小程序，容器中的指针地址到底是什么？

程序如下：

class Obj
{
public:
Obj( bool b )
{
m_bAlive = b;
}

BOOL IsAlive()
{
return m_bAlive;
}

private:
bool m_bAlive;
};


list < Obj* > arr;


void del( Obj* &p )
{
delete p;
}

void print( Obj* &p )
{
if( p )
cout < < p < < " ";
else
cout < < "00000000 ";
}

void del_ptr( Obj* &p )
{
if( p-> IsAlive() )
return;

delete p;
}


void func1()
{
arr.push_back( new Obj( true ) );
arr.push_back( new Obj( true ) );
arr.push_back( new Obj( true ) );
arr.push_back( new Obj( false ) );
arr.push_back( new Obj( false ) );


for_each( arr.begin(), arr.end(), print );
cout < < endl;

// 首先删除对象值为false的指针
for_each( arr.begin(), arr.end(), del_ptr );//（！问题！）

for_each( arr.begin(), arr.end(), print );
cout < < endl;


list < Obj* > ::iterator _end;

// 然后删除迭代器
_end = remove( arr.begin(), arr.end(), (Obj*)0 );
arr.erase( _end, arr.end() );

for_each( arr.begin(), arr.end(), print );cout < < endl;

for_each( arr.begin(), arr.end(), del );
}

无论三个函数的参数是Obj* p还是Obj* &p，在for_each( arr.begin(), arr.end(), del_ptr )这一句都会出现问题，对象被删除了，但是下一次仍然能看到那个地址。

当然，可以通过下列方法实现：


list < Obj* > ::iterator iter;

for( iter = arr.begin(); iter != arr.end(); )
{
if( ( *iter )-> IsAlive() )
{
iter++;
continue;
}

delete *iter;
*iter = 0;
iter = arr.erase( iter );
}

那么通过算法传到函数中的地址显然并不是真正的对象地址，今早一个大牛同事也没解释出啥来，还请大家帮忙解释一下，谢谢！

[解决办法]
指针所指的内存被释放，但是指针所指的地址仍然不变,只是把指针所指的内存给释放掉，但并没有把指针本身干掉。
[解决办法]
同意楼上意见.

对你的程序,包括那行.
// 首先删除对象值为false的指针
for_each( arr.begin(), arr.end(), del_ptr );//（！问题！）

内存被正确的释放乐, 但是指针所指的地址仍然不变,只是把指针所指的内存给释放掉，但并没有把指针本身干掉。

我用valgrind 查了一下内存, 没有leak.

[gx150-49]~/temp> valgrind --tool=memcheck --leak-check=yes ./a.out
==4978== Memcheck, a memory error detector for x86-linux.
==4978== Copyright (C) 2002-2005, and GNU GPL 'd, by Julian Seward et al.
==4978== Using valgrind-2.4.0, a program supervision framework for x86-linux.
==4978== Copyright (C) 2000-2005, and GNU GPL 'd, by Julian Seward et al.
==4978== For more details, rerun with: -v
==4978==
0x1b92b028 0x1b92c368 0x1b92c3a0 0x1b92c3d8 0x1b92c410

==4978==
==4978== ERROR SUMMARY: 0 errors from 0 contexts (suppressed: 16 from 1)
==4978== malloc/free: in use at exit: 4461 bytes in 11 blocks.
==4978== malloc/free: 13 allocs, 2 frees, 4463 bytes allocated.
==4978== For counts of detected errors, rerun with: -v
==4978== searching for pointers to 11 not-freed blocks.
==4978== checked 106856 bytes.
==4978==
==4978== LEAK SUMMARY:
==4978== definitely lost: 0 bytes in 0 blocks.
==4978== possibly lost: 0 bytes in 0 blocks.
==4978== still reachable: 4461 bytes in 11 blocks.
==4978== suppressed: 0 bytes in 0 blocks.
==4978== Reachable blocks (those to which a pointer was found) are not shown.
==4978== To see them, rerun with: --show-reachable=yes
[解决办法]
void del_ptr( Obj* &p )
{
if( p-> IsAlive() )
return;

delete p;
}
这个改为
void del_ptr( Obj& *p )
{
if( p-> IsAlive() )
return;
delete p;
p = 0;
}
[解决办法]
delete p;
p = 0;