小编Viv*_*ran的帖子

以下是代码，我将其作为参考，以了解{}函数中存在的子作用域（或）虚拟作用域（仅）如何影响堆栈帧的结构。

#include <stdio.h>
int main()
{
   int main_scope=0; /*Scope and life time of the variable is throughout main*/

   {
     //From below two statements I assume that there
     //is no seperate "stack frame" created for just
     //braces {}.So we are free access (scope exists) and
     //modify (lifetime exists) the variable "main_scope"
     //anywhere within main

     main_scope++;
     printf("main_scope++:(%d)\n",main_scope);

    //I expected this statement to throw an error saying
    //"Multiple definition for "main_scope".But it isn't????

    int main_scope=2;
    printf("Value of redefined main_scope:(%d)\n",main_scope);

  }

  printf("Finally …

当我浏览手册页时shmat.它被描述为API的原始函数是将与其关联的内存段附加shmid到调用进程的地址空间.

我的问题如下.

• 术语附件对我来说是通用的.我发现很难理解附着所指的基本活动是什么.
• 通过映射一段内存意味着什么？

请考虑以下代码

#include <stdio.h>
#define ROW_SIZE 2
#define COL_SIZE 2

int main()
{
   int a[ROW_SIZE][COL_SIZE]={{1,2},{3,4}};

   // Base address:Pointer to the first element a 1D array
   printf("Base address of array:%p\n",a);

   //The value at the base address: should be the address of 1st 1D array
   printf("Value at the Base address:%p\n",*a);

   return 0;
}

获得的产出:

Sample Output:
Base address of array:0xbff77434
Value at the Base address:0xbff77434

不知何故,我无法理解2D数组的基地址的概念和基地址的值,该地址是1D数组的地址相同.请解释.

以下代码导致内存损坏导致崩溃.我假设这是因为delete pTestStateMachine试图删除未在堆中分配的内存.那是对的吗？

如果是这样,是否意味着QStateMachine::addState(QAbstractState * state)必须始终传递动态分配的内存？不幸的是Qt docs并没有指定任何这样的条件.我在这里错过了什么？

class CTestClass
{
public:
    QState m_pTestState;
};

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    QStateMachine *pTestStateMachine;
    CTestClass  TestClass;

    pTestStateMachine = new QStateMachine();
    pTestStateMachine->addState(&(TestClass.m_pTestState));
    pTestStateMachine->setInitialState(&(TestClass.m_pTestState));
    pTestStateMachine->start();

    pTestStateMachine->stop();
    delete pTestStateMachine;

    return a.exec();
}