开发 C++在指针地址的情况下给出不同的结果
我有以下一组代码
int main(){
int x = 36;
int const * p1;
p1 = &x;
printf("Values at p1: %d\n", *p1);
p1=0;
printf("Addresses pointed to by p1: %p ", &p1);
return 0;
}
给出
Addresses pointed to by p1 gives 0028FF480
int main(){
int x = 36;
int const * p1;
p1 = &x;
printf("Values at p1: %d\n", *p1);
p1=0;
printf("Addresses pointed to by p1: %p ", p1);
return 0;
}
p1 指向的地址给出 00000000
为什么会有这样的差异..？我认为两者都会给我相同的值。
I have a following set of codes
int main(){
int x = 36;
int const * p1;
p1 = &x;
printf("Values at p1: %d\n", *p1);
p1=0;
printf("Addresses pointed to by p1: %p ", &p1);
return 0;
}
gives
Addresses pointed to by p1 gives 0028FF480
int main(){
int x = 36;
int const * p1;
p1 = &x;
printf("Values at p1: %d\n", *p1);
p1=0;
printf("Addresses pointed to by p1: %p ", p1);
return 0;
}
Addresses pointed to by p1 gives 00000000
Why such a difference..?I thought both will give me same value.
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两者不同，因此输出也不同。
p1返回指针指向的变量的地址。&p1返回指针p1本身在内存中存储的地址。Both are different hence the difference in output.
p1returns the address of the variable pointed by the pointer.&p1returns the address where the pointerp1itself is stored in memory.最初，
p1存储x的地址（您通过&x获得）。稍后您设置p1来存储空地址。在第一个代码段中，您决定不打印
p1中存储的地址，而是打印p1的地址 本身。p1是一个与其他变量一样的变量，就像其他变量一样，&p1将为您提供该变量的地址。这与存储在其中的值不同，后者可以通过 p1 访问，并且是第二个片段打印的内容。与任何其他变量一样，您无法更改变量
p1的地址，您只能改变它存储的值，而对于指针来说，值恰好是一个地址。Initially
p1stores the address ofx(which you obtained with&x). Later on you setp1to store a null address.In the first snippet you decided to print not the address stored in
p1, but the address ofp1itself.p1is a variable like any other, and just like with the rest of them,&p1will give you the address of that variable. That's different from the value stored in it, which is accessible withp1and is what the second snippet prints.Like any other variable, you cannot change the address of the variable
p1, you can only change the value it stores, and in the case of a pointer it just so happens that value is an address.将把指向“p1”的指针设置为零，而不是它的内容，这应该由
will set the pointer that points to "p1" to zero, not the content of it which should be done by