Better fix for snprintf non-termination on windows.

core/include/fxcrt/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 _FX_SYSTEM_H_
 #define _FX_SYSTEM_H_
 #define _FX_WIN32_DESKTOP_              1
 #define _FX_LINUX_DESKTOP_              4
@@ skipping 16 matching lines @@
 #elif defined(__APPLE__)
 #define _FX_OS_ _FX_MACOSX_
 #define _FXM_PLATFORM_ _FXM_PLATFORM_APPLE_
 #endif
 #endif
 #if !defined(_FX_OS_) || _FX_OS_ == 0
 #error Sorry, can not figure out what OS you are targeting to. Please specify _FX_OS_ macro.
 #endif
 #if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 #define _CRT_SECURE_NO_WARNINGS
+#include <sal.h>
 #include <windows.h>
-#endif
+#endif  // _FXM_PLATFORM_WINDOWS_
 #define _FX_W32_                1
 #define _FX_W64_                2
 #ifndef _FX_WORDSIZE_
 #if defined(_WIN64) || defined(__arm64) || defined(__arm64__) || defined(_M_AMD64) || defined(_M_X64) || defined(_M_IA64) || defined(__powerpc64__) || defined(__x86_64__) || __WORDSIZE == 64 || defined(__LP64__)
 #define _FX_WORDSIZE_   _FX_W64_
 #else
 #define _FX_WORDSIZE_   _FX_W32_
 #endif
 #endif
 #include <stddef.h>
@@ skipping 81 matching lines @@
 #ifdef _DEBUG
 #define ASSERT FXSYS_assert
 #else
 
 #define ASSERT(a)
 #endif
 #endif
 #define FX_MAX(a, b) (((a) > (b)) ? (a) : (b))
 #define FX_MIN(a, b) (((a) < (b)) ? (a) : (b))
 #define FX_PI   3.1415926535897932384626433832795f
-#if _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
-#define FXSYS_snprintf  _snprintf
-#define FXSYS_vsnprintf _vsnprintf
+
+// 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, _Printf_format_string_ const char* fmt, ...);
+void FXSYS_vsnprintf(char *str, size_t size, const char* fmt, va_list ap);
 #else
-#define FXSYS_snprintf  snprintf
-#define FXSYS_vsnprintf vsnprintf
+#define FXSYS_snprintf  (void) snprintf
+#define FXSYS_vsnprintf (void) vsnprintf
 #endif
+
 #define FXSYS_sprintf   DO_NOT_USE_SPRINTF_DIE_DIE_DIE
 #define FXSYS_vsprintf  DO_NOT_USE_VSPRINTF_DIE_DIE_DIE
 #define FXSYS_strchr    strchr
 #define FXSYS_strlen    strlen
 #define FXSYS_strncmp   strncmp
 #define FXSYS_strcmp    strcmp
 #define FXSYS_strcpy    strcpy
 #define FXSYS_strncpy   strncpy
 #define FXSYS_strstr    strstr
 #define FXSYS_FILE              FILE
@@ skipping 158 matching lines @@
 
 #else  // _FXM_PLATFORM_ == _FXM_PLATFORM_WINDOWS_
 
 #if !defined(PRIuS)
 #define PRIuS "Iu"
 #endif
 
 #endif
 
 #endif