[Mingw-w64-public] [PATCH] guiddef.h: Use __declspec(selectany) on GUID declarations.

[David G. <dav...@gm...>]

If __declspec(selectany) is not used on the prototype but later used on 
a definition, GCC seems to ignore it, and you can get 
multiple-definition errors at link time.

That situation can arise in code like Microsoft's usbview utility that 
has multiple translation units including the following headers:

#include <windows.h>
#include <initguid.h>
#include <winioctl.h>

When I have two files that include those header files in that order and 
I try to compile them with "i686-w64-mingw32-gcc main.c other.c -o 
test.exe", I get a bunch of errors like this:

/home/david/tmp/ccB3GiUW.o:other.c:(.rdata+0x0): multiple definition of 
`GUID_DEVINTERFACE_DISK'
/home/david/tmp/ccRH9Bjf.o:main.c:(.rdata+0x0): first defined here
/home/david/tmp/ccB3GiUW.o:other.c:(.rdata+0x10): multiple definition of 
`GUID_DEVINTERFACE_CDROM'
/home/david/tmp/ccRH9Bjf.o:main.c:(.rdata+0x10): first defined here

This patch fixes that by adding __declspec(selectany) to the GUID 
declarations.

Thanks!

--David Grayson