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Subject: Re: V10 [PATCH] C/C++: Add -Waddress-of-packed-member
To: "H.J. Lu" <hjl.tools@gmail.com>
Cc: Sandra Loosemore <sandra@codesourcery.com>, Richard Guenther <richard.guenther@gmail.com>, "Joseph S. Myers" <joseph@codesourcery.com>, Martin Sebor <msebor@gmail.com>, GCC Patches <gcc-patches@gcc.gnu.org>
References: <CAMe9rOohUOR+eta2gvwNxbjMR1y=P=vA3+Sniaj_tS03qamj6g@mail.gmail.com> <d3a6bf60-4c66-54d7-b159-a6f6b5ecfdbe@redhat.com> <CAMe9rOq67grqBtdDL7YQdAwGp+9KAqiuQbs_gyiXdemNoX19Ng@mail.gmail.com> <24f8a201-bb3e-3acb-b679-570a8796358d@redhat.com> <CAMe9rOo1hsE9pMC5DV1t0LJ0xkKhdX7TACf1_pZpYmxaNgZMPA@mail.gmail.com> <CAFiYyc2JrHbXA5QNuXqyRzccnzwf9iduSZBJBw8A_fOSMHMPaw@mail.gmail.com> <CAMe9rOq93B0tO_SkJ=aPP4rYfDG8pf4+_-7WhKy60mn5PCrEZw@mail.gmail.com> <bd7ff807-0918-9d66-8043-969d4d2ff8b0@redhat.com> <20181218141051.GA3461@gmail.com> <14946d45-0983-12ad-3f93-99da07b3886e@redhat.com> <CAMe9rOq-_k1ntkAxbDCKY=OdFrzdS+Z6b_MZdVOwWRTFCP4_Mg@mail.gmail.com> <7f0ae96e-87b8-5db9-97b5-90094c4dace7@redhat.com> <CAMe9rOq+Smwo+LWTE=ygPH0kMOCdTYNh9FOHWoWSjJv4g=ccNw@mail.gmail.com> <CAMe9rOomWf5=+_mtgqNdTwq2V3uSgStcraLX57Nc-uLJsyvO=A@mail.gmail.com> <63472b60-a401-5c43-de38-87187cdc95c5@redhat.com> <CAMe9rOqyBw4ZeE6-UQExRe0mEx+PrUCn3oDWZz2Dn5Lv01h-uA@mail.gmail.com>
From: Jason Merrill <jason@redhat.com>
Message-ID: <a4292d4c-8e9c-5780-9a52-63b9b1630beb@redhat.com>
Date: Thu, 20 Dec 2018 21:31:00 -0000
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On 12/20/18 2:52 PM, H.J. Lu wrote:
> On Thu, Dec 20, 2018 at 11:28 AM Jason Merrill <jason@redhat.com> wrote:
>>
>> On 12/19/18 12:35 PM, H.J. Lu wrote:
>>> +  while (handled_component_p (rhs))
>>> +    {
>>> +      if (TREE_CODE (rhs) == COMPONENT_REF)
>>> +     break;
>>> +      rhs = TREE_OPERAND (rhs, 0);
>>> +    }
>>> +
>>> +  if (TREE_CODE (rhs) != COMPONENT_REF)
>>> +    return NULL_TREE;
>>> +
>>> +  object = TREE_OPERAND (rhs, 0);
>>> +  field = TREE_OPERAND (rhs, 1);
>>> +
>>> +  tree context = check_alignment_of_packed_member (type, field);
>>> +  if (context)
>>> +    return context;
>>
>> All the above looks unnecessary; it will be handled by the loop below.
>>
>>> +  /* Check alignment of the object.  */
>>> +  while (handled_component_p (object))
>>> +    {
>>> +      if (TREE_CODE (object) == COMPONENT_REF)
>>> +     {
>>> +       do
>>> +         {
>>> +           field = TREE_OPERAND (object, 1);
>>> +           context = check_alignment_of_packed_member (type, field);
>>> +           if (context)
>>> +             return context;
>>> +           object = TREE_OPERAND (object, 0);
>>> +         }
>>> +       while (TREE_CODE (object) == COMPONENT_REF);
>>
>> This inner loop also seems unnecessary.
>>
>>> +     }
>>> +      else
>>> +     object = TREE_OPERAND (object, 0);
>>> +    }
>>
>> Jason
> 
> I changed it to
> 
> static tree
> check_address_of_packed_member (tree type, tree rhs)
> {
>    if (INDIRECT_REF_P (rhs))
>      rhs = TREE_OPERAND (rhs, 0);
> 
>    if (TREE_CODE (rhs) == ADDR_EXPR)
>      rhs = TREE_OPERAND (rhs, 0);
> 
>    tree context = NULL_TREE;
> 
>    /* Check alignment of the object.  */
>    while (handled_component_p (rhs))
>      {
>        if (TREE_CODE (rhs) == COMPONENT_REF)
>          {
>            tree field = TREE_OPERAND (rhs, 1);
>            context = check_alignment_of_packed_member (type, field);
>            if (context)
>              break;
>          }
>        rhs = TREE_OPERAND (rhs, 0);
>      }
> 
>    return context;
> }
> 
> Here is the updated patch.  OK for trunk?

OK.

Jason