Increase buffer size in order to avoid buffer overflow when using large floating point numbers

aentinger · aentinger · commit 754873c4cf38 · 2020-12-09T10:30:19.000+01:00
diff --git a/api/String.cpp b/api/String.cpp
@@ -23,6 +23,8 @@
 #include "itoa.h"
 #include "deprecated-avr-comp/avr/dtostrf.h"
 
+#include <float.h>
+
 /*********************************************/
 /*  Constructors                             */
 /*********************************************/
@@ -111,15 +113,17 @@ 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.

Original file line number	Diff line number	Diff line change
`@@ -23,6 +23,8 @@`
`23`	`23`	`#include "itoa.h"`
`24`	`24`	`#include "deprecated-avr-comp/avr/dtostrf.h"`
`25`	`25`
	`26`	`+#include <float.h>`
	`27`	`+`
`26`	`28`	`/*********************************************/`
`27`	`29`	`/* Constructors */`
`28`	`30`	`/*********************************************/`
`@@ -111,15 +113,17 @@ String::String(unsigned long value, unsigned char base)`
`111`	`113`
`112`	`114`	`String::String(float value, unsigned char decimalPlaces)`
`113`	`115`	`{`
	`116`	`+ static size_t const FLOAT_BUF_SIZE = FLT_MAX_10_EXP + FLT_MAX_DECIMAL_PLACES + 1 /* '-' / + 1 / '.' / + 1 / '\0' */;`
`114`	`117`	`init();`
`115`		`- char buf[33];`
	`118`	`+ char buf[FLOAT_BUF_SIZE];`
`116`	`119`	`*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);`
`117`	`120`	`}`
`118`	`121`
`119`	`122`	`String::String(double value, unsigned char decimalPlaces)`
`120`	`123`	`{`
	`124`	`+ static size_t const DOUBLE_BUF_SIZE = DBL_MAX_10_EXP + DBL_MAX_DECIMAL_PLACES + 1 /* '-' / + 1 / '.' / + 1 / '\0' */;`
`121`	`125`	`init();`
`122`		`- char buf[33];`
	`126`	`+ char buf[DOUBLE_BUF_SIZE];`
`123`	`127`	`*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);`
`124`	`128`	`}`
`125`	`129`