[cfe-commits] [PATCH] Warn on non-compatible returns from extern "C" functions

[Aaron Ballman]

On Mon, Feb 6, 2012 at 4:47 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
> On Mon, Feb 6, 2012 at 2:40 PM, Aaron Ballman <aaron at aaronballman.com> wrote:
>> On Mon, Feb 6, 2012 at 4:33 PM, Eli Friedman <eli.friedman at gmail.com> wrote:
>>> On Sun, Feb 5, 2012 at 9:31 AM, Aaron Ballman <aaron at aaronballman.com> wrote:
>>>> MSVC will warn the user when a declared return type of an extern "C"
>>>> function is not C-compatible
>>>> (http://msdn.microsoft.com/en-us/library/1e02627y(v=vs.100).aspx).
>>>> This patch adds the same style of warning to clang, under the
>>>> -Wreturn-type group, with test cases.
>>>>
>>>> Is there a better way for me to check whether a type is "C compatible?"
>>>
>>> CXXRecordDecl::isCLike was added recently... not sure if it's what you want.
>>
>> Thanks, I'll check it out.
>
> Thinking about it a bit more, isPOD is probably closer to what you
> want... since you're actually worried about whether we guarantee C
> compatibility, not whether the struct could be copy-pasted into a C
> program.

On reflection, I think you're right.  I stuck with isPOD instead of isCLike.

>>> "UDT" is not a term we use anywhere in clang; please don't use it here.
>>
>> Suggestions on alternative wording?
>
> You could just expand out its definition.  MSVC's warning appears to
> be much more aggressive than what you are implementing here.

I've changed the wording to be:

%0 has C-linkage specified, but returns user-defined type %1 which is
incompatible with C

So the only changes to this patch are the test cases and the wording
for the warning itself.

~Aaron
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