Re: [boost] [winapi] Problem with the latest clang on Windows

Subject: Re: [boost] [winapi] Problem with the latest clang on Windows
From: Edward Diener (eldiener_at_[hidden])
Date: 2015-05-31 21:31:37

On 5/31/2015 8:44 PM, Niall Douglas wrote:
> On 31 May 2015 at 20:07, Edward Diener wrote:
>
>> It seems like the fix for clang is to leave out the
>> __declspec(dllimport) portion of all these Boost winapi calls while
>> leaving it in for everybody else. I am discussing this on the clang
>> developers mailing list but it seems like they are pretty adamant that
>> if they see __attribute__((dllimport)) in from of a function declaration
>> and do not see it in front of another function declaration, despite the
>> rest of the signatire being the same, the two declarations are not the
>> same function being declared and therefore an error because of ODR.
>
> Oddly enough this topic came up at C++ Now when I was chatting with
> Chandler.
>
> They are immovable on clang being standards conformant in mingw mode.
> That means API declarations must match. Else it's a bug, and it will
> be errored out. Just because MSVC uses sloppy declspec doesn't mean
> it's valid C++. They will not back down, or change their mind on
> this, period.

Evidently from my OP it is gcc being sloppy.

>
> Switching clang into msvc mode makes everything just work.

Clang in MSVC mode means you're dealing with a compiler trying to 
emulate a broken preprocessor. No thanks ! I already had this discussion 
on the clang mailing lists and since they are adamant that they must 
attempt to emulate the VC++ preprocessor bugs in all situations I will 
not use that mode. I suggested to them a system by which they could 
emulate the broken VC++ preprocessor for VC++ headers which need it and 
otherwise support a C++ standard compliant preprocessor everywhere else, 
but they did not want to consider it.

So it doesn't make everything just work. In fact it may break any Boost 
library which uses Boost PP. And that's not a problem which Boost PP is 
going to try to solve.

Boost build also doesn't have built-in support for clang in VC++ mode on 
Windows but works fine with clang in gcc mode on Windows.

>
> For reference. Boost.Thread no longer compiles at all on clang in
> mingw mode for the same reason, but nearly gets there with clang in
> msvc mode. I suspect plenty more libraries are similar. At some point
> we'll need to go fix up all our code.

If we fix up Boost win32 we might be OK. That was the gist of my OP.