--- a/gfx/skia/skia/include/config/SkUserConfig.h
+++ b/gfx/skia/skia/include/config/SkUserConfig.h
@@ -153,17 +153,17 @@
 
 #define SK_RASTERIZE_EVEN_ROUNDING
 
 #define SK_DISABLE_SCREENSPACE_TESS_AA_PATH_RENDERER
 
 #define SK_DISABLE_SLOW_DEBUG_VALIDATION 1
 
 #ifndef MOZ_IMPLICIT
-#  ifdef MOZ_CLANG_PLUGIN
+#  if defined(MOZ_CLANG_PLUGIN) && defined(__clang__)
 #    define MOZ_IMPLICIT __attribute__((annotate("moz_implicit")))
 #  else
 #    define MOZ_IMPLICIT
 #  endif
 #endif
 
 #define MOZ_SKIA
 

--- a/mfbt/Attributes.h
+++ b/mfbt/Attributes.h
@@ -570,17 +570,17 @@
  *   within the calling block using an explicit `return` statement.
  *   Only calls to Constructors, references to local and member variables,
  *   and calls to functions or methods marked as MOZ_MAY_CALL_AFTER_MUST_RETURN
  *   may be made after the MUST_RETURN_FROM_CALLER call.
  * MOZ_MAY_CALL_AFTER_MUST_RETURN: Applies to function or method declarations.
  *   Calls to these methods may be made in functions after calls a
  *   MOZ_MUST_RETURN_FROM_CALLER function or method.
  */
-#ifdef MOZ_CLANG_PLUGIN
+#if defined(MOZ_CLANG_PLUGIN) && defined(__clang__)
 #  define MOZ_MUST_OVERRIDE __attribute__((annotate("moz_must_override")))
 #  define MOZ_STACK_CLASS __attribute__((annotate("moz_stack_class")))
 #  define MOZ_NONHEAP_CLASS __attribute__((annotate("moz_nonheap_class")))
 #  define MOZ_HEAP_CLASS __attribute__((annotate("moz_heap_class")))
 #  define MOZ_NON_TEMPORARY_CLASS __attribute__((annotate("moz_non_temporary_class")))
 #  define MOZ_TRIVIAL_CTOR_DTOR __attribute__((annotate("moz_trivial_ctor_dtor")))
 #  ifdef DEBUG
      /* in debug builds, these classes do have non-trivial constructors. */