[cfe-commits] r115713 - in /cfe/trunk: lib/Sema/SemaType.cpp test/Sema/typeof-use-deprecated.c
John McCall
rjmccall at apple.com
Tue Oct 5 17:34:13 PDT 2010
On Oct 5, 2010, at 5:26 PM, jahanian wrote:
>
> On Oct 5, 2010, at 5:19 PM, John McCall wrote:
>
>>
>> On Oct 5, 2010, at 5:03 PM, jahanian wrote:
>>
>>>
>>> On Oct 5, 2010, at 4:52 PM, John McCall wrote:
>>>
>>>> On Oct 5, 2010, at 4:24 PM, Fariborz Jahanian wrote:
>>>>> Author: fjahanian
>>>>> Date: Tue Oct 5 18:24:00 2010
>>>>> New Revision: 115713
>>>>>
>>>>> URL: http://llvm.org/viewvc/llvm-project?rev=115713&view=rev
>>>>> Log:
>>>>> Issue deprecated warning when typeof uses an
>>>>> expression of deprecated type.
>>>>
>>>> This seems strange to me; deprecation warnings are usually based on how something is spelled, not what it actually resolves to. For example, even if a record type is deprecated, you can still make variables of that type if you have a non-deprecated typedef for it. So if the variable itself isn't deprecated, I'm not sure why getting its type with typeof is more suspect than any other use. Is there a specific use case motivating this?
>>>
>>> typeof is a gcc extension and I followed gcc's behavior. I guess it is because typeof is really a replacement for using
>>> the deprecated type directly. But I don't know more than that.
>>
>> Okay.
>>
>>>> There are a lot of subsidiary questions here, like whether we should warn in the following test cases:
>>>> deprecated_type *a; typeof(*a) b; // we now warn about this
>>>> deprecated_type *a; typeof(a) b; // but not about this
>>>> deprecated_typedef a; typeof(a) b; // or this
>>>
>>> gcc issues warnings on these but not for this, for example:
>>>
>>>> deprecated_type a[10]; typeof (a) b;
>>
>> Actually, as far as I can tell you've implemented the exact condition that gcc uses: it warns if the expression has a deprecated record or enum type, discarding typedefs and not looking through pointers/arrays/whatever.
>>
>>> So, I would say gcc's behavior is not consistent (I have access to 4.2 only though).
>>> But, I think we should warn in all cases (if we do for typeof ).
>>
>> I agree that if we want to warn here, we should at least warn about deprecated typedefs. But my preference would be to not warn here at all.
>
> Agreed. Actually, gcc does that too (please see my followup email).
I don't see this at all. gcc seems to look through typedefs and warn based on the underlying type's deprecatedness, unfortunately using the name of the typedef.
So this typeof produces a warning (misleadingly talking about 'bar'):
struct foo { int x; } __attribute__((deprecated));
typedef struct foo bar __attribute__((deprecated));
bar x;
int main() { typeof(x) y; }
But this one doesn't:
struct foo { int x; };
typedef struct foo bar __attribute__((deprecated));
bar x;
int main() { typeof(x) y; }
John.
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