Program Crash on C++ regarding checking if data exists

Question

What I do here is convert my input name to char then check from the text file if char a which is the input name exists or equal to existing nameData. nameData is the variable stored in the text file. But my program crashed once it detects that the input is new. What may seemed the problem in this problem? I'm getting the crash from else condition part.

char *nameData;
    char *passData;
    QByteArray nameBa;
    nameBa = name.toLatin1();
    nameData = nameBa.data();
    passData = pass.data();

    char *a;
    QByteArray aBa;
    aBa = name.toLatin1();
    a = aBa.data();

    std::fstream dataProfile;
    dataProfile.open("D:/Data.txt", std::ios::in);

while(!dataProfile.eof())
    {
        dataProfile.getline(nameData, 90, ' ');
        dataProfile.getline(passData, 90);
        if(std::strcmp(nameData, a)==0)
        {
           std::cout << "Profile Already exists\n";
           //if break here, still crash to else condition
        }
        else
        {
            std::cout << "Not Exists\n";
        }
        break;
    }

Possible duplicate of [Why is “while (!feof(file))” always wrong?](https://stackoverflow.com/questions/5431941/why-is-while-feoffile-always-wrong) — mch, Mar 07 '19 at 08:42
Are you sure with the `break;` at the end of the `while`? That makes the `while` to an `if`. — mch, Mar 07 '19 at 08:43

score 3 · Answer 1 · edited Mar 07 '19 at 10:48

3

char *nameData; and char *passData; are not allocated with memory. you need to pre-allocated memory like this : http://www.cplusplus.com/reference/istream/istream/getline/

char name[256], title[256];

std::cout << "Please, enter your name: ";
std::cin.getline (name,256);

std::cout << "Please, enter your favourite movie: ";
std::cin.getline (title,256);

edited Mar 07 '19 at 10:48

Fryz

2,119
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answered Mar 07 '19 at 09:06

alon

220
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It is not assignable as per Qt – Rin_asdfghjkl Mar 08 '19 at 00:59

score 1 · Accepted Answer · answered Mar 08 '19 at 02:00

1

I already figured it out, what I did is:

char nameData[90];
char passData[90];
strcpy(nameData, name.toStdString().c_str()); //name is string
strcpy(passData, pass.data()); //pass is bytearray

answered Mar 08 '19 at 02:00

Rin_asdfghjkl

65
8

Program Crash on C++ regarding checking if data exists

2 Answers2