[cfe-commits] [PATCH] Laying the foundation for alternate C++ ABI support

[Fariborz Jahanian]

On May 25, 2010, at 1:34 PM, Douglas Gregor wrote:

>
> On May 25, 2010, at 1:33 PM, John McCall wrote:
>
>>
>> On May 25, 2010, at 12:56 PM, Douglas Gregor wrote:
>>
>>>
>>> On May 25, 2010, at 12:54 PM, Charles Davis wrote:
>>>
>>>> On 5/25/10 11:18 AM, John McCall wrote:
>>>>> On May 24, 2010, at 10:43 PM, Charles Davis wrote:
>>>>>> This is the first patch in my GSoC series, in which I will  
>>>>>> factor out
>>>>>> C++ ABI support in IRgen so that we can support other C++ ABIs.  
>>>>>> This
>>>>>> patch is very simple. It just adds a class hierarchy similar to  
>>>>>> the one
>>>>>> for Objective-C runtimes, and a basic implementation for the  
>>>>>> current GNU
>>>>>> C++ ABI. All it supports is name mangling. CodeGenFunction has  
>>>>>> been
>>>>>> redirected to use this new interface instead of holding the
>>>>>> MangleContext itself (which is very specific to the GNU ABI  
>>>>>> right now).
>>>>>
>>>>> For better or worse, people call this the Itanium ABI;  gcc's  
>>>>> implementation hews
>>>>> faithfully to that standard, and we should use that name.  The  
>>>>> term "GNU ABI" is likely
>>>>> to make people think of the old (pre-v3.2) gcc ABI.
>>>> Noted.
>>>>>
>>>>> Also, I think we can live without the "CG" prefix on "CGCXXABI".
>>>> Done. (The header name still has the CG prefix, though.)
>>>>>
>>>>> I'd prefer to avoid lazy initialization.  We should never be  
>>>>> calling into the
>>>>> CXXABI for non-C++ code, so you should be able to create it  
>>>>> during initialization
>>>>> if CPlusPlus is set and then assert on its existence in  
>>>>> getCXXABI().
>>>> I don't know about that.
>>>>
>>>> When I added the assert, clang started asserting whenever it was
>>>> generating IR for non-C++ (that's C and ObjC) code. I think clang  
>>>> right
>>>> now just assumes that the MangleContext is always available and  
>>>> will "Do
>>>> the Right Thing" based on whether or not Features.CPlusPlus is set.
>>>>
>>>> I agree, C and ObjC IRgen shouldn't be calling into any C++- 
>>>> specific
>>>> stuff. But I'll fix that later.
>>>
>>>
>>> We use the "C++" mangler for some things in C/Objective-C as well,  
>>> including blocks (a recent change), overloaded functions in C, and  
>>> (IIRC) some Objective-C method names.
>>
>> Ah, right, I'd forgotten about that.  So yeah, we should continue  
>> to lazily create the C++ ABI.
>>
>> I suppose it's reasonable to always defer these manglings to the  
>> target C++ ABI.  Maybe we can abstract out some common  
>> functionality so that new ABIs don't need so many redundant  
>> manglings.
>
> Yes, I think that makes sense. Separating ObjC from C++ might be  
> reasonable, for example.

ObjC does not do any C++ style mangling (ObjC's type encoding is in  
ASTContext.cpp).  Blocks are part of all languages. There might be  
some ObjC specific code
added inadvertently  though which should be moved out.

- Fariborz


>
> 	- Doug
>
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