Everyone gets a namespace {}.

src/core/Sk4px.h

 /*
  * Copyright 2015 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef Sk4px_DEFINED
 #define Sk4px_DEFINED
 
 #include "SkNx.h"
 #include "SkColor.h"
 
+// This file may be included multiple times by .cpp files with different flags, leading
+// to different definitions.  Usually that doesn't matter because it's all inlined, but
+// in Debug modes the compilers may not inline everything.  So wrap everything in an
+// anonymous namespace to give each includer their own silo of this code (or the linker
+// will probably pick one randomly for us, which is rarely correct).
+namespace {
+
 // 1, 2 or 4 SkPMColors, generally vectorized.
 class Sk4px : public Sk16b {
 public:
     Sk4px(SkAlpha a) : INHERITED(a) {} // Duplicate 16x: a    -> aaaa aaaa aaaa aaaa
     Sk4px(SkPMColor);                  // Duplicate 4x:  argb -> argb argb argb argb
     Sk4px(const Sk16b& v) : INHERITED(v) {}
 
     Sk4px alphas() const;  // ARGB argb XYZW xyzw -> AAAA aaaa XXXX xxxx
 
     // Mask away color or alpha lanes.
@@ skipping 140 matching lines @@
                 fn(Load1(dst), Load1(src), alpha).store1(dst);
             }
             break;
         }
     }
 
 private:
     typedef Sk16b INHERITED;
 };
 
+}  // namespace
+
 #ifdef SKNX_NO_SIMD
     #include "../opts/Sk4px_none.h"
 #else
     #if SK_CPU_SSE_LEVEL >= SK_CPU_SSE_LEVEL_SSE2
         #include "../opts/Sk4px_SSE2.h"
     #elif defined(SK_ARM_HAS_NEON)
         #include "../opts/Sk4px_NEON.h"
     #else
         #include "../opts/Sk4px_none.h"
     #endif
 #endif
 
 #endif//Sk4px_DEFINED