[cfe-commits] r115713 - in /cfe/trunk: lib/Sema/SemaType.cpp test/Sema/typeof-use-deprecated.c

[John McCall]

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.

John.