Implement Dump-on-DCHECK (via alternate DCHECK and DCHECK_OP macro implementations).

base/logging.h

Index: base/logging.h
diff --git a/base/logging.h b/base/logging.h
index 07674698e0220dbd7d2ab1662556e2853adc275d..fe015b58bf796cb1863cff7389024a70c964bdf0 100644
--- a/base/logging.h
+++ b/base/logging.h
@@ -637,11 +637,17 @@ enum { DEBUG_MODE = ENABLE_DLOG };
 
 #if DCHECK_IS_ON()
 
+// If DCHECK is configured to dump-without-crashing then omit these, so that
+// anything using them directly will break the build. See crbug.com/596231.
+#if !defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 #define COMPACT_GOOGLE_LOG_EX_DCHECK(ClassName, ...) \
   COMPACT_GOOGLE_LOG_EX_FATAL(ClassName , ##__VA_ARGS__)
 #define COMPACT_GOOGLE_LOG_DCHECK COMPACT_GOOGLE_LOG_FATAL
 const LogSeverity LOG_DCHECK = LOG_FATAL;
 
+#endif  // !defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 #else  // DCHECK_IS_ON()
 
 // These are just dummy values.
@@ -660,6 +666,10 @@ const LogSeverity LOG_DCHECK = LOG_INFO;
 #if defined(_PREFAST_) && defined(OS_WIN)
 // See comments on the previous use of __analysis_assume.
 
+#if defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+#error "Only one of _PREFAST_ and DCHECK_IS_DUMP_WITHOUT_CRASH may be set"
+#endif  // defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 #define DCHECK(condition)                                               \
   __analysis_assume(!!(condition)),                                     \
   LAZY_STREAM(LOG_STREAM(DCHECK), false)                                \
@@ -670,7 +680,19 @@ const LogSeverity LOG_DCHECK = LOG_INFO;
   LAZY_STREAM(PLOG_STREAM(DCHECK), false)                               \
   << "Check failed: " #condition ". "
 
-#else  // _PREFAST_
+#elif DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+// DCHECK is configured to dump-without-crashing, rather than logging.
+// Since we only intend to enable this in official builds, we follow the
+// example of CHECK_OP etc in official builds, and strip out logging.
+// See crbug.com/596231.
+
+BASE_EXPORT void DCheckDumpWithoutCrashing();
+
+#define DCHECK(condition) !(condition) ? ::logging::DCheckDumpWithoutCrashing() : EAT_STREAM_PARAMETERS
+
+#define DPCHECK(condition) DCHECK(condition)
+
+#else  // DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
 
 #define DCHECK(condition)                                                \
   LAZY_STREAM(LOG_STREAM(DCHECK), DCHECK_IS_ON() ? !(condition) : false) \
@@ -680,10 +702,22 @@ const LogSeverity LOG_DCHECK = LOG_INFO;
   LAZY_STREAM(PLOG_STREAM(DCHECK), DCHECK_IS_ON() ? !(condition) : false) \
       << "Check failed: " #condition ". "
 
-#endif  // _PREFAST_
+#endif  // DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
 
 // Helper macro for binary operators.
 // Don't use this macro directly in your code, use DCHECK_EQ et al below.
+
+#if DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+// DCHECK is configured to dump-without-crashing, rather than logging.
+// Since we only intend to enable this in official builds, we follow the
+// example of CHECK_OP etc in official builds, and strip out logging.
+// See crbug.com/596231.
+
+#define DCHECK_OP(name, op, val1, val2) \
+  DCHECK((val1) op (val2))

[ncarter (slow), 2016/04/14 18:41:34]

This looks correct.

[Wez, 2016/04/14 19:54:39]

Unfortunately, though, there is an operator<<(ostream, enum class) in the
TouchHandle code that becomes an "unused function" with this version, so I need
to fix that first.

+
+#else  // DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 // The 'switch' is used to prevent the 'else' from being ambiguous when the
 // macro is used in an 'if' clause such as:
 // if (a == 1)
@@ -699,6 +733,8 @@ const LogSeverity LOG_DCHECK = LOG_INFO;
     logging::LogMessage(__FILE__, __LINE__, ::logging::LOG_DCHECK,    \
                         true_if_passed.message()).stream()
 
+#endif  // DCHECK_IS_ON() && defined(DCHECK_IS_DUMP_WITHOUT_CRASH)
+
 // Equality/Inequality checks - compare two values, and log a
 // LOG_DCHECK message including the two values when the result is not
 // as expected.  The values must have operator<<(ostream, ...)