Using "defined" in macro causes undefined behavior.

include/v8config.h

 // Copyright 2013 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8CONFIG_H_
 #define V8CONFIG_H_
 
+// clang-format off
+
 // Platform headers for feature detection below.
 #if defined(__ANDROID__)
 # include <sys/cdefs.h>
 #elif defined(__APPLE__)
 # include <TargetConditionals.h>
 #elif defined(__linux__)
 # include <features.h>
 #endif
 
 
@@ skipping 205 matching lines @@
 # define V8_HAS_BUILTIN_SADD_OVERFLOW (__has_builtin(__builtin_sadd_overflow))
 # define V8_HAS_BUILTIN_SSUB_OVERFLOW (__has_builtin(__builtin_ssub_overflow))
 # define V8_HAS_BUILTIN_UADD_OVERFLOW (__has_builtin(__builtin_uadd_overflow))
 
 # define V8_HAS_CXX11_ALIGNAS (__has_feature(cxx_alignas))
 # define V8_HAS_CXX11_STATIC_ASSERT (__has_feature(cxx_static_assert))
 
 #elif defined(__GNUC__)
 
 # define V8_CC_GNU 1
-// Intel C++ also masquerades as GCC 3.2.0
-# define V8_CC_INTEL (defined(__INTEL_COMPILER))
-# define V8_CC_MINGW32 (defined(__MINGW32__))
-# define V8_CC_MINGW64 (defined(__MINGW64__))
+# if defined(__INTEL_COMPILER)  // Intel C++ also masquerades as GCC 3.2.0
+#  define V8_CC_INTEL 1
+# endif
+# if defined(__MINGW32__)
+#  define V8_CC_MINGW32 1
+# endif
+# if defined(__MINGW64__)
+#  define V8_CC_MINGW64 1
+# endif
 # define V8_CC_MINGW (V8_CC_MINGW32 || V8_CC_MINGW64)
 
 # define V8_HAS___ALIGNOF__ (V8_GNUC_PREREQ(4, 3, 0))
 
 # define V8_HAS_ATTRIBUTE_ALIGNED (V8_GNUC_PREREQ(2, 95, 0))
 // always_inline is available in gcc 4.0 but not very reliable until 4.4.
 // Works around "sorry, unimplemented: inlining failed" build errors with
 // older compilers.
 # define V8_HAS_ATTRIBUTE_ALWAYS_INLINE (V8_GNUC_PREREQ(4, 4, 0))
 # define V8_HAS_ATTRIBUTE_DEPRECATED (V8_GNUC_PREREQ(3, 4, 0))
@@ skipping 158 matching lines @@
 
 // Annotate a function indicating the caller must examine the return value.
 // Use like:
 //   int foo() WARN_UNUSED_RESULT;
 #if V8_HAS_ATTRIBUTE_WARN_UNUSED_RESULT
 #define V8_WARN_UNUSED_RESULT __attribute__((warn_unused_result))
 #else
 #define V8_WARN_UNUSED_RESULT /* NOT SUPPORTED */
 #endif
 
+// clang-format on
+
 #endif  // V8CONFIG_H_