_ANONYMOUS_STRUCT (again)

[Christopher Faylor]

On Mon, Sep 10, 2001 at 02:48:16PM +1000, Danny Smith wrote:
>The last change to the anonymous struct in LARGE_INTEGER in winnt.h,
>doesn't make sense to me.

I must be missing something.

Reading windows.h, I'm having a hard time seeing how ANONYMOUS_STRUCT could
ever be undefined.

With my my cross gcc compiler, which is based on gcc 3.0.1, this code does 
not work:

#define _ANONYMOUS_STRUCT
#if _ANONYMOUS_STRUCT ||  defined(foo)
"foo"=1;
#endif

% i686-pc-cygwin-gcc tst.c -c
tst.c:2:23: operator 'EOL' has no left operand

With gcc 2.95.3, I get this (as expected):

% /cygwin/bin/i686-pc-cygwin-gcc tst.c -c
tst.c:2: parse error

If I change the file to this:

define _ANONYMOUS_STRUCT __extension__
#if _ANONYMOUS_STRUCT ||  defined(foo)
"foo"=1;
#endif

Then I get this for both 3.0.1 and 2.95.3:

% i686-pc-cygwin-gcc -c /tmp/tst.c
%

In other words, the compiler ignores line three of the file, which is
not the expected behavior.

>Sat Sep  1 10:40:37 2001  Christopher Faylor <cgf@cygnus.com>
>
>	* include/winnt.h: Use defined(_ANONYMOUS_STRUCT) to determine if
>	anonymous structs are available rather than just testing preprocessor
>	variable directly.
>
>
>
> _ANONYMOUS_STRUCT is always defined in windows.h, so the
>#if defined(_ANONYMOUS_STRUCT) conditional doesn't do anything.  
>If you compile this
>
>#define NONMAMELESSUNION
>#include <windows.h>
>
>with current CVS winnt.h, the _[U]LARGE_INTEGER structs throw pedantic
>warnings.
>
>If you don't like the #if _ANONYMOUS_STRUCT syntax (which doesn't
>cause any problems for me with 3.0.1 or with 2.95.3, as long as I
>include windows.h first), here is a macro guard that actually does
>something.

I don't like it for the above reasons.

I'm not wild about using something called NONAMELESSUNION to control
whether a nameless *structure* is defined but I guess it's ok.

cgf

>I've also picked up another nameless union that wasn't protected.
>
>Now, if we are really serious about pedantic warnings,we need to
>protect against all the non-ANSI bit-fields in w32api structs.
>
>Danny
>
>ChangeLog
>
>2001-09-10  Danny Smith  <dannysmith@users.sourceforge.net>
> 	* include/winnt.h (_[U]LARGE_INTEGER): Protect nameless struct with
>	!defined(NONAMELESSUNION), rather than defined(_ANONYMOUS_STRUCT).
>	(_REPARSE_DATA_BUFFER): Name union field DUMMYUNIONNAME.
>
>--- winnt.h.orig	Mon Sep 10 15:55:31 2001
>+++ winnt.h	Mon Sep 10 16:06:55 2001
>@@ -1705,7 +1705,7 @@ typedef union _LARGE_INTEGER {
>     DWORD LowPart;
>     LONG  HighPart;
>   } u;
>-#if defined(_ANONYMOUS_STRUCT) || defined(__cplusplus)
>+#if ! defined(NONAMELESSUNION) || defined(__cplusplus)
>   struct {
>     DWORD LowPart;
>     LONG  HighPart;
>@@ -1718,7 +1718,7 @@ typedef union _ULARGE_INTEGER {
>     DWORD LowPart;
>     DWORD HighPart;
>   } u;
>-#if defined(_ANONYMOUS_STRUCT) || defined(__cplusplus)
>+#if ! defined(NONAMELESSUNION) || defined(__cplusplus)
>   struct {
>     DWORD LowPart;
>     DWORD HighPart;
>@@ -2502,7 +2502,7 @@ typedef struct _REPARSE_DATA_BUFFER {
> 		struct {
> 			BYTE   DataBuffer[1];
> 		} GenericReparseBuffer;
>-	};
>+	} DUMMYUNIONNAME;
> } REPARSE_DATA_BUFFER, *PREPARSE_DATA_BUFFER;
> typedef struct _REPARSE_GUID_DATA_BUFFER {
> 	DWORD  ReparseTag;
>
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