I reconfirmed MS-VC6. Thank you for wonderful correspondence.

bmomjian · bmomjian · commit cd8f3ec599ec · 2005-12-09T04:50:40.000Z
However, Another problem newly occurred.
This solves the problem of snprintf and vsnprintf.

Patch to HEAD and 8.1.X.

Hiroshi Saito
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
@@ -23,6 +23,12 @@
 #define HAVE_RANDOM
 #endif
 
+/* use _snprintf and _vsnprintf */
+#define HAVE_DECL_SNPRINTF 1
+#define snprintf        _snprintf
+#define HAVE_DECL_VSNPRINTF 1
+#define vsnprintf       _vsnprintf
+
 /* defines for dynamic linking on Win32 platform */
 #ifdef __CYGWIN__
 
