Skip to content

Increase buffer size for converting floats + doubles to String's #5369

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
wants to merge 1 commit into
base: master
Choose a base branch
from
Open

Increase buffer size for converting floats + doubles to String's #5369

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 4 additions & 2 deletions hardware/arduino/avr/cores/arduino/WString.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/

#include <float.h>

#include "WString.h"

/*********************************************/
Expand Down Expand Up @@ -108,14 +110,14 @@ String::String(unsigned long value, unsigned char base)
String::String(float value, unsigned char decimalPlaces)
{
init();
char buf[33];
char buf[FLT_MAX_10_EXP + 4 + decimalPlaces]; // +4, one for: 10, -, ., \0
Copy link
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

What do you mean with "10" there? I can understand how -, . and \0 are added to the number of digits that FLT_MAX_10_EXP represents, but not what 10 means.

Copy link

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

10 as in ascii 10, being a LineFeed perhaps ?

Copy link
Contributor Author

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

On AVR DBL_MAX_10_EXP is 38 and Serial.println(String(-DBL_MAX)); prints out -340282350000000000000000000000000000000.00.

Which is 43 characters in length, then you need an extra byte for the \0, which brings us to 44.

44 - 38 - 2 = 4. Maybe, I was thinking the extra character was for the 1's digit ...

*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
}

String::String(double value, unsigned char decimalPlaces)
{
init();
char buf[33];
char buf[DBL_MAX_10_EXP + 4 + decimalPlaces]; // +4, one for: 10, -, ., \0
*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
}

Expand Down
6 changes: 4 additions & 2 deletions hardware/arduino/sam/cores/arduino/WString.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,8 @@
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/

#include <float.h>

#include "WString.h"
#include "itoa.h"
#include "avr/dtostrf.h"
Expand Down Expand Up @@ -110,14 +112,14 @@ String::String(unsigned long value, unsigned char base)
String::String(float value, unsigned char decimalPlaces)
{
init();
char buf[33];
char buf[FLT_MAX_10_EXP + 4 + decimalPlaces]; // +4, one for: 10, -, ., \0
*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
}

String::String(double value, unsigned char decimalPlaces)
{
init();
char buf[33];
char buf[DBL_MAX_10_EXP + 4 + decimalPlaces]; // +4, one for: 10, -, ., \0
*this = dtostrf(value, (decimalPlaces + 2), decimalPlaces, buf);
}

Expand Down