C + + Reference essence of Understanding ①

//referential nature of understanding ①#include <iostream>using namespacestd;intGeta () {intA =Ten; returnA;}int&Getb () {intA =Ten; printf ("the address of a is%x\n", &a); returnA;}voidMain () {intA1 =Ten, a2 =0; A1=Geta (); printf ("the value of A1 is%d\n", A1); //Print Ten//After careful observation of the memory discovery return A; the C + + compiler did not immediately destroy the memory space identified by a after the sentence was executed.//instead of executing a1 = Geta (), the memory space is not destroyed after this copy operation//so the variable A1 can accept the value of local variable A to print 10 is not accidental success A2=Getb (); //Pre-description int &b=a; //A reference is essentially a constant pointer B is a pointer, but a reference to pointer B's memory space cannot be changed//C+ + compiler internal completion is ① create an int * const type of constant pointer b      //② assigns the address of variable A to the constant pointer b//when the C + + compiler discovers that there is an operation that requires a value or assignment to (reference pointer) b, the//c++ compiler defaults to B for a fetch *P operation----This is the C + + compiler internal behavior (so C + + will be so slow to do a lot of stealth)//For example printf ("b=%d\n", b);    This is essentially printf ("b=%d\n", *b); //another example b=20;    essentially a *b=20; // again, the default pointer extraction * operation is only a special treatment of C + + reference pointers ; C + + compiler does not default to other pointers * Operation//so let's analyze the function Getb ()//when Getb () return A; is equal to the C + + compiler defines a temporary reference pointer temp//assigns the address of variable A to the temporary reference pointer temp//Execution a2 = Getb ();       is actually executing a2=*temp; //After careful observation found return a; the C + + compiler did not immediately destroy the memory space identified by a after the sentence was executed.//instead of executing a2 = GETB (); The memory space of local variable A is not destroyed after this copy operation//so the a2=*temp at this time; Fully effective//the "=" assignment operation is to copy the value of the local variable A into the memory space identified by the A2printf ("A2 's address is%x\n.", &AMP;A2);//Print a4f754printf"the value of A2 is%d\n", a2);//Print Ten        int&AMP;A3 =Getb (); //likewise for int &a3 = GETB ();    You can essentially write int &a3=*temp; //at this point the *temp is a value because the memory space of local variable A is not released because it executes to int &a3 = GETB ();//Define int &a3=*temp; Then the C + + compiler assigns the *temp address to the reference pointer A3 (A3=TEMP;), which assigns the value of the pointer temp to the pointer A3 //the value of reference pointer temp is also &a (address of a)//when performing printf ("A3 value is%d\n", A3);     Essentially the execution of printf ("A3 value is%d\n", *a3); //but int &a3 = GETB (); The memory space of local variable A is freed after execution is complete .//The data for the memory space pointed to by temp has been reset by the system, so the *temp data can only be dirty data and A3 is equal to temp.//so *A3 data is also dirty data.printf ("A3 's address is%x\n.", &AMP;A3);//Print a4f664 At this point the address of local variable A is also a4f664printf"the value of A3 is%d\n", A3);//Dirty DataSystem"Pause");}

C + + Reference essence of Understanding ①