Correctly importing uuid

[Jacek Caban]

Hi Anton,


On 2/16/18 7:35 AM, Anton Romanov wrote:
> Hi all,
>
> I'm working on dlls/wmp and I have added code that now requires GUID_NULL.
> Instead of duplicating its definition I was trying to add "uuid" to
> IMPORTS section of Makefile.
> When I do that I get get multiple definitions of various GUIDs.
> To fix that I have removed
> #include "initguid.h"
> from wmp_main.c . That fixes multiple definitions however this brings
> undefined references such as:
>
> wine/dlls/wmp/oleobj.c:255: undefined reference to `IID_IWMPCore'
> x86_64-pc-linux-gnu/bin/ld: oleobj.o: relocation R_386_GOTOFF against
> undefined hidden symbol `IID_IWMPCore' can not be used when making a
> shared object
>
> now.
> It is unclear to me what is the right way to fix this issue. Can
> someone shed some light on a proper way to do that?
> (I can solve that by duplicating GUID_NULL definition but I was said
> that its not needed)
>

There are two main ways of importing uuids. First one, more common, is 
to add uuid (or other similar library) to IMPORTS in Makefile, which 
imports uuid from a static lib. This is usually preferred. However, this 
does not work nice in wmp.dll case because IID_IWMPCore (and other WMP 
uuids) are not present in any such lib.

In such cases we need to use the second way. Note that uuids are usually 
defined using DEFINE_GUID in headers, see guiddef.h for the macro. It 
expands to |extern const GUID| unless DEFINE_GUID is defined. If it's 
defined, full declaration is included. In wmp_main.c we include 
initguid.h, which defines DEFINE_GUID macro. It means that we will have 
uuids declared for all headers included in wmp_main.c.

That said, if you need more uuids in wmp.dll, just include a file 
containing their declarations in wmp_main.c.

Thanks,
Jacek