Simplify ALLOW_UNUSED_LOCAL to use (void)x directly instead of conditionally.

base/compiler_specific.h

Index: base/compiler_specific.h
diff --git a/base/compiler_specific.h b/base/compiler_specific.h
index 0f4c058b3be43963d76c23b0b3b8ec89fc8b3767..287e51184a3a902f3a495e284fc642a5b3192d88 100644
--- a/base/compiler_specific.h
+++ b/base/compiler_specific.h
@@ -71,15 +71,27 @@
 
 #endif  // COMPILER_MSVC
 
-
 // Annotate a variable indicating it's ok if the variable is not used.
 // (Typically used to silence a compiler warning when the assignment
 // is important for some other reason.)
 // Use like:
 //   int x = ...;
 //   ALLOW_UNUSED_LOCAL(x);
+//
+// The common-case implementation references |x| in such a way that it's never
+// evaluated.  Static analysis builds still see this as not referencing |x|, so
+// in such cases we reference it directly to make the compiler happy, at the
+// risk of unintended side effects.
+#if defined(__clang_analyzer__)
+
+#define ALLOW_UNUSED_LOCAL(x) (void)x
+
+#else  // !defined(__clang_analyzer__)
+
 #define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0

[Nico, 2017/04/25 15:48:52]

What was the problem with making this use `(void)x` again?

[Kevin Marshall, 2017/04/25 17:17:31]

When I asked pkasting (author of the original #define), he said the ternary
expression guarantees no side effects as a result of storing 'x'. I don't the
specifics about which types are affected.

 
+#endif  // defined(__clang_analyzer__)
+
 // Annotate a typedef or function indicating it's ok if it's not used.
 // Use like:
 //   typedef Foo Bar ALLOW_UNUSED_TYPE;