Fix snprintf emulation for Windows

* Move it into separate win32_snprintf.h file to de-duplicate its
  implementation from all miniupnp source files.

* Do not use this emulation with mingw32 SDK when __NO_ISOCEXT is not
  defined as in this case mingw32 provides working snprintf function.

* Fix detection for mingw-w64 variants, when __NO_ISOCEXT is defined or
  when older version without UCRT is used.

* Add check if _scprintf function is available. In case it is not available
  just returns length of filled buffer to prevent buffer overflow.

miniupnpc/connecthostport.c

@@ -19,11 +19,7 @@
 #include <ws2tcpip.h>
 #include <io.h>
 #define MAXHOSTNAMELEN 64
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #define herror
 #define socklen_t int
 #else /* #ifdef _WIN32 */

miniupnpc/minisoap.c

@@ -13,11 +13,7 @@
 #ifdef _WIN32
 #include <io.h>
 #include <winsock2.h>
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #else
 #include <unistd.h>
 #include <sys/types.h>

miniupnpc/minissdpc.c

@@ -20,11 +20,7 @@
 #include <ws2tcpip.h>
 #include <io.h>
 #include <iphlpapi.h>
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #if !defined(_MSC_VER)
 #include <stdint.h>
 #else /* !defined(_MSC_VER) */

miniupnpc/miniupnpc.c

@@ -15,11 +15,7 @@
 #include <ws2tcpip.h>
 #include <io.h>
 #include <iphlpapi.h>
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #define strdup _strdup
 #ifndef strncasecmp
 #if defined(_MSC_VER) && (_MSC_VER >= 1400)

miniupnpc/miniwget.c

@@ -15,11 +15,7 @@
 #include <ws2tcpip.h>
 #include <io.h>
 #define MAXHOSTNAMELEN 64
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #define socklen_t int
 #ifndef strncasecmp
 #if defined(_MSC_VER) && (_MSC_VER >= 1400)

miniupnpc/upnpc.c

@@ -11,11 +11,7 @@
 #include <time.h>
 #ifdef _WIN32
 #include <winsock2.h>
-/* snprintf is supported by Visual Studio 2015, mingw-w64 8.0.0, mingw-w64 with ucrt, mingw-w64 or mingw32 with ansi stdio */
+#include "win32_snprintf.h"
-#if (defined(_MSC_VER) && _MSC_VER < 1900) || (defined(__MINGW64_VERSION_MAJOR) && __MINGW64_VERSION_MAJOR < 8 && !defined(_UCRT) && !defined(__USE_MINGW_ANSI_STDIO)) || (defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && !defined(__USE_MINGW_ANSI_STDIO))
-/* _snprintf does not fill nul byte at the end of buffer and returns -1 on overflow */
-#define snprintf(buf, size, fmt, ...) ((_snprintf((buf), (size), (fmt), __VA_ARGS__), (((char *)buf)[(size_t)(size)-1] = 0), _scprintf((fmt), __VA_ARGS__)))
-#endif
 #else
 /* for IPPROTO_TCP / IPPROTO_UDP */
 #include <netinet/in.h>

miniupnpc/win32_snprintf.h

@@ -0,0 +1,71 @@
+/* vim: tabstop=4 shiftwidth=4 noexpandtab
+ * MiniUPnP project
+ * http://miniupnp.free.fr/ or https://miniupnp.tuxfamily.org/
+ * (c) 2020 Pali Rohár
+ * This software is subject to the conditions detailed
+ * in the LICENCE file provided within the distribution */
+
+#ifndef WIN32_SNPRINTF_H
+#define WIN32_SNPRINTF_H
+
+#ifdef _WIN32
+
+#include <stdio.h>
+
+/* snprintf is supported by:
+ *  - Visual Studio 2015 or new
+ *  - mingw32 with iso c ext
+ *  - mingw-w64 with ansi stdio
+ *  - mingw-w64 6.0.0 or new with ucrt
+ *  - mingw-w64 8.0.0 or new with iso c ext
+ */
+#if ( \
+	(defined(_MSC_VER) && _MSC_VER < 1900) /* Visual Studio older than 2015 */ || \
+	(defined(__MINGW32__) && !defined(__MINGW64_VERSION_MAJOR) && defined(__NO_ISOCEXT)) /* mingw32 without iso c ext */ || \
+	(defined(__MINGW64_VERSION_MAJOR) && /* mingw-w64 not ... */ !( \
+		(defined (__USE_MINGW_ANSI_STDIO) && __USE_MINGW_ANSI_STDIO != 0)) /* ... with ansi stdio */ || \
+		(__MINGW64_VERSION_MAJOR >= 6 && defined(_UCRT)) /* ... at least 6.0.0 with ucrt */ || \
+		(__MINGW64_VERSION_MAJOR >= 8 && !defined(__NO_ISOCEXT)) /* ... at least 8.0.0 with iso c ext */ || \
+	0) || \
+0)
+
+/* _scprintf is supported by:
+ *  - Visual Studio 2002 or new
+ *  - msvcr70.dll or new
+ *  - msvcrt.dll on Windows XP or new
+ */
+#if ( \
+	(defined(_MSC_VER) && _MSC_VER < 1300) /* Visual Studio older than 2002 */ || \
+	(defined(__MSVCRT_VERSION__) && __MSVCRT_VERSION__ < 0x700) /* msvcrt older than 7.0 */ || \
+0)
+#define CHECK_SCPRINTF 0
+#define IF_SCPRINTF(expr) 0
+#define ELSE_SCPRINTF(expr) expr
+#else
+#define CHECK_SCPRINTF 1
+#define IF_SCPRINTF(expr) expr
+#define ELSE_SCPRINTF(expr) 0
+#endif
+
+/* Emulation of snprintf for win32 */
+#define snprintf(buf, size, fmt, ...) ( \
+	(((size) != 0 && (buf) != NULL) ? ( /* _snprintf does not work with NULL buffer */ \
+		_snprintf((buf), (size), (fmt), __VA_ARGS__), /* _snprintf returns -1 on overflow, so ignore its value */ \
+		(((char *)buf)[(size_t)(size)-1] = 0), /* _snprintf does not fill nul byte on overflow */ \
+	0) : 0), \
+	(CHECK_SCPRINTF ? IF_SCPRINTF( \
+		_scprintf((fmt), __VA_ARGS__) /* calculate return value for snprintf via _scprintf */ \
+	) : ELSE_SCPRINTF( \
+		((size) != 0 && (buf) != NULL) ? \
+			strlen((buf)) /* return just length of buffer */ \
+		: \
+			1 /* no buffer, impossible to calculate, return just non-zero number */ \
+		) \
+	) \
+)
+
+#endif
+
+#endif /* _WIN32 */
+
+#endif /* WIN32_SNPRINTF_H */