Fix binding of null pointer dereference to reference type

core/fxcrt/include/fx_system.h

 // Copyright 2014 PDFium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 // Original code copyright 2014 Foxit Software Inc. http://www.foxitsoftware.com
 
 #ifndef CORE_FXCRT_INCLUDE_FX_SYSTEM_H_
 #define CORE_FXCRT_INCLUDE_FX_SYSTEM_H_
 
 #include <assert.h>
@@ skipping 85 matching lines @@
 #endif
 
 #ifndef ASSERT
 #ifndef NDEBUG
 #define ASSERT assert
 #else
 #define ASSERT(a)
 #endif
 #endif
 
+#if defined(__clang__) || defined(__GNUC__)
+#define PDFIUM_IMMEDIATE_CRASH() __builtin_trap()
+#else
+#define PDFIUM_IMMEDIATE_CRASH() ((void)(*(volatile char*)0 = 0))
+#endif
+
 // M_PI not universally present on all platforms.
 #define FX_PI 3.1415926535897932384626433832795f
 #define FX_BEZIER 0.5522847498308f
 
 // NOTE: prevent use of the return value from snprintf() since some platforms
 // have different return values (e.g. windows _vsnprintf()), and provide
 // versions that always NUL-terminate.
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_ && _MSC_VER < 1900
 void FXSYS_snprintf(char* str,
                     size_t size,
@@ skipping 210 matching lines @@
 
 // Prevent a function from ever being inlined, typically because we'd
 // like it to appear in stack traces.
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #define NEVER_INLINE __declspec(noinline)
 #else  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #define NEVER_INLINE __attribute__((__noinline__))
 #endif  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 
 #endif  // CORE_FXCRT_INCLUDE_FX_SYSTEM_H_