Clean up some assertion code in WebKit.

third_party/WebKit/Source/wtf/Assertions.h

Index: third_party/WebKit/Source/wtf/Assertions.h
diff --git a/third_party/WebKit/Source/wtf/Assertions.h b/third_party/WebKit/Source/wtf/Assertions.h
index c69fc6246e9a7f1e0abae58e3c879b330c3372fd..6fe194a44bc33f8ee0d0850b2ddf7e538a042b30 100644
--- a/third_party/WebKit/Source/wtf/Assertions.h
+++ b/third_party/WebKit/Source/wtf/Assertions.h
@@ -186,6 +186,8 @@ private:
 #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) \
@@ -194,8 +196,6 @@ private:
             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(); \
@@ -208,7 +208,6 @@ private:
 #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