[PATCH v4 03/16] qemu/compiler.h: Add optimize_away

[Richard Henderson]

Use this as a compile-time assert that a particular
code path is not reachable.

Signed-off-by: Richard Henderson <address@hidden>
---
 include/qemu/compiler.h | 15 +++++++++++++++
 1 file changed, 15 insertions(+)

diff --git a/include/qemu/compiler.h b/include/qemu/compiler.h
index 20780e722d..6604ccea92 100644
--- a/include/qemu/compiler.h
+++ b/include/qemu/compiler.h
@@ -221,4 +221,19 @@
 #define QEMU_GENERIC9(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC8(x, 
__VA_ARGS__))
 #define QEMU_GENERIC10(x, a0, ...) QEMU_GENERIC_IF(x, a0, QEMU_GENERIC9(x, 
__VA_ARGS__))
 
+/**
+ * optimize_away()
+ *
+ * The compiler, during optimization, is expected to prove that a call
+ * to this function cannot be reached and remove it.  If the compiler
+ * supports QEMU_ERROR, this will be reported at compile time; otherwise
+ * this will be reported at link time, due to the missing symbol.
+ */
+#ifdef __OPTIMIZE__
+extern void QEMU_NORETURN QEMU_ERROR("code path is reachable")
+    optimize_away(void);
+#else
+#define optimize_away()  g_assert_not_reached()
+#endif
+
 #endif /* COMPILER_H */
-- 
2.17.1