QApplication limits malloc

[SongCn]

Hi everyone,

I've got some problems when I want to dynamically allocate a large array with a QApplication. But the allocation is successfull when I allocate with a QCoreApplication or without Qt at all.

With QApplication, the second allocation fails :
@
int main(int argc, char ** argv)
{

double *matriceBrute,*matriceSortie;
int numberFiles = 1000;
int nCol = 320;
int nRow = 240;
QApplication app(argc,argv);
matriceBrute = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
matriceSortie = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
if (matriceBrute == NULL)
    cout << "Matrice Brute failed" << endl;
else
    cout << "Matrice Brute succeed" << endl;
if (matriceSortie == NULL)
    cout << "Matrice Sortie failed" << endl;
else
    cout << "Matrice Sortie succed" << endl;

}
@

With QCoreApplication, the two allocations are successful :
@
int main(int argc, char ** argv)
{

double *matriceBrute,*matriceSortie;
int numberFiles = 1000;
int nCol = 320;
int nRow = 240;
QCoreApplication app(argc,argv);
matriceBrute = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
matriceSortie = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
if (matriceBrute == NULL)
    cout << "Matrice Brute failed" << endl;
else
    cout << "Matrice Brute succeed" << endl;
if (matriceSortie == NULL)
    cout << "Matrice Sortie failed" << endl;
else
    cout << "Matrice Sortie succed" << endl;

}
@

And without Qt at all, it's also working :
@
int main(int argc, char ** argv)
{

double *matriceBrute,*matriceSortie;
int numberFiles = 1000;
int nCol = 320;
int nRow = 240;
matriceBrute = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
matriceSortie = (double*)malloc(nCol*nRow*numberFiles*sizeof(double));
if (matriceBrute == NULL)
    cout << "Matrice Brute failed" << endl;
else
    cout << "Matrice Brute succeed" << endl;
if (matriceSortie == NULL)
    cout << "Matrice Sortie failed" << endl;
else
    cout << "Matrice Sortie succed" << endl;

}
@

Have any idea how I can make it work with QApplication ? By the way, I'm working on Win7 64 bits with Qt Creator mingw 32 bits.

Thanks.

Song Chen

[Jeroentjehome]

Hi, What QApplication does is protect you from some serious malpractice! From the OS you only get a limited amount of stack! You try to allocate a very large amount of stack data which probably doesn't fit in that part of memory.
Using malloc is highly discouraged in C++ and in Qt it's almost forbidden!
Use the 'new' keyword and put all elements in a QList or QMap! Use Qt containers!! They will be stored in HEAP, not stack. In stack only a list of pointers is kept, so a minimum of stack is required.
You're not writing C++, your doing C!

[SongCn]

Well, I tried with new double[] and std::vector and had the same error. But I'm going to look in QList and QMap.

Thanks