D******4
发帖数: 47 | 1 今天看到dynamic memory，测试如下程序：
#include
#include
#include
using namespace std;
ifstream fin("test.in");
ofstream fout("test.out");
int main (){
int i = 0;
int n = 0;
int* p;
if(fin.is_open()){
fin>>n;
fout<<"n is: "<
p = new (nothrow) int[n];
if (p == 0)
fout << "Error: memory could not be allocated"<
else{
for (i=0; i> p[i];
fin.close();
fout << "You have ent |
j******n
发帖数: 271 | 2 new T[0];
is allowed. But result of dereferencing the returned is undefined. |
D******4
发帖数: 47 | 3 多谢了哈
我在其他地方也得到一些回复，也贴在这吧。
new int[0]是可以的，当内存足够时，会返回非空指针，且这样new两次仍然会返回不同
的指针。
ISO/IEC 14882:1998(E) 5.3.4p7:
When the value of the expression in a direct-new-declarator is zero, the
allocation function is called to allo-
cate an array with no elements. The pointer returned by the new-
expression
is non-null. [Note: If the
library allocation function is called, the pointer returned is distinct
from the pointer to any other object.
这与malloc不同，malloc(0)也是可以的，但返回的是空指针，这并不表示出现了内存
用尽等异常情况。
最新的标准有了一些小的改
【在 j******n 的大作中提到】
: new T[0];
: is allowed. But result of dereferencing the returned is undefined.
|
