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

[Douglas Gregor]

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.

	- Doug