Namespace and extern "C" gives problems with forward struct declarations

[DimitryAndric]

Bugzilla Link	9162
Resolution	FIXED
Resolved on	Oct 09, 2011 17:58
Version	trunk
OS	All
CC	@DougGregor,@pwo

Extended Description

Clang has a problem compiling the gstreamer backend for KDE's phonon
library. I encountered this issue with trunk r125004. The reduced C++
code goes like this:

namespace Gstreamer {
extern "C" {
typedef struct _ArtsSink ArtsSink;
struct _ArtsSink {
int sink;
};
}
int arts_sink_get_type()
{
return sizeof(ArtsSink);
}
}

Compiling this with clang++ gives:

fwddecl.cpp:10:12: error: invalid application of 'sizeof' to an incomplete type 'ArtsSink' (aka 'Gstreamer::_ArtsSink')
return sizeof(ArtsSink);
^ ~~~~~~~~~~
fwddecl.cpp:3:20: note: forward declaration of 'Gstreamer::_ArtsSink'
typedef struct _ArtsSink ArtsSink;
^
1 error generated.

Granted, it is a bit weird how the KDE guys forward declare the
_ArtsSink struct, but as far as I can see, it should still compile.

I tried this fragment with g++ 4.2.1 (FreeBSD base system compiler), g++
4.5.3, and Coumeau 4.3.10.1, and they all accept it without any
complaint.

Note: the error goes away when you eliminate either the namespace or the
'extern "C"' block. Both are required to produce the error.

[DougGregor]

Fixed in Clang r141521.