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check boundaries converting float/double to String #613

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1a6a417
check boundaries converting float/double to String
pennam Oct 29, 2025
db1b6a0
use FLT_MAX_10_EXP and DBL_MAX_10_EXP instead of hardcoded values
pennam Nov 28, 2025
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16 changes: 14 additions & 2 deletions cores/arduino/WString.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,6 +20,14 @@
*/

#include "WString.h"
#include <float.h>

/*********************************************/
/* Static Member Initialisation */
/*********************************************/

size_t const String::FLT_MAX_DECIMAL_PLACES;
size_t const String::DBL_MAX_DECIMAL_PLACES;

/*********************************************/
/* Constructors */
Expand Down Expand Up @@ -107,15 +115,19 @@ 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];
decimalPlaces = decimalPlaces < FLT_MAX_DECIMAL_PLACES ? decimalPlaces : FLT_MAX_DECIMAL_PLACES;
*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];
decimalPlaces = decimalPlaces < DBL_MAX_DECIMAL_PLACES ? decimalPlaces : DBL_MAX_DECIMAL_PLACES;
*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
}

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3 changes: 3 additions & 0 deletions cores/arduino/WString.h
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Original file line number Diff line number Diff line change
Expand Up @@ -50,6 +50,9 @@ 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.
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