local string always corrupt

[rohit713]

I am developing application in mac os mavericks using Qt Creator 3.0.0. having QT 4.8.4 my problem is when i trying to copy QString in char array value of string becomes not accessible.

for refernce

#include "mainwindow.h"

#include "ui_mainwindow.h"

#include <QString>

#include <QDebug>


MainWindow::MainWindow(QWidget *parent) :

    QMainWindow(parent),

    ui(new Ui::MainWindow)

{

    ui->setupUi(this);


    abc("risk");

}


MainWindow::~MainWindow()

{

    delete ui;

}



void MainWindow::abc(QString ijl)

{

    char pr[40];

    memset(pr,NULL,40);


    strcpy(pr,ijl.toLocal8Bit().data());


    qDebug()<<ijl.toLocal8Bit().data();


}

[mrjj]

Hi
What is ijl ?
and can you also show the output ?

[jsulm]

@rohit713 said in local string always corrupt:

value of string becomes not accessible.

Value of which string? pr?
Why not

memset(pr, 0, 40);

?

[ambershark]

This works fine for me, so there is something more going on. You'll have to share some more information. What does the debugger say for the address and the data contained in the array?

Also how do you know pr is not accessible? You never output it via qdebug or anything else.

I tried this code (granted I used qt5 since I don't have 4 installed) but it worked fine.

[rohit713]

@mrjj ijl is qstring which is pass as an parameter in function abc ().

[rohit713]

@jsulm value of ijl string which is passed in function abc().

[rohit713]

@ambershark yes its work fine in qt 5 but my problem occur in qt 4 .ijl is coruupetd debugger shows the locale value not accesible while we copy this to pr its crash .

[jsulm]

@rohit713 But what do you mean by "not accessible"? Was it accessible before strcpy?
Note this (from http://doc.qt.io/qt-5/qstring.html#toLocal8Bit):
"The returned byte array is undefined if the string contains characters not supported by the local 8-bit encoding."

[Christian Ehrlicher]

You do not check if ijl.toLocal8Bit() is shorter than 40 bytes.

[rohit713]

@jsulm before strcpy it contain "risk" after calling strcpy it gives not accesible.

[jsulm]

@rohit713 As @Christian-Ehrlicher said: you implemented a nice example for stack overflow :-)
You should use strncpy.

[aha_1980]

@jsulm

Even better: qstrncpy ;)

[rohit713]

@jsulm i also tried strncpy but the same problem occurs .

[jsulm]

@rohit713 Can you show how you used strncpy?

[rohit713]

This post is deleted!

[rohit713]

@jsulm strncpy(pr,ijl.toLocal8Bit().data(),ijl.length());

[jsulm]

@rohit713 This is same stack overflow as before...

[rohit713]

@jsulm can u share the stack overflow link

[jsulm]

@rohit713 What link? Think about what will happen if ijl.toLocal8Bit().data() is longer than pr.

[aha_1980]

@rohit713

Use qstrncpy(pr, ijl.toLocal8Bit().constData(),sizeof(pr));