Add support for enabling DCHECKs in release mode

src/base/logging.h

 // Copyright 2012 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 V8_BASE_LOGGING_H_
 #define V8_BASE_LOGGING_H_
 
 #include <stdint.h>
 #include <string.h>
 
 #include "src/base/build_config.h"
 
 extern "C" void V8_Fatal(const char* file, int line, const char* format, ...);
 
+#if defined(DEBUG) || defined(DCHECK_ALWAYS_ON)
+#define DCHECK_IS_ON 1
+#else
+#define DCHECK_IS_ON 0
+#endif
+
 
 // The FATAL, UNREACHABLE and UNIMPLEMENTED macros are useful during
 // development, but they should not be relied on in the final product.
-#ifdef DEBUG
+#if DCHECK_IS_ON
 #define FATAL(msg)                              \
   V8_Fatal(__FILE__, __LINE__, "%s", (msg))
 #define UNIMPLEMENTED()                         \
   V8_Fatal(__FILE__, __LINE__, "unimplemented code")
 #define UNREACHABLE()                           \
   V8_Fatal(__FILE__, __LINE__, "unreachable code")
 #else
 #define FATAL(msg)                              \
   V8_Fatal("", 0, "%s", (msg))
 #define UNIMPLEMENTED()                         \
@@ skipping 155 matching lines @@
 namespace base {
 
 // Exposed for making debugging easier (to see where your function is being
 // called, just add a call to DumpBacktrace).
 void DumpBacktrace();
 
 } }  // namespace v8::base
 
 
 // The DCHECK macro is equivalent to CHECK except that it only
-// generates code in debug builds.
-#ifdef DEBUG
+// generates code in debug builds or if DCHECK_ALWAYS_ON is defined.
+#if DCHECK_IS_ON
 #define DCHECK_RESULT(expr)    CHECK(expr)
 #define DCHECK(condition)      CHECK(condition)
 #define DCHECK_EQ(v1, v2)      CHECK_EQ(v1, v2)
 #define DCHECK_NE(v1, v2)      CHECK_NE(v1, v2)
 #define DCHECK_GE(v1, v2)      CHECK_GE(v1, v2)
 #define DCHECK_LT(v1, v2)      CHECK_LT(v1, v2)
 #define DCHECK_LE(v1, v2)      CHECK_LE(v1, v2)
 #else
 #define DCHECK_RESULT(expr)    (expr)
 #define DCHECK(condition)      ((void) 0)
 #define DCHECK_EQ(v1, v2)      ((void) 0)
 #define DCHECK_NE(v1, v2)      ((void) 0)
 #define DCHECK_GE(v1, v2)      ((void) 0)
 #define DCHECK_LT(v1, v2)      ((void) 0)
 #define DCHECK_LE(v1, v2)      ((void) 0)
 #endif
 
 #define DCHECK_NOT_NULL(p)  DCHECK_NE(NULL, p)
 
 // "Extra checks" are lightweight checks that are enabled in some release
 // builds.
 #ifdef ENABLE_EXTRA_CHECKS
 #define EXTRA_CHECK(condition) CHECK(condition)
 #else
 #define EXTRA_CHECK(condition) ((void) 0)
 #endif
 
 #endif  // V8_BASE_LOGGING_H_