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..7e77296b93c0ff4b8866d148b1903d6717ae4f85 100644
--- a/base/compiler_specific.h
+++ b/base/compiler_specific.h
@@ -78,8 +78,19 @@
 // Use like:
 //   int x = ...;
 //   ALLOW_UNUSED_LOCAL(x);
+#if defined(__clang_analyzer__)
+
+// Voidify 'x' on codepath-sensitive static analyzer builds, potentially
+// producing side effects.
+#define ALLOW_UNUSED_LOCAL(x) (void)x
+
+#else  // !defined(__clang_analyzer__)
+
+// Voidify 'x' without side effects.
 #define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
 
+#endif  // defined(__clang_analyzer__)

[Peter Kasting, 2017/04/24 21:59:25]

Nit: I think this would be easier to read with comment above the #if:

// 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
#define ALLOW_UNUSED_LOCAL(x) false ? (void)x : (void)0
#endif

[Kevin M, 2017/04/24 22:37:39]

Yes, that's an improvement. Thanks, done.

+
 // Annotate a typedef or function indicating it's ok if it's not used.
 // Use like:
 //   typedef Foo Bar ALLOW_UNUSED_TYPE;