valgrind --tool=memcheck --leak-check=yes ./app

==7090== HEAP SUMMARY:
==7090==     in use at exit: 5,623,365 bytes in 36,268 blocks
==7090==   total heap usage: 32,454,680 allocs, 32,418,412 frees, 12,822,939,874 bytes allocated
................................
==7090== LEAK SUMMARY:
==7090== definitely lost: 20,163 bytes in 74 blocks
==7090== indirectly lost: 60,053 bytes in 1,273 blocks
==7090== possibly lost: 396,167 bytes in 2,169 blocks
==7090== still reachable: 4,834,822 bytes in 31,576 blocks
==7090== suppressed: 0 bytes in 0 blocks
==7090== Reachable blocks (those to which a pointer was found) are not shown.
==7090== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==7090==
==7090== For counts of detected and suppressed errors, rerun with: -v
==7090== Use --track-origins=yes to see where uninitialised values come from
==7090== ERROR SUMMARY: 20905 errors from 1583 contexts (suppressed: 15 from 2)

==3816== HEAP SUMMARY:
==3816==     in use at exit: 7,746,701 bytes in 36,248 blocks
==3816==   total heap usage: 827,800,342 allocs, 827,764,094 frees, 105,404,761,516 bytes allocated
..................................
==3816== LEAK SUMMARY:
==3816== definitely lost: 19,835 bytes in 38 blocks
==3816== indirectly lost: 59,805 bytes in 1,237 blocks
==3816== possibly lost: 396,167 bytes in 2,169 blocks
==3816== still reachable: 6,958,734 bytes in 31,628 blocks
==3816== suppressed: 0 bytes in 0 blocks
==3816== Reachable blocks (those to which a pointer was found) are not shown.
==3816== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==3816==
==3816== For counts of detected and suppressed errors, rerun with: -v
==3816== Use --track-origins=yes to see where uninitialised values come from
==3816== ERROR SUMMARY: 13022 errors from 1574 contexts (suppressed: 10 from 2)

int main()
{
  int *a = new int[100];
}

g++ -g -o ex ex.cpp
valgrind --tool=memcheck --leak-check=yes ./ex

==22042== Memcheck, a memory error detector
==22042== Copyright (C) 2002-2013, and GNU GPL'd, by Julian Seward et al.
==22042== Using Valgrind-3.10.1 and LibVEX; rerun with -h for copyright info
==22042== Command: ./ex
==22042==
==22042==
==22042== HEAP SUMMARY:
==22042==     in use at exit: 73,104 bytes in 2 blocks
==22042==   total heap usage: 2 allocs, 0 frees, 73,104 bytes allocated
==22042==
==22042== 400 bytes in 1 blocks are definitely lost in loss record 1 of 2
==22042==    at 0x4C2B800: operator new[](unsigned long) (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==22042==    by 0x40061B: main (ex.cpp:3)
==22042==
==22042== LEAK SUMMARY:
==22042==    definitely lost: 400 bytes in 1 blocks
==22042==    indirectly lost: 0 bytes in 0 blocks
==22042==      possibly lost: 0 bytes in 0 blocks
==22042==    still reachable: 72,704 bytes in 1 blocks
==22042==         suppressed: 0 bytes in 0 blocks
==22042== Reachable blocks (those to which a pointer was found) are not shown.
==22042== To see them, rerun with: --leak-check=full --show-leak-kinds=all
==22042==
==22042== For counts of detected and suppressed errors, rerun with: -v
==22042== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)

int usedmem = mallinfo().uordblks;

#include <QLabel>
#include <malloc.h>

class MemoryStatusWidget : public QLabel
{
public:
    MemoryStatusWidget(QWidget *parent = nullptr);

public:
    void timerEvent(QTimerEvent *) override;
};

MemoryStatusWidget::MemoryStatusWidget(QWidget* parent)
    : QLabel(parent)

{
    startTimer(1000);
}

void MemoryStatusWidget::timerEvent(QTimerEvent *)
{
    int usedmem = mallinfo().uordblks;

    setText(tr("Memory Usage:%1 MB").arg(QString::number((double)usedmem / (1024 * 1024), 'f', 3)));
}