[llvm-commits] [PATCH] Suppress "user-defined return type in extern C" warning under Clang

[Aaron Ballman]

On Tue, Feb 14, 2012 at 2:50 PM, Matt Johnson <johnso87 at illinois.edu> wrote:
> On 02/14/2012 02:42 PM, Aaron Ballman wrote:
>>
>> On Tue, Feb 14, 2012 at 2:28 PM, David Blaikie<dblaikie at gmail.com>  wrote:
>>>
>>> [+aaron who added this warning&  was already looking into the fix for
>>> LLVM]
>>>
>>>
>>> Perhaps you've got the right fix - but at least Aaron won't keep
>>> working on it redundantly. It looks reasonable to me.
>>
>> The patch looks like it will work the same for clang as it does for
>> MSVC, which is good.  But I'm a bit concerned as to why we have an
>> extern "C" function that returns a type that can't be represented in
>> C.  Is that the problem we should be solving instead?
>
> My understanding is that we're declaring these functions as 'extern "C"' not
> to actually call them from C code, but just to avoid mangling.  The VS2010
> docs (http://msdn.microsoft.com/en-us/library/1e02627y.aspx) state that if
> the definition and all calls are *actually* C++ code, doing this is legal.
>  I'm far from an authority on the matter, but it sounds reasonable.

That certainly is true, and is reasonable.  :-)  I'm just trying to
figure out the "why" part of it.  Why do we not want mangled names in
this situation?  If it makes sense, which I'm betting it does, then
your fix is great.  If we want non-mangled names for some sort of
interoperability, then I think we may want to do something other than
suppress the warning.

~Aaron