c new delete

[xiliang_pan]

new 分配的 delete 不掉？

[xiliang_pan]

FILE *fp = NULL;
fp = fopen("C:\\1.txt","rb");
char *cert = NULL;
int len = -1,num = -1;
len = fseek(fp,0,SEEK_END);
num = ftell(fp);
cert = new char[len+1];
memset(cert,0,len+1);
len = fseek(fp,0,SEEK_SET);
//rewind(fp);
fread((void*)cert,sizeof(char),num,fp);
cert[num] = '\0';
OutputDebugString((char*)cert);
fclose(fp);
printf("%s\n",(char*)cert);
delete []cert; //报错 ？？？

[Zhentiwei]

贴出你代码看看啊
？

[sukyin]

怎么可能。

[dahua010]

len = fseek(fp,0,SEEK_END);
num = ftell(fp);
cert = new char[len+1];
memset(cert,0,len+1);
len = fseek(fp,0,SEEK_SET);
fread((void*)cert,sizeof(char),num,fp);

在上面这段代码中, LZ的cert 开辟的空间过小,所以fread((void*)cert,sizeof(char),num,fp)
对cert进行了越界的赋值操作.所以导致delete的时候崩溃

[sukyin]

你那个1.txt里面有东西没有？

[na_he]

delete t删除单个对象，
delete []t删除一组对象，如果定义了一组对象且不是内建类型，delete t只能删除一个对象，会造成内存泄漏

[Zhentiwei]

include <stdio.h>
#include <stdlib.h>
#include <iostream>
using namespace std;
int main()
{
	char *cert = NULL;
	int len = 9;
	cert = new char[len+1];
	cert[0] = 'a';
	cert[10] = 'a';
	cout<<cert<<endl;
	delete []cert;
	cout<<cert<<endl;
	return 0;
}

我这样也没有问题啊

[Zhentiwei]

／／FILE *fp = NULL;
／／fp = fopen("C:\\1.txt","rb");
char *cert = NULL;
int len = -1,num = -1;
／／len = fseek(fp,0,SEEK_END);
／／num = ftell(fp);
cert = new char[len+1];
／＊memset(cert,0,len+1);
len = fseek(fp,0,SEEK_SET);
//rewind(fp);
fread((void*)cert,sizeof(char),num,fp);
cert[num] = '\0';
OutputDebugString((char*)cert);
fclose(fp);
printf("%s\n",(char*)cert);
＊／
delete []cert;  //报错 ？

调试看看

[xiliang_pan]

对cert分配的空间不足时，fread对其越界赋值后delete只是释放为cert分配的空间，为什么会试图
释放掉其他空间？

[dahua010]

这个具体也不好解释.只能说下个人理解.

指针本身也不会知道自己的空间大小,分配的空间应该有一个标志,而越界赋值则破坏了那个标志,从而会导致释放出错.

以上是个人理解,如果不对,还请高人来解答