add padding member to SpiceMsgEmpty

Empty structures are undefined in C, gcc handles them without issue
assigning a size of 0. However MSVC++ generates a hard error (C2015)
this allows messages.h to be included in c files compiled by MSVC++.

Signed-off-by: Aric Stewart <aric@codeweavers.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/common/messages.h b/common/messages.h
index 58e8bee..106a8d3 100644
--- a/common/messages.h
+++ b/common/messages.h
@@ -52,6 +52,7 @@ typedef struct SpiceMsgData {
 } SpiceMsgData;
 
 typedef struct SpiceMsgEmpty {
+    uint8_t padding;
 } SpiceMsgEmpty;
 
 typedef struct SpiceMsgInputsInit {