Removed ftoa NaN check

NaN check may not work with optimizing compilers. Use your implementation specific NaN check if necessary

printf.c

@@ -223,10 +223,11 @@ static size_t _ftoa(double value, char* buffer, size_t maxlen, unsigned int prec
   // powers of 10
   static const double pow10[] = { 1, 10, 100, 1000, 10000, 100000, 1000000, 10000000, 100000000, 1000000000 };
 
-  // test for NaN
+  // test for negative
-  if (!(value == value) && (maxlen > 2U)) {
+  bool negative = false;
-    buffer[0] = 'n'; buffer[1] = 'a'; buffer[2] = 'n';
+  if (value < 0) {
-    return (size_t)3U;
+    negative = true;
+    value = 0 - value;
   }
 
   // limit precision
@@ -238,12 +239,6 @@ static size_t _ftoa(double value, char* buffer, size_t maxlen, unsigned int prec
     prec = 9U;
   }
 
-  unsigned int negative = 0U;
-  if (value < 0) {
-    negative = 1U;
-    value = 0 - value;
-  }
-
   int whole = (int)value;
   double tmp = (value - whole) * pow10[prec];
   unsigned long frac = (unsigned long)tmp;