dxsdk/SAL: activate compat shim on GCC/MinGW and add SAL 1 bytecount family

The existing dxsdk_sal_compat.h was gated on `_MSC_VER < 1700`, which
made the entire shim body invisible to GCC/MinGW toolchains. This
worked because mingw-w64's <sal.h> historically provided the SAL
macros the bundled DX headers reference -- but not all mingw-w64
releases are complete. MSYS2's current mingw-w64 sal.h omits the
legacy SAL 1 form `_Inout_opt_bytecount_`, which the bundled d3d11.h
references, so the MXE/MinGW cross-build of gfx/common/dx_guids.c
fails to parse d3d11.h.

Fix the gate and extend macro coverage:

 * Replace the `_MSC_VER < 1700` gate with a portable form that pulls
   in <sal.h> via `__has_include` on non-MSVC toolchains. The shim
   body then runs on every toolchain, and the per-macro `#ifndef`
   guards prevent redefinition wherever the toolchain already
   provides the macro. Net effect on MSVC 2012+ and on complete
   mingw-w64 releases: no-op. On MSVC 2003-2010 and incomplete
   mingw-w64 releases: missing macros are stubbed.

 * Add the SAL 1 underscore-prefix bytecount/ecount family
   (`_In_bytecount_[_opt_]`, `_Out_bytecount_[_opt_]`,
   `_Inout_bytecount_[_opt_]`, `_Inout_opt_bytecount_`, and the
   four `_ecount_[_opt_]` equivalents). `_Inout_opt_bytecount_`
   is the one actually observed in the MXE/MSYS2 build log; the
   siblings are added together because they commonly surface in
   the same parse cascade once any one of them fails.

 * Update the file comment to document MinGW-w64 coverage and the
   no-op behavior on MSVC 2012+.

Also propagate `#include "dxsdk_sal_compat.h"` to the bundled DX
headers that didn't already have it:

 * gfx/include/dxsdk/d3d10.h, d3d10_1.h, d3d11.h, d3d11shader.h,
   d3d12.h, d3d12shader.h, d3dcompiler.h: add the shim include at
   line 1, ahead of the MIDL-generated preamble.

The dxgi1_*.h, d3dcommon.h, and dxgi.h headers already got this
in an earlier commit; d3d8.h and d3d9.h are not bundled.

Downstream effect:
 * MXE/MSYS2 mingw-w64 cross-build: resolves the
   `unknown type name '_Inout_opt_bytecount_'` error in
   gfx/common/dx_guids.c's transitive include of d3d11.h.
 * MSVC 2003-2010: unchanged (every new stub is #ifndef-guarded,
   and the SAL 2 additions from the prior dxgi patch remain intact).
 * MSVC 2012+: unchanged (<sal.h> provides everything, stubs no-op).

Author: LibretroAdmin

gfx/include/dxsdk/d3d10.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 /*-------------------------------------------------------------------------------------
  *
  * Copyright (c) Microsoft Corporation

gfx/include/dxsdk/d3d10_1.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 /*-------------------------------------------------------------------------------------
  *
  * Copyright (c) Microsoft Corporation

gfx/include/dxsdk/d3d11.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 /*-------------------------------------------------------------------------------------
  *
  * Copyright (c) Microsoft Corporation

gfx/include/dxsdk/d3d11shader.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 //////////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (c) Microsoft Corporation.  All rights reserved.

gfx/include/dxsdk/d3d12.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 /*-------------------------------------------------------------------------------------
  *
  * Copyright (c) Microsoft Corporation

gfx/include/dxsdk/d3d12shader.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 //////////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (c) Microsoft Corporation.  All rights reserved.

gfx/include/dxsdk/d3dcompiler.h

@@ -1,3 +1,6 @@
+/* SAL compatibility shim for legacy MSVC and some MinGW-w64 */
+#include "dxsdk_sal_compat.h"
+
 //////////////////////////////////////////////////////////////////////////////
 //
 //  Copyright (c) Microsoft Corporation.  All rights reserved.

gfx/include/dxsdk/dxsdk_sal_compat.h

@@ -14,15 +14,21 @@
  *     the buffer-size, COM-outptr, and wrapper families. We fill
  *     in the gaps.
  *   * MSVC 2012+ (_MSC_VER >= 1700): full SAL 2 in <sal.h>. The
- *     whole shim is skipped.
+ *     shim's <sal.h> include picks it up; every stub below is
+ *     guarded with #ifndef, so the shim adds nothing.
+ *   * MinGW-w64 (GCC, Clang): ships its own <sal.h>. Coverage has
+ *     varied across releases; some are missing legacy SAL 1
+ *     "bytecount"/"ecount" forms like _Inout_opt_bytecount_. The
+ *     shim fills in any gaps via the same #ifndef-guarded stubs.
  *
  * Usage: #include "dxsdk_sal_compat.h" at the top of any bundled
  * DirectX header (d3dcommon.h, d3d11shader.h, d3dcompiler.h, etc.)
  * that uses SAL annotations. Place it immediately after the include
  * guard and before any declarations.
  *
  * Every macro is wrapped in #ifndef so we only fill in what the
- * toolchain is missing, avoiding C4005 redefinition warnings.
+ * toolchain is missing, avoiding C4005 redefinition warnings on
+ * MSVC and -Wmacro-redefined on Clang.
  *
  * The macros expand to nothing (or to a pass-through for the "wrapper"
  * forms like _Always_(x) / _When_(c,x)) so that declarations using
@@ -35,15 +41,22 @@
 #ifndef DXSDK_SAL_COMPAT_H
 #define DXSDK_SAL_COMPAT_H
 
-/* Only kick in on pre-VS2012 MSVC, which lacks full SAL 2.
- * _MSC_VER 1700 == VS2012, first to ship full SAL 2 broadly. */
-#if defined(_MSC_VER) && _MSC_VER < 1700
-
-/* <sal.h> first appeared in MSVC 2005 (_MSC_VER 1400).
- * MSVC 2003 and earlier have no sal.h, so don't try to include it. */
-#if _MSC_VER >= 1400
+/* The shim activates on any toolchain whose SAL header set is
+ * incomplete -- which in practice means pre-VS2012 MSVC *and* some
+ * MinGW-w64 releases whose <sal.h> omits legacy SAL 1 forms like
+ * _Inout_opt_bytecount_. Per-macro #ifndef guards below make this a
+ * no-op on toolchains that already have proper definitions, so
+ * activating unconditionally is safe.
+ *
+ * We still try to include <sal.h> where it exists, so that the
+ * #ifndef guards pick up whatever the toolchain does provide. */
+#if defined(_MSC_VER) && _MSC_VER >= 1400
+#include <sal.h>
+#elif defined(__has_include)
+#if __has_include(<sal.h>)
 #include <sal.h>
 #endif
+#endif
 
 /* --- SAL 1 forms (double-underscore) --------------------------------- *
  * Present in MSVC 2005+, absent in MSVC 2003. Stub them unconditionally
@@ -126,6 +139,50 @@
 #ifndef __field_bcount
 #define __field_bcount(s)
 #endif
+
+/* SAL 1 underscore-prefix bytecount/ecount family.
+ * Some mingw-w64 releases of <sal.h> omit these. MSVC 2005-2010 may
+ * also not define all of them depending on SP level. */
+#ifndef _In_bytecount_
+#define _In_bytecount_(s)
+#endif
+#ifndef _In_bytecount_opt_
+#define _In_bytecount_opt_(s)
+#endif
+#ifndef _Out_bytecount_
+#define _Out_bytecount_(s)
+#endif
+#ifndef _Out_bytecount_opt_
+#define _Out_bytecount_opt_(s)
+#endif
+#ifndef _Inout_bytecount_
+#define _Inout_bytecount_(s)
+#endif
+#ifndef _Inout_bytecount_opt_
+#define _Inout_bytecount_opt_(s)
+#endif
+#ifndef _Inout_opt_bytecount_
+#define _Inout_opt_bytecount_(s)
+#endif
+#ifndef _In_ecount_
+#define _In_ecount_(s)
+#endif
+#ifndef _In_ecount_opt_
+#define _In_ecount_opt_(s)
+#endif
+#ifndef _Out_ecount_
+#define _Out_ecount_(s)
+#endif
+#ifndef _Out_ecount_opt_
+#define _Out_ecount_opt_(s)
+#endif
+#ifndef _Inout_ecount_
+#define _Inout_ecount_(s)
+#endif
+#ifndef _Inout_ecount_opt_
+#define _Inout_ecount_opt_(s)
+#endif
+
 #ifndef __success
 #define __success(c)
 #endif
@@ -336,6 +393,4 @@
 #define _Analysis_assume_(c)
 #endif
 
-#endif /* _MSC_VER < 1700 */
-
 #endif /* DXSDK_SAL_COMPAT_H */