Fix attribute use on Clang

folly/CPortability.h

@@ -122,10 +122,17 @@
 
 #if FOLLY_SANITIZE
 /**
- * GCC 8.2.0 and Clang 6.0 both support the no_sanitize attribute, however,
- * GCC 7.3.0 does not. Check for alternative attributes if no_sanitize is not
- * available.
+ * GCC 8.2.0 asupports the no_sanitize attribute, however, GCC 7.3.0 does not.
+ * Check for alternative attributes if no_sanitize is not available. For Clang,
+ * we should use the __no_sanitize__ attribute.
  */
+#if defined(__clang__)
+#if __has_attribute(__no_sanitize__)
+#define FOLLY_DISABLE_UNDEFINED_BEHAVIOR_SANITIZER \
+  __attribute__((__no_sanitize__("address")))
+#endif // __has_attribute(__no_sanitize__)
+#elif defined(__GNUC__)
+
 #if defined(__has_cpp_attribute)
 
 #if __has_cpp_attribute(no_sanitize)
@@ -148,6 +155,7 @@
 #error __has_cpp_attribute was not found, cannot determine which attributes to\
        use.
 #endif // defined(__has_cpp_attribute)
+#endif
 #else // FOLLY_SANITIZE
 #define FOLLY_DISABLE_UNDEFINED_BEHAVIOR_SANITIZER
 #define FOLLY_DISABLE_NONNULL_SANITIZER