程序中变量的内存安排和const_cast问题

结论：

【1】const_cast可以转换栈和堆中的const，但对静态存储区中的const无能为力。

【2】bss段的排布顺序是： 1）全局non-static未初始化变量；2）全局static未初始化变量；3）局部static未初始化变量

【3】data数据段的排布规则是：1）全局已初始化变量，不分是否static，只按声明顺序；2）局部static已初始化变量。

【4】const全局变量（const；static const）或局部static const 变量放在一起，位于【3】之前，是只读区，排列顺序是：1）全局const或static const变量（不区分是否static）；2）局部static const变量。

从低到高依次是【4】、【3】、【2】、堆、栈

PS：另外，测试代码没有体现的是，在栈中，如果没有函数调用，只是if{}或者{}或者while{}，那么是不会重新开启一块堆栈的，分配依然会在原有地址基础上向上扩展，只有函数调用才会新建栈帧。

测试代码：

#include <iostream>
using namespace std;

int ig1=8;
int ig2=8;
const int igc1=6;
const int igc2=6;
static const int igcs1=7;
static const int igcs2=7;
static int igs1=9;
static int igs2=9;

int ig3=8;
const int igc3=6;
static const int igcs3=7;
static int igs3=9;

int g1;
int g2;
static int gs1;
static int gs2;
int g3;
static int gs3;

int main()
{
int y1=3;
int y2=3;
const int cy1=4;
const int cy2=4;
static int sy1=5;
static int sy2=5;
static int nsy1;
static int nsy2;
static const int scy1=2;
static const int scy2=2;

int y3=3;
const int cy3=4;
static int sy3=5;
static int nsy3;
static const int scy3=2;

{
int ly1=3;
const int cly1=3;
int ly2=3;
const int cly2=cly1;
const int cly3=cly1;
int ly3=3;
/*
// {}
cout<<"ly1= "<<ly1<<" "<<&ly1<<endl;
cout<<"ly2= "<<ly2<<" "<<&ly2<<endl;
cout<<"ly3= "<<ly3<<" "<<&ly3<<endl;
cout<<"cly1= "<<cly1<<" "<<&cly1<<endl;
cout<<"cly2= "<<cly2<<" "<<&cly2<<endl;
cout<<"cly3= "<<cly3<<" "<<&cly3<<endl;
*/  }

/*
//main
cout<<"y1= "<<y1<<" "<<&y1<<endl;
cout<<"y2= "<<y2<<" "<<&y2<<endl;
cout<<"y3= "<<y3<<" "<<&y3<<endl;
cout<<"cy1= "<<cy1<<" "<<&cy1<<endl;
cout<<"cy2= "<<cy2<<" "<<&cy2<<endl;
cout<<"cy3= "<<cy3<<" "<<&cy3<<endl;

cout<<"sy1= "<<sy1<<" "<<&sy1<<endl;
cout<<"sy2= "<<sy2<<" "<<&sy2<<endl;
cout<<"sy3= "<<sy3<<" "<<&sy3<<endl;
cout<<"scy1= "<<scy1<<" "<<&scy1<<endl;
cout<<"scy2= "<<scy2<<" "<<&scy2<<endl;
cout<<"scy3= "<<scy3<<" "<<&scy3<<endl;

// g
cout<<"g1= "<<g1<<" "<<&g1<<endl;
cout<<"g2= "<<g2<<" "<<&g2<<endl;
cout<<"g3= "<<g3<<" "<<&g3<<endl;

cout<<"gs1= "<<gs1<<" "<<&gs1<<endl;
cout<<"gs2= "<<gs2<<" "<<&gs2<<endl;
cout<<"gs3= "<<gs3<<" "<<&gs3<<endl;

cout<<"ig1= "<<ig1<<" "<<&ig1<<endl;
cout<<"ig2= "<<ig2<<" "<<&ig2<<endl;
cout<<"ig3= "<<ig3<<" "<<&ig3<<endl;
cout<<"igc1= "<<igc1<<" "<<&igc1<<endl;
cout<<"igc2= "<<igc2<<" "<<&igc2<<endl;
cout<<"igc3= "<<igc3<<" "<<&igc3<<endl;
cout<<"igs1= "<<igs1<<" "<<&igs1<<endl;
cout<<"igs2= "<<igs2<<" "<<&igs2<<endl;
cout<<"igs3= "<<igs3<<" "<<&igs3<<endl;
cout<<"igcs1= "<<igcs1<<" "<<&igcs1<<endl;
cout<<"igcs2= "<<igcs2<<" "<<&igcs2<<endl;
cout<<"igcs3= "<<igcs3<<" "<<&igcs3<<endl;

cout<<"nsy1= "<<nsy1<<" "<<&nsy1<<endl;
cout<<"nsy2= "<<nsy2<<" "<<&nsy2<<endl;
cout<<"nsy3= "<<nsy3<<" "<<&nsy3<<endl;
*/
int *p1=new int;
const int *p2=new int;
int *const p3=new int[3];

cout<<"p1= 1 "<<p1<<endl;
cout<<"p2= 1 "<<p2<<endl;
cout<<"p3= 1 "<<p3<<endl;

int *p;
p = const_cast<int*>(&cy1); // 栈的const
*p=9; cout<<*p<<endl;

//   p=const_cast<int*>(&igcs1); *p=9;  cout<<*p<<endl;//全局，static const.编译通过，运行段错误
//  p=const_cast<int*>(&igc1); *p=9; cout<<*p<<endl; //全局，static const。编译通过，运行段错误
//   p=const_cast<int*>(&scy1); *p=9; cout<<*p<<endl; //局部，static const。编译通过，运行段错误
p=const_cast<int*>(p2); *p=9;  cout<<*p<<endl;//堆中 const int *
p=const_cast<int*>(p3); p=&ig1;  cout<<*p<<endl; //堆中 const *int

delete p1;
delete p2;
delete []p3;
return 0;
}