[c++基础] const char and static const char

部分内容摘自：https://blog.csdn.net/ranhui_xia/article/details/32696669

The version with const char * will copy data from a read-only location to a variable on the stack.

The version with static const char * references the data in the read-only location (no copy is performed).

在函数内部，const char *每次调用函数时，都需要在stack上分配内存，然后将数据拷贝过来，函数退出前释放。

而static const char *，会直接访问read only的数据，无需再stack上分配内存。

char * const cp     : 定义一个指向字符的指针常数，即const指针

const char* p       : 定义一个指向字符常数的指针

char const* p       : 等同于const char* p

举个例子：

#include <iostream>
#include <cstdio>
using namespace std;

int main()
{
    char ch[3] = {'a','b','c'};
    char* const cp = ch;
    printf("char* const cp: 
 %c
", *cp);
    /* 
    ** cp point to a fixed address
    **
    cp++;  //error: increment of read-only variable ‘cp’
    printf("char* const cp: 
 %c
", *cp);
    **
    */

    const char ca = 'a';
    const char* p1 = &ca;

    /* 
    ** 2. Only const char* pointer can point to a const char
    **
    const char cb = 'b';
    char* p2 = &cb; //error: invalid conversion from ‘const char*’ to ‘char*’
    **
    **/

    /*
    ** 3. p1 points to a const char, the char be pointed has to be const, 
    **    p1 can point to a different const char
    */ 
    printf("const char* p1: 
 %c
", *p1);
    const char cb = 'b';
    p1 = &cb;
    printf(" %c
", *p1);
    return 0;
}

/*
** Output:
char* const cp: 
 a
const char* p1: 
 a
 b
**
*/