C++编程中指针的声明与基本使用讲解

[storage-class-specifiers] [cv-qualifiers] type-specifiers 
[ms-modifier] declarator ;

* [cv-qualifiers] identifier [= expression]

(* [cv-qualifiers] identifier )( argument-list ) [cv-qualifers]
[exception specification] [= expression];

* identifier [ [ constant-expression ] ]

char *pch;

static unsigned int * const ptr;

static int *p = &i, *q = &j;

// pointer.cpp
// compile with: /EHsc
#include <iostream>
int main() {
 int i = 1, j = 2; // local variables on the stack
 int *p;

 // a pointer may be assigned to "point to" the value of
 // another variable using the & (address of) operator
 p = & j; 

 // since j was on the stack, this address will be somewhere
 // on the stack. Pointers are printed in hex format using
 // %p and conventionally marked with 0x. 
 printf_s("0x%p\n", p);

 // The * (indirection operator) can be read as "the value
 // pointed to by".
 // Since p is pointing to j, this should print "2"
 printf_s("0x%p %d\n", p, *p);

 // changing j will change the result of the indirection
 // operator on p.
 j = 7;
 printf_s("0x%p %d\n", p, *p );

 // The value of j can also be changed through the pointer
 // by making an assignment to the dereferenced pointer
 *p = 10;
 printf_s("j is %d\n", j); // j is now 10

 // allocate memory on the heap for an integer,
 // initialize to 5
 p = new int(5);

 // print the pointer and the object pointed to
 // the address will be somewhere on the heap
 printf_s("0x%p %d\n", p, *p);

 // free the memory pointed to by p
 delete p;

 // At this point, dereferencing p with *p would trigger
 // a runtime access violation.

 // Pointer arithmetic may be done with an array declared
 // on the stack or allocated on the heap with new.
 // The increment operator takes into account the size 
 // of the objects pointed to.
 p = new int[5];
 for (i = 0; i < 5; i++, p++) {
 *p = i * 10;
 printf_s("0x%p %d\n", p, *p);
 }

 // A common expression seen is dereferencing in combination
 // with increment or decrement operators, as shown here.
 // The indirection operator * takes precedence over the 
 // increment operator ++. 
 // These are particularly useful in manipulating char arrays.
 char s1[4] = "cat";
 char s2[4] = "dog";
 char* p1 = s1;
 char* p2 = s2;

 // the following is a string copy operation
 while (*p1++ = *p2++);

 // s2 was copied into s1, so now they are both equal to "dog"
 printf_s("%s %s", s1, s2);
}

0x0012FEC8
0x0012FEC8 2
0x0012FEC8 7
j is 10
0x00320850 5
0x00320850 0
0x00320854 10
0x00320858 20
0x0032085C 30
0x00320860 40
dog dog

// pointer_linkedlist.cpp
// compile with: /EHsc
#include <iostream>
using namespace std;

struct NewNode {
 NewNode() : node(0){}
 int i;
 NewNode * node;
};

void WalkList(NewNode * ptr) {
 if (ptr != 0) {
 int i = 1;
 while (ptr->node != 0 ) {
  cout << "node " << i++ << " = " << ptr->i << endl;
  ptr = ptr->node;
 }
 cout << "node " << i++ << " = " << ptr->i << endl;
 }
}

void AddNode(NewNode ** ptr) {
 NewNode * walker = 0;
 NewNode * MyNewNode = new NewNode;
 cout << "enter a number: " << endl;
 cin >> MyNewNode->i;

 if (*ptr == 0)
 *ptr = MyNewNode;
 else {
 walker = *ptr;
 while (walker->node != 0)
  walker = walker->node;

 walker->node = MyNewNode;
 }
}

int main() {
 char ans = ' ';
 NewNode * ptr = 0;
 do {
 cout << "a (add node) d (display list) q (quit)" << endl;
 cin >> ans;
 switch (ans) {
 case 'a':
  AddNode(&ptr);
  break;
 case 'd':
  WalkList(ptr);
  break;
 }
 } while (ans != 'q');
}

a
45
d
a
789
d
qa (add node) d (display list) q (quit)
enter a number:
a (add node) d (display list) q (quit)
node 1 = 45
a (add node) d (display list) q (quit)
enter a number:
a (add node) d (display list) q (quit)
node 1 = 45
node 2 = 789
a (add node) d (display list) q (quit)

const char *cpch;
volatile char *vpch;

char * const pchc;
char * volatile pchv;

const char cch = 'A';
char ch = 'B';

const char *pch1 = &cch;
const char *const pch4 = &cch;
const char *pch5 = &ch;
char *pch6 = &ch;
char *const pch7 = &ch;
const char *const pch8 = &ch;

char *pch2 = &cch;  // Error
char *const pch3 = &cch;  // Error

*pch1 = 'A'; // Error: object declared const
pch1 = &ch;  // OK: pointer not declared const
*pch2 = 'A'; // OK: normal pointer
pch2 = &ch;  // OK: normal pointer
*pch3 = 'A'; // OK: object not declared const
pch3 = &ch;  // Error: pointer declared const
*pch4 = 'A'; // Error: object declared const
pch4 = &ch;  // Error: pointer declared const

errno_t strcpy_s( char *strDestination, size_t numberOfElements, const char *strSource );

// const_pointer.cpp
int *const cpObject = 0;
int *pObject;

int main() {
pObject = cpObject;
cpObject = pObject;  // C3892
}

// const_pointer2.cpp
struct X {
  X(int i) : m_i(i) { }
  int m_i;
};

int main() {
  // correct
  const X cx(10);
  const X * pcx = &cx;
  const X ** ppcx = &pcx;

  // also correct
  X const cx2(20);
  X const * pcx2 = &cx2;
  X const ** ppcx2 = &pcx2;
}