Fixes String(float) issue with Stack Smashing (#6138)

Fixes #5873

cores/esp32/WString.cpp

@@ -112,16 +112,28 @@ String::String(unsigned long value, unsigned char base) {
     *this = buf;
 }
 
-String::String(float value, unsigned char decimalPlaces) {
+String::String(float value, unsigned int decimalPlaces) {
     init();
-    char buf[33];
+    char *buf = (char*)malloc(decimalPlaces + 42);
+    if (buf) {
         *this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
+        free(buf);
+    } else {
+        *this = "nan";
+        log_e("No enought memory for the operation.");
+    }
 }
 
-String::String(double value, unsigned char decimalPlaces) {
+String::String(double value, unsigned int decimalPlaces) {
     init();
-    char buf[33];
+    char *buf = (char*)malloc(decimalPlaces + 312);
+    if (buf) {
         *this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
+        free(buf);
+    } else {
+        *this = "nan";
+        log_e("No enought memory for the operation.");
+    }
 }
 
 String::~String() {

cores/esp32/WString.h

@@ -71,8 +71,8 @@ class String {
         explicit String(unsigned int, unsigned char base = 10);
         explicit String(long, unsigned char base = 10);
         explicit String(unsigned long, unsigned char base = 10);
-        explicit String(float, unsigned char decimalPlaces = 2);
-        explicit String(double, unsigned char decimalPlaces = 2);
+        explicit String(float, unsigned int decimalPlaces = 2);
+        explicit String(double, unsigned int decimalPlaces = 2);
         ~String(void);
 
         // memory management

cores/esp32/stdlib_noniso.c

@@ -88,7 +88,7 @@ char* ultoa(unsigned long value, char* result, int base) {
     return result;
 }
 
-char * dtostrf(double number, signed char width, unsigned char prec, char *s) {
+char * dtostrf(double number, signed int width, unsigned int prec, char *s) {
     bool negative = false;
 
     if (isnan(number)) {
@@ -117,7 +117,7 @@ char * dtostrf(double number, signed char width, unsigned char prec, char *s) {
     // Round correctly so that print(1.999, 2) prints as "2.00"
     // I optimized out most of the divisions
     double rounding = 2.0;
-    for (uint8_t i = 0; i < prec; ++i)
+    for (uint32_t i = 0; i < prec; ++i)
         rounding *= 10.0;
     rounding = 1.0 / rounding;
 

cores/esp32/stdlib_noniso.h

@@ -39,7 +39,7 @@ char* utoa (unsigned int val, char *s, int radix);
 
 char* ultoa (unsigned long val, char *s, int radix);
 
-char* dtostrf (double val, signed char width, unsigned char prec, char *s);
+char* dtostrf (double val, signed int width, unsigned int prec, char *s);
 
 #ifdef __cplusplus
 } // extern "C"