[cfe-dev] CLang compiling windows.h from the Windows SDK

[Douglas Gregor]

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On Aug 9, 2010, at 7:19 PM, Francois Pichet <pichet2000 at gmail.com> wrote:

> You are right. MSVC doesn't allow typedef redefinition after all.
> Here is a code simplification of what is happening in windows.h
> 
> struct A {
>    char a;
>    char b;
> };
> 
> typedef int foo[1];
> typedef int foo[(long)&(((A *)0)->b)];

This looks like an offsetof implementation. We're probably not treating it as a constant expression (but that's another guess), since C/C++  doesn't consider it to be a constant expression (GCC and VC++ have extensions in this area). 

> clang will flag the second typedef as a redefintion. msvc and gcc don't.
> 
> 
> 
> On Sun, Aug 8, 2010 at 4:07 PM, Douglas Gregor <dgregor at apple.com> wrote:
> 
>>> 
>>> In C mode there are only 2 kinds of error:
>>> 1- MSVC allows typedef redefinition with a different type, CLang doesn't.
>> 
>> What types are involved? This may be a symptom of a different incompatibility  in the type system.
>>