Clean up some assertion code in WebKit.

third_party/WebKit/Source/wtf/Assertions.h

 /*
  * Copyright (C) 2003, 2006, 2007 Apple Inc.  All rights reserved.
  * Copyright (C) 2013 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
@@ skipping 168 matching lines @@
 //  They are deprecated. We should use:
 //    - DCHECK() for ASSERT()
 //    - NOTREACHED() for ASSERT_NOT_REACHED()
 //    - DCHECK() and ALLOW_UNUSED_LOCAL() for ASSERT_UNUSED().
 #if OS(WIN)
 // FIXME: Change to use something other than ASSERT to avoid this conflict with
 // the underlying platform.
 #undef ASSERT
 #endif
 
+#define DCHECK_AT(assertion, file, line) LAZY_STREAM(logging::LogMessage(file, line, #assertion).stream(), DCHECK_IS_ON() ? !(assertion) : false)

[Stephen White, 2016/08/27 23:20:21]

Wouldn't this be clearer as

#if DCHECK_IS_ON()
#define DCHECK_AT(assertion, file, line) LAZY_STREAM(logging::LogMessage(file,
line, #assertion).stream(), !(assertion))
#else
#define DCHECK_AT(assertion, file, line) EAT_STREAM_PARAMETERS
#endif

i.e., same as before, but putting it behind #if DHECK_IS_ON() instead of #if
ENABLE(ASSERT) ? Or am I missing something?

[Wez, 2016/08/28 01:11:36]

The definition of DCHECK is specifically designed to ensure that |condition|
(aka |assertion| in this version) is referenced even if DCHECK is off, so the
compiler won't complain about unused variables that the condition would
otherwise reference. We then rely on the compiler optimizing the condition out
when it sees that DCHECK_IS_ON() is always true.

+
 #if ENABLE(ASSERT)
 
 #define ASSERT(assertion) \
     (!(assertion) ? \
         (WTFReportAssertionFailure(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, #assertion), \
             CRASH()) : \
         (void)0)
 
-#define DCHECK_AT(assertion, file, line) LAZY_STREAM(logging::LogMessage(file, line, #assertion).stream(), !(assertion))
-
 #define ASSERT_NOT_REACHED() do { \
     WTFReportAssertionFailure(__FILE__, __LINE__, WTF_PRETTY_FUNCTION, 0); \
     CRASH(); \
 } while (0)
 
 #define ASSERT_UNUSED(variable, assertion) ASSERT(assertion)
 
 #define NO_RETURN_DUE_TO_ASSERT NO_RETURN_DUE_TO_CRASH
 
 #else
 
 #define ASSERT(assertion) ((void)0)
-#define DCHECK_AT(assertion, file, line) EAT_STREAM_PARAMETERS
 #define ASSERT_NOT_REACHED() ((void)0)
 #define NO_RETURN_DUE_TO_ASSERT
 
 #define ASSERT_UNUSED(variable, assertion) ((void)variable)
 
 #endif
 
 // ASSERT_WITH_SECURITY_IMPLICATION
 // It is deprecated.  ASSERT_WITH_SECURITY_IMPLICATION should be replaced
 // with SECURITY_DCHECK.
@@ skipping 81 matching lines @@
 } \
 inline const thisType& to##thisType(const argumentType& argumentName) \
 { \
     ASSERT_WITH_SECURITY_IMPLICATION(referencePredicate); \
     return static_cast<const thisType&>(argumentName); \
 } \
 void to##thisType(const thisType*); \
 void to##thisType(const thisType&)
 
 #endif // WTF_Assertions_h