fix crash with FOLDERID_LocalAppDataLow not found

[asinbow]

The macro DEFINE_KNOWN_FOLDER was copied from <KnownFolder.h>, it will link FOLDERID_LocalAppDataLow to an external dll.
but for some system(to me, Windows 7, Chinese Edition), the symbol can't be found at runtime, so FOLDERID_LocalAppDataLow becomes GUID_NULL, and at line 52, it will fail with crash.

Really strange.

Let's inspect <KnownFolder.h> again, there are two styles of DEFINE_KNOWN_FOLDER:

#ifdef INITGUID
#define DEFINE_KNOWN_FOLDER(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) \
        EXTERN_C const GUID DECLSPEC_SELECTANY name \
                = { l, w1, w2, { b1, b2,  b3,  b4,  b5,  b6,  b7,  b8 } }
#else
#define DEFINE_KNOWN_FOLDER(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) \
        EXTERN_C const GUID name
#endif // INITGUID

Shall we use the first one without extern?

[asinbow]

Let's rethink about this code:

1. at line 52, getKnownFolderPath could fail, make pszPath NULL. Better to check HRESULT to avoid crash.
2. DEFINE_KNOWN_FOLDER can be found <KnownFolder.h>, why redefine it? Maybe for compiler compatibility.
3. where to release HMODULE library?

Thank you for pay attention.

[taxilian]

Interesting. I'll have to make sure this still works on the english/russian version, but assuming it works on mine as well as the other one did I'll accept this.

[asinbow]

These days I compiled my project on VS2010, found a 'not found' link error, just because the EXTERN_C.
Maybe we should define a new macro all by ourselves,

#define FB_DEFINE_KNOWN_FOLDER(name, l, w1, w2, b1, b2, b3, b4, b5, b6, b7, b8) \
        const GUID DECLSPEC_SELECTANY name \
                = { l, w1, w2, { b1, b2,  b3,  b4,  b5,  b6,  b7,  b8 } }

Well, I do not know whether it would work in other cases, but the issue FOLDERID_LocalAppDataLow links to GUID_NULL at runtime does exists where using 'EXTERN_C'.

Thank you for paying attention.