src: use standard conform snprintf on windows

The version used before returned -1 on truncation which does not conform
to the standard.

PR-URL: #2404
Reviewed-By: Trevor Norris <trev.norris@gmail.com>
Reviewed-By: Fedor Indutny <fedor@indutny.com>

Author: skomski

src/node_internals.h

@@ -95,17 +95,19 @@ void GetSockOrPeerName(const v8::FunctionCallbackInfo<v8::Value>& args) {
 #ifdef _WIN32
 // emulate snprintf() on windows, _snprintf() doesn't zero-terminate the buffer
 // on overflow...
+// VS 2015 added a standard conform snprintf
+#if defined( _MSC_VER ) && (_MSC_VER < 1900)
 #include <stdarg.h>
-inline static int snprintf(char* buf, unsigned int len, const char* fmt, ...) {
-  va_list ap;
-  va_start(ap, fmt);
-  int n = _vsprintf_p(buf, len, fmt, ap);
-  if (len)
-    buf[len - 1] = '\0';
-  va_end(ap);
-  return n;
+inline static int snprintf(char *buffer, size_t n, const char *format, ...) {
+  va_list argp;
+  va_start(argp, format);
+  int ret = _vscprintf(format, argp);
+  vsnprintf_s(buffer, n, _TRUNCATE, format, argp);
+  va_end(argp);
+  return ret;
 }
 #endif
+#endif
 
 #if defined(__x86_64__)
 # define BITS_PER_LONG 64

test/fixtures/throws_error6.js

@@ -54,11 +54,16 @@ errExec('throws_error4.js', function(err, stdout, stderr) {
   assert.ok(/SyntaxError/.test(stderr));
 });
 
-// Long exception line doesn't result in stack overflow
+// Specific long exception line doesn't result in stack overflow
 errExec('throws_error5.js', function(err, stdout, stderr) {
   assert.ok(/SyntaxError/.test(stderr));
 });
 
+// Long exception line with length > errorBuffer doesn't result in assertion
+errExec('throws_error6.js', function(err, stdout, stderr) {
+  assert.ok(/SyntaxError/.test(stderr));
+});
+
 process.on('exit', function() {
-  assert.equal(5, exits);
+  assert.equal(6, exits);
 });