使用new创建Qt QApplication时的分段错误

Question

我有一个程序,其中使用new运算符创建QApplication.它因未知原因而崩溃.我使用RedHat Linux,G ++ 4.8.2,Qt 4.7.2,它是用相同的编译器构建的.

这个源包含许多看似无用但无害的部分,例如带有四个未使用参数的'func'函数.如果我试图删除它们并进一步简化程序,则崩溃不再可以再现,这当然并不意味着问题已经解决.

崩溃发生在函数strlen中,该函数从系统函数XSetCommand调用.添加我自己的简单实现允许我看到strlen收到一个损坏的指针,见下文.

#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();
}

崩溃回溯:

#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

如你所见,它发生在strlen中.这就是我将自己的实现包含在内的原因.它的论点p指向无处.我尝试使用Qt的调试版本重现它 - 没有运气.这一切都让我觉得这里存在令人讨厌的记忆腐败.但它会在哪里发生？我这里只做无辜的事.

我用CMake来构建它:

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})

我试图在Qt文档和互联网中找到提示 - 没有运气.谢谢

Answer 1

QApplication有一个特殊的(恕我直言可疑)的要求argc和argv.查看文档:

警告: argc和argv引用的数据必须在QApplication对象的整个生命周期内保持有效.此外,argc必须大于零,并且argv必须至少包含一个有效的字符串.

如果argc和argv运行过程中被摧毁,发生不确定的行为.它可能在某些平台上运行,并且会在其他平台上崩溃.相应地更改您的代码并检查它是否修复了您的问题.