Re: [MinGW-dvlpr] W32API header question

[Luke D. <cod...@ho...>]

----- Original Message -----
From: "Jerry van Dijk" <jv...@at...>
To: <min...@li...>
Sent: Saturday, January 18, 2003 1:58 AM
Subject: [MinGW-dvlpr] W32API header question


> I am looking closely at the W32API headers for conversion
> into Ada. I ran into the following (from winnt.h):
>
> typedef union _LARGE_INTEGER {
>   struct {
>     DWORD LowPart;
>     LONG  HighPart;
>   } u;
> #if ! defined(NONAMELESSUNION) || defined(__cplusplus)
>   _ANONYMOUS_STRUCT struct {
>     DWORD LowPart;
>     LONG  HighPart;
>   };
> #endif /* NONAMELESSUNION */
>   LONGLONG QuadPart;
> } LARGE_INTEGER, *PLARGE_INTEGER;
>
> What is the purpose of the _ANONYMOUS_STUCT (or UNION)

If you have a LARGE_INTEGER variable "foo", it allows you to use a shorthand
"foo.LowPart" instead of "foo.u.LowPart". This is necessary because MSDN
says it is.

> and
> why is it only defined for c++ ?

Note the "||". It is defined for both C++, and for C unless NONAMELESSUNION
is defined. Anonymous unions and structs are apparently always supported in
C++, but I think some older versions of GCC didn't support them so the
headers check for NONAMELESSUNION. If you are talking about just the
_ANONYMOUS_STRUCT symbol itself, see windef.h and the GCC documentation for
__extension__: it is necessary to suppress warnings when compiling
with -pedantic.

>
> --  Jerry van Dijk   | email: jd...@ac...
> --  Leiden, Holland  | web:   users.ncrvnet.nl/gmvdijk

Luke