why do we delete target in RGWGetObjLayout constructed function?

why do we delete target in RGWGetObjLayout constructed function?

[liuchang0812]

I saw this problem when i read RGW source code. It seems that that
`delete` a nullptr will segment fault.

code[1]:

class RGWGetObjLayout : public RGWOp {
   protected:
        RGWRados::Object *target{nullptr};
        RGWObjManifest *manifest{nullptr};
        rgw_raw_obj head_obj;
    public:
         RGWGetObjLayout() {
             delete target;
   }


[1]. https://github.com/ceph/ceph/blob/master/src/rgw/rgw_op.h#L1777

Re: why do we delete target in RGWGetObjLayout constructed function?

[liuchang0812]

I crated a PR: https://github.com/ceph/ceph/pull/14014

2017-03-17 17:58 GMT+08:00 liuchang0812 <liuchang0812@gmail.com>:
> I saw this problem when i read RGW source code. It seems that that
> `delete` a nullptr will segment fault.
>
> code[1]:
>
> class RGWGetObjLayout : public RGWOp {
>    protected:
>         RGWRados::Object *target{nullptr};
>         RGWObjManifest *manifest{nullptr};
>         rgw_raw_obj head_obj;
>     public:
>          RGWGetObjLayout() {
>              delete target;
>    }
>
>
> [1]. https://github.com/ceph/ceph/blob/master/src/rgw/rgw_op.h#L1777

Re: why do we delete target in RGWGetObjLayout constructed function?

[liuchang0812]

yes, but target is not deleted.

2017-03-17 18:39 GMT+08:00 Jos Collin <jcollin@redhat.com>:
> No, it won't even if target = 0. As it is unused.
>
>
> On Friday 17 March 2017 03:28 PM, liuchang0812 wrote:
>
> I saw this problem when i read RGW source code. It seems that that
> `delete` a nullptr will segment fault.
>
> code[1]:
>
> class RGWGetObjLayout : public RGWOp {
>    protected:
>         RGWRados::Object *target{nullptr};
>         RGWObjManifest *manifest{nullptr};
>         rgw_raw_obj head_obj;
>     public:
>          RGWGetObjLayout() {
>              delete target;
>    }
>
>
>

Re: why do we delete target in RGWGetObjLayout constructed function?

[Matt Benjamin]

Hi,

Something looks funny, I'd agree.  However, for posterity, it's legal and therefore safe to delete (and free) nullptr.

Matt

----- Original Message -----
> From: "liuchang0812" <liuchang0812@gmail.com>
> To: "ceph-devel" <ceph-devel@vger.kernel.org>
> Sent: Friday, March 17, 2017 5:58:14 AM
> Subject: why do we delete target in RGWGetObjLayout constructed function?
> 
> I saw this problem when i read RGW source code. It seems that that
> `delete` a nullptr will segment fault.
> 
> code[1]:
> 
> class RGWGetObjLayout : public RGWOp {
>    protected:
>         RGWRados::Object *target{nullptr};
>         RGWObjManifest *manifest{nullptr};
>         rgw_raw_obj head_obj;
>     public:
>          RGWGetObjLayout() {
>              delete target;
>    }
> 
> 
> [1]. https://github.com/ceph/ceph/blob/master/src/rgw/rgw_op.h#L1777
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