[XEN PATCH 1/3] x86/emul: define pseudo keyword fallthrough

[Federico Serafini <federico.serafini@xxxxxxxxxxx>]

The pseudo keyword fallthrough shall be used to make explicit the
fallthrough intention at the end of a case statement (doing this
through comments is deprecated).

Signed-off-by: Federico Serafini <federico.serafini@xxxxxxxxxxx>
---
 xen/arch/x86/x86_emulate/x86_emulate.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/xen/arch/x86/x86_emulate/x86_emulate.h 
b/xen/arch/x86/x86_emulate/x86_emulate.h
index d75658eba0..f49b1e0dd8 100644
--- a/xen/arch/x86/x86_emulate/x86_emulate.h
+++ b/xen/arch/x86/x86_emulate/x86_emulate.h
@@ -23,6 +23,16 @@
 # error Unknown compilation width
 #endif
 
+/*
+ * Pseudo keyword 'fallthrough' to make explicit the fallthrough intention at
+ * the end of a case statement.
+ */
+#if (!defined(__clang__) && (__GNUC__ >= 7))
+# define fallthrough        __attribute__((__fallthrough__))
+#else
+# define fallthrough        do {} while (0)  /* fallthrough */
+#endif
+
 struct x86_emulate_ctxt;
 
 /*
-- 
2.43.0