Segmentation error while creating Qt QApplication

Question

I have a program where QApplication is created with a new statement. He falls for an unknown reason. I am using RedHat Linux, g ++ 4.8.2, Qt 4.7.2, which was built with the same compiler.

This source contains many looking useless but harmless fragments, such as the func function with four unused arguments. If I try to remove them and simplify the program a little further, the crash cannot be played back anymore, which, of course, does not mean that the problem is solved.

The accident occurs in the strlen function, which is called from the XSetCommand system function. Adding my own simple toolkit allowed me to see strlen getting a damaged pointer, see below.

#include <QApplication>
#include <QMessageBox>

void func(void *, void *, void *, void *)  {}

struct Gui
{
  QApplication qApplication;
  Gui(int argc, char ** argv) : qApplication(argc, argv)  {}
};

struct Process
{
  Process(const std::string &, int argc, char ** argv) {
    func(ptr(), ptr(), ptr(), ptr());
    std::string recent;
    std::string path = std::string("Hi!");
    recent           = std::string("Hi!");
    m_message        = std::string("Hi!");
    m_gui = new Gui(argc, argv);
  }
  ~Process()  { delete m_gui; }

  int exec(void) {
    return QMessageBox::warning(0, "Exit", "Sure?", QMessageBox::Ok);
  }

  void * ptr(void)  { return 0; }

  Gui       * m_gui;
  std::string m_message;
};

std::size_t strlen(const char * p) {
  std::size_t s = 0;
  while (*p++)
    s++;
  return s;
}

int main(int argc, char ** argv) {
  Process process("SomeString", argc, argv);
  return process.exec();
}

Rollback:

#0  0x0000000000400f13 in strlen (p=0x11 <Address 0x11 out of bounds>) at /home/alex/test/megaCrash/myprog.cpp:39
#1  0x0000003880a41922 in XSetCommand () from /usr/lib64/libX11.so.6
#2  0x0000003880a45fa6 in XSetWMProperties () from /usr/lib64/libX11.so.6
#3  0x00002aaaaad2e5ea in QWidgetPrivate::create_sys(unsigned long, bool, bool) () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#4  0x00002aaaaace735d in QWidget::create(unsigned long, bool, bool) () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#5  0x00002aaaaacef73a in QWidget::setVisible(bool) () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#6  0x00002aaaab11de5e in QDialog::setVisible(bool) () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#7  0x00002aaaab11d9e6 in QDialog::exec() () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#8  0x00002aaaab13bb40 in ?? () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#9  0x00002aaaab13bc7f in QMessageBox::warning(QWidget*, QString const&, QString const&, QFlags<QMessageBox::StandardButton>, QMessageBox::StandardButton) () from /usr/local/Trolltech/Qt-4.7.2/lib/libQtGui.so.4
#10 0x0000000000401514 in Process::exec (this=0x7fffffffe4e0) at /home/alex/test/megaCrash/myprog.cpp:27
#11 0x0000000000400fb6 in main (argc=1, argv=0x7fffffffe5f8) at /home/alex/test/megaCrash/myprog.cpp:47

, strlen. . p . Qt - . , . ? .

CMake :

cmake_minimum_required (VERSION 2.8) 

set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wall -Wno-unused-local-typedefs -fpic -fvisibility=hidden -m64")
set(CMAKE_CXX_FLAGS_DEBUG "${CMAKE_CXX_FLAGS_DEBUG} -ggdb -DDEBUG -gdwarf-2 -fstack-protector-all")
set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,-z,defs")

include_directories(${CMAKE_CURRENT_SOURCE_DIR})

find_package(Qt4 REQUIRED)
include(${QT_USE_FILE})

add_executable(myprog myprog.cpp)

target_link_libraries(myprog ${QT_LIBRARIES})

Qt - .

Answer 1

QApplication ( IMHO ) argc argv. . :

: , argc argv, QApplication. , argc , argv .

argc argv , undefined. , . , .