[PATCH 07/12] win32: use compiler option instead of attribute gcc_struct

[Pierrick Bouvier <pierrick.bouvier@linaro.org>]

This attribute is not recognized by clang, but the associated option is.

Signed-off-by: Pierrick Bouvier <pierrick.bouvier@linaro.org>
---
 meson.build                               | 8 ++++----
 include/qemu/compiler.h                   | 7 +------
 subprojects/libvhost-user/libvhost-user.h | 6 +-----
 3 files changed, 6 insertions(+), 15 deletions(-)

diff --git a/meson.build b/meson.build
index d8af08299e0..d0d5dbe1479 100644
--- a/meson.build
+++ b/meson.build
@@ -330,10 +330,10 @@ elif host_os == 'sunos'
 elif host_os == 'haiku'
   qemu_common_flags += ['-DB_USE_POSITIVE_POSIX_ERRORS', '-D_BSD_SOURCE', '-fPIC']
 elif host_os == 'windows'
-  if not compiler.compiles('struct x { int y; } __attribute__((gcc_struct));',
-                           args: '-Werror')
-    error('Your compiler does not support __attribute__((gcc_struct)) - please use GCC instead of Clang')
-  endif
+  # https://gcc.gnu.org/onlinedocs/gcc/x86-Type-Attributes.html
+  # We use this compilation option instead of relying on gcc_struct attribute
+  # because clang does not support it (but supports the option).
+  qemu_common_flags += ['-mno-ms-bitfields']
 endif
 
 # Choose instruction set (currently x86-only)
diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index c06954ccb41..d904408e5ed 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -22,12 +22,7 @@
 #define QEMU_EXTERN_C extern
 #endif
 
-#if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
-# define QEMU_PACKED __attribute__((gcc_struct, packed))
-#else
-# define QEMU_PACKED __attribute__((packed))
-#endif
-
+#define QEMU_PACKED __attribute__((packed))
 #define QEMU_ALIGNED(X) __attribute__((aligned(X)))
 
 #ifndef glue
diff --git a/subprojects/libvhost-user/libvhost-user.h b/subprojects/libvhost-user/libvhost-user.h
index deb40e77b3f..2ffc58c11b1 100644
--- a/subprojects/libvhost-user/libvhost-user.h
+++ b/subprojects/libvhost-user/libvhost-user.h
@@ -186,11 +186,7 @@ typedef struct VhostUserShared {
     unsigned char uuid[UUID_LEN];
 } VhostUserShared;
 
-#if defined(_WIN32) && (defined(__x86_64__) || defined(__i386__))
-# define VU_PACKED __attribute__((gcc_struct, packed))
-#else
-# define VU_PACKED __attribute__((packed))
-#endif
+#define VU_PACKED __attribute__((packed))
 
 typedef struct VhostUserMsg {
     int request;
-- 
2.39.5