", &i, &wstr);

    if (i != 42){
      failed = true;
    }

    if (wstr != wide_result){
      failed = true;
    }

    if (failed == true){
        return -1;
    }

    std::cerr <<  "Passed all of the tests";
    return 0;
}

I am trying to use cppunit to test the wxWidgets building under Windows 10 32 bit MSys2 (MSys2 is a fork of CygWin).

And, the cppunit tests segfaults; where it segfaults suggest a broken swscanf support function called __mingw_swformat in the crt library.

The MSys2 GCC crt library is based on MinGW-64 crt library with only slight patches.

Edit: The above code crashes when compiled with the MSys2 GCC (Rev1, Built by MSYS2 project) 6.3.0.

Tim S.

You're forgetting that an array is already interpreted as a pointer to the first element, so you shouldn't have the ampersand before wstr.

Also, to read a wide string you need to use "%ls". (That's a lowercase L.)

As for good C++, people usually forgo the scanf function in favour of stringstream.

Code:

#include <iostream>
#include <string>
#include <sstream>
#include <cwchar>

using std::wcout;

int main() {
    int i = 0;
    wchar_t wstr[20] = L"default";
    std::wstring wide_input(L"42 test"); 
    std::wstring wide_result(L"test");

    wcout << L"Testing swscanf function\n";

    swscanf(wide_input.c_str(), L"%d %ls", &i, wstr);
 
    if (i != 42) {
      wcout << L"i != 42\n";
      return 1;
    }
 
    if (wstr != wide_result){
      wcout << L"wstr != wide_result\n";
      return 1;
    }
 
    wcout <<  L"swscanf passed all of the tests\n";

    wcout << L"Testing wstringstream\n";

    i = 0;
    wstr[0] = L'\0';

    std::wstringstream wss(wide_input);
    wss >> i;
    wss >> wstr;

    if (i != 42) {
      wcout << L"i != 42\n";
      return 1;
    }
 
    if (wstr != wide_result){
      wcout << L"wstr != wide_result\n";
      return 1;
    }
 
    wcout <<  L"wstringstream passed all of the tests\n";

    return 0;
}

Thank you algorism.

I can now see if wstringstream passes.

Tim S.