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Re: [PATCH] Avoid warning when unused attribute applied to C++ member variables (issue8212043)
- From: Teresa Johnson <tejohnson at google dot com>
- To: Andrew Pinski <pinskia at gmail dot com>
- Cc: "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>, reply at codereview dot appspotmail dot com
- Date: Sun, 31 Mar 2013 09:39:46 -0700
- Subject: Re: [PATCH] Avoid warning when unused attribute applied to C++ member variables (issue8212043)
- References: <20130331071036 dot A877C807B2 at tjsboxrox dot mtv dot corp dot google dot com> <CA+=Sn1mCLwiw3oPt9oP+WM7H1KxdOKqfwMGBvaLAyhLSh+G60A at mail dot gmail dot com>
On Sun, Mar 31, 2013 at 1:36 AM, Andrew Pinski <pinskia@gmail.com> wrote:
> On Sun, Mar 31, 2013 at 12:10 AM, Teresa Johnson <tejohnson@google.com> wrote:
>> This patch allows the unused attribute to be used without warning
>> on C++ class members, which are of type FIELD_DECL. This is for
>> compatibility with clang, which allows the attribute to be specified on
>> class members and struct fields. It looks like more work would need to
>> be done to implement the actual unused variable detection and warning
>> on FIELD_DECLs, but this change will at least avoid the warning on the
>> code that uses the unused attribute in these cases. The documentation at
>> http://gcc.gnu.org/onlinedocs/gcc/Variable-Attributes.html also doesn't
>> seem to preclude its use on C++ member variables.
>
> This also allows it on field in normal C case. As far as I understand
> they are fields and not variables in the normal programming sense
> which is why the document does not mention them.
That's true that this change will also allow the unused attribute on
normal C struct fields. I just verified that clang also allows this,
and it could potentially be taken advantage of to warn on unused
fields as well.
Teresa
>
> Thanks,
> Andrew Pinski
>
>
>>
>> Bootstrapped and tested on x86-64-unknown-linux-gnu. Ok for trunk?
>>
>> 2013-03-30 Teresa Johnson <tejohnson@google.com>
>>
>> * c-family/c-common.c (handle_unused_attribute): Handle
>> FIELD_DECL for C++ class members.
>>
>> Index: c-family/c-common.c
>> ===================================================================
>> --- c-family/c-common.c (revision 197266)
>> +++ c-family/c-common.c (working copy)
>> @@ -6753,6 +6753,7 @@ handle_unused_attribute (tree *node, tree name, tr
>>
>> if (TREE_CODE (decl) == PARM_DECL
>> || TREE_CODE (decl) == VAR_DECL
>> + || TREE_CODE (decl) == FIELD_DECL
>> || TREE_CODE (decl) == FUNCTION_DECL
>> || TREE_CODE (decl) == LABEL_DECL
>> || TREE_CODE (decl) == TYPE_DECL)
>>
>> --
>> This patch is available for review at http://codereview.appspot.com/8212043
--
Teresa Johnson | Software Engineer | tejohnson@google.com | 408-460-2413