Increase buffer size in order to avoid buffer overflow when using lar…

…ge floating point numbers
arduino · Dec 9, 2020 · 952d776 · 952d776
1 parent f3cfa2f
commit 952d776
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Showing 2 changed files with 18 additions and 4 deletions.
diff --git a/api/String.cpp b/api/String.cpp
@@ -23,11 +23,20 @@
 #include "itoa.h"
 #include "deprecated-avr-comp/avr/dtostrf.h"
 
+#include <float.h>
+
+namespace arduino {
+
 /*********************************************/
-/*  Constructors                             */
+/*  Static Member Initialisation             */
 /*********************************************/
 
-namespace arduino {
+size_t const String::FLT_MAX_DECIMAL_PLACES;
+size_t const String::DBL_MAX_DECIMAL_PLACES;
+
+/*********************************************/
+/*  Constructors                             */
+/*********************************************/
 
 String::String(const char *cstr)
 {
@@ -111,15 +120,17 @@ String::String(unsigned long value, unsigned char base)
 
 String::String(float value, unsigned char decimalPlaces)
 {
+	static size_t const FLOAT_BUF_SIZE = FLT_MAX_10_EXP + FLT_MAX_DECIMAL_PLACES + 1 /* '-' */ + 1 /* '.' */ + 1 /* '\0' */;
 	init();
-	char buf[33];
+	char buf[FLOAT_BUF_SIZE];
 	*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
 }
 
 String::String(double value, unsigned char decimalPlaces)
 {
+	static size_t const DOUBLE_BUF_SIZE = DBL_MAX_10_EXP + DBL_MAX_DECIMAL_PLACES + 1 /* '-' */ + 1 /* '.' */ + 1 /* '\0' */;
 	init();
-	char buf[33];
+	char buf[DOUBLE_BUF_SIZE];
 	*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
 }
 

diff --git a/api/String.h b/api/String.h
@@ -58,6 +58,9 @@ class String
 	typedef void (String::*StringIfHelperType)() const;
 	void StringIfHelper() const {}
 
+	static size_t const FLT_MAX_DECIMAL_PLACES = 10;
+	static size_t const DBL_MAX_DECIMAL_PLACES = FLT_MAX_DECIMAL_PLACES;
+
 public:
 	// constructors
 	// creates a copy of the initial value.