ENH: MSVS 2013 snprintf compatible substitute

Simplify the backwards compatible snprintf configuration for pre
1900 version of MSVC.  Otherwise prefer C++11 syntax using std::snprintf.

include/json/config.h

@@ -54,6 +54,14 @@
 #define JSON_API
 #endif
 
+#if defined(_MSC_VER) && _MSC_VER < 1900
+// As recommended at https://stackoverflow.com/questions/2915672/snprintf-and-visual-studio-2010
+   extern JSON_API int msvc_pre1900_c99_snprintf(char *outBuf, size_t size, const char *format, ...);
+#  define jsoncpp_snprintf msvc_pre1900_c99_snprintf
+#else
+#  define jsoncpp_snprintf std::snprintf
+#endif
+
 // If JSON_NO_INT64 is defined, then Json only support C++ "int" type for
 // integer
 // Storages, and 64 bits integer support is disabled.

src/jsontestrunner/main.cpp

@@ -28,11 +28,7 @@ struct Options {
 
 static JSONCPP_STRING normalizeFloatingPointStr(double value) {
   char buffer[32];
-#if defined(_MSC_VER) && defined(__STDC_SECURE_LIB__)
-  sprintf_s(buffer, sizeof(buffer), "%.16g", value);
-#else
-  snprintf(buffer, sizeof(buffer), "%.16g", value);
-#endif
+  jsoncpp_snprintf(buffer, sizeof(buffer), "%.16g", value);
   buffer[sizeof(buffer) - 1] = 0;
   JSONCPP_STRING s(buffer);
   JSONCPP_STRING::size_type index = s.find_last_of("eE");
@@ -105,11 +101,7 @@ static void printValueTree(FILE* fout,
     Json::ArrayIndex size = value.size();
     for (Json::ArrayIndex index = 0; index < size; ++index) {
       static char buffer[16];
-#if defined(_MSC_VER) && defined(__STDC_SECURE_LIB__)
-      sprintf_s(buffer, sizeof(buffer), "[%u]", index);
-#else
-      snprintf(buffer, sizeof(buffer), "[%u]", index);
-#endif
+      jsoncpp_snprintf(buffer, sizeof(buffer), "[%u]", index);
       printValueTree(fout, value[index], path + buffer);
     }
   } break;

src/lib_json/json_reader.cpp

@@ -22,21 +22,14 @@
 #if __cplusplus >= 201103L
 #include <cstdio>
 
-#if !defined(snprintf)
-#define snprintf std::snprintf
-#endif
-
 #if !defined(sscanf)
 #define sscanf std::sscanf
 #endif
 #else
-#include <stdio.h>
+#include <cstdio>
 
 #if defined(_MSC_VER)
 #define _CRT_SECURE_CPP_OVERLOAD_STANDARD_NAMES 1
-#if !defined(snprintf)
-#define snprintf _snprintf
-#endif
 #endif
 #endif
 
@@ -813,7 +806,7 @@ JSONCPP_STRING Reader::getLocationLineAndColumn(Location location) const {
   int line, column;
   getLocationLineAndColumn(location, line, column);
   char buffer[18 + 16 + 16 + 1];
-  snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
+  jsoncpp_snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
   return buffer;
 }
 
@@ -1833,7 +1826,7 @@ JSONCPP_STRING OurReader::getLocationLineAndColumn(Location location) const {
   int line, column;
   getLocationLineAndColumn(location, line, column);
   char buffer[18 + 16 + 16 + 1];
-  snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
+  jsoncpp_snprintf(buffer, sizeof(buffer), "Line %d, Column %d", line, column);
   return buffer;
 }
 

src/lib_json/json_value.cpp

@@ -19,6 +19,29 @@
 #include <algorithm> // min()
 #include <cstddef>   // size_t
 
+// Provide implementation equivalent of std::snprintf for older _MSC compilers
+#if defined(_MSC_VER) && _MSC_VER < 1900
+#include <stdarg.h>  
+static int msvc_pre1900_c99_vsnprintf(char *outBuf, size_t size, const char *format, va_list ap)
+{
+    int count = -1;
+    if (size != 0)
+        count = _vsnprintf_s(outBuf, size, _TRUNCATE, format, ap);
+    if (count == -1)
+        count = _vscprintf(format, ap);
+    return count;
+}
+
+int JSON_API msvc_pre1900_c99_snprintf(char *outBuf, size_t size, const char *format, ...)
+{
+    va_list ap;
+    va_start(ap, format);
+    const int count = msvc_pre1900_c99_vsnprintf(outBuf, size, format, ap);
+    va_end(ap);
+    return count;
+}
+#endif
+
 // Disable warning C4702 : unreachable code
 #if defined(_MSC_VER) && _MSC_VER >= 1800 // VC++ 12.0 and above
 #pragma warning(disable : 4702)

src/lib_json/json_writer.cpp

@@ -27,9 +27,6 @@
 #define isfinite std::isfinite
 #endif
 
-#if !defined(snprintf)
-#define snprintf std::snprintf
-#endif
 #else
 #include <math.h>
 #include <stdio.h>
@@ -46,9 +43,6 @@
 #endif
 
 #define _CRT_SECURE_CPP_OVERLOAD_STANDARD_NAMES 1
-#if !defined(snprintf)
-#define snprintf _snprintf
-#endif
 #endif
 
 #if defined(__sun) && defined(__SVR4) // Solaris
@@ -145,7 +139,7 @@ JSONCPP_STRING valueToString(double value,
 
   JSONCPP_STRING buffer(size_t(36), '\0');
   while (true) {
-    int len = snprintf(
+    int len = jsoncpp_snprintf(
         &*buffer.begin(), buffer.size(),
         (precisionType == PrecisionType::significantDigits) ? "%.*g" : "%.*f",
         precision, value);