TinyGPS++ Crashes ESP32 (and probably others)

Development Platforms
1

Code first, all necessary documentation at the bottom. This does not seem like the correct place but this is where the link took me to post questions/problems.

#include <TinyGPS++.h>

TinyGPSPlus gps;


void setup() {

  Serial.begin(115200);
  for (float fAngle = -180.; fAngle < 400.; fAngle++) {
    Serial.printf("fAngle = %.0f ", fAngle);
    Serial.printf("Cardinal %s\n", gps.cardinal(fAngle));
  }
}

void loop() {

//fAngle = -180 Cardinal 
//fAngle = -179 Cardinal 
//fAngle = -178 Cardinal 
//...  All OK, until....
//fAngle = -58 Cardinal 
//fAngle = -57 Cardinal 
//fAngle = -56 

Guru Meditation Error: Core  1 panic'ed (LoadProhibited). Exception was unhandled.
//Core 1 register dump:
//PC      : 0x400014fd  PS      : 0x00060530  A0      : 0x800d8208  A1      : 0x3ffb1ae0  
//A2      : 0x00000000  A3      : 0xfffffffc  A4      : 0x000000ff  A5      : 0x0000ff00  
//A6      : 0x00ff0000  A7      : 0xff000000  A8      : 0x00000000  A9      : 0x3ffb1e20  
//A10     : 0x00000003  A11     : 0x00060123  A12     : 0x00060120  A13     : 0x00000020  
//A14     : 0x00000020  A15     : 0x00000000  SAR     : 0x0000001f  EXCCAUSE: 0x0000001c  
//EXCVADDR: 0x00000000  LBEG    : 0x400014fd  LEND    : 0x4000150d  LCOUNT  : 0xffffffff  
//
//Backtrace: 0x400014fd:0x3ffb1ae0 0x400d8205:0x3ffb1af0 0x400df736:0x3ffb1e00 0x400df76e:0x3ffb1e90 0x400d0ca8:0x3ffb1ed0 0x400d09ca:0x3ffb1f70 0x400e4047:0x3ffb1fa0
//
//Rebooting...
//ets Jun  8 2016 00:22:57
//
//rst:0xc (SW_CPU_RESET),boot:0x13 (SPI_FAST_FLASH_BOOT)
//configsip: 0, SPIWP:0xee
//clk_drv:0x00,q_drv:0x00,d_drv:0x00,cs0_drv:0x00,hd_drv:0x00,wp_drv:0x00
//mode:DIO, clock div:1
//load:0x3fff0018,len:4
//load:0x3fff001c,len:952
//load:0x40078000,len:6084
//load:0x40080000,len:7936
//entry 0x40080310
//fAngle = -180 Cardinal 
//...and so it goes, over and over.
}
2

The code has a bug. Following the cardinal() function (here):

const char *TinyGPSPlus::cardinal(double course)
{
  static const char* directions[] = {"N", "NNE", "NE", "ENE", "E", "ESE", "SE", "SSE", "S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW"};
  int direction = (int)((course + 11.25f) / 22.5f);
  return directions[direction % 16];
}

You see if it expects course to never be negative, because that would yield a negative direction and direction % 16 value. It computes direction % 16 to be a negative number, and thus you get something like directions[-7] returned, which is behind the start of the actual array:

#include <Arduino.h>

//Code from
//https://github.com/mikalhart/TinyGPSPlus/blob/master/src/TinyGPS%2B%2B.cpp#L330
const char *cardinal(double course) {
	static const char* directions[] = { "N", "NNE", "NE", "ENE", "E", "ESE",
			"SE", "SSE", "S", "SSW", "SW", "WSW", "W", "WNW", "NW", "NNW" };
	int direction = (int) ((course + 11.25f) / 22.5f);
	Serial.println("Chosen index: " + String(direction % 16));
	return directions[direction % 16];
}

void setup() {
	Serial.begin(115200);
	for (float fAngle = -180.; fAngle < 400.; fAngle++) {
		Serial.printf("fAngle = %.0f ", fAngle);
		Serial.printf("Cardinal %s\n", cardinal(fAngle));
	}
}

void loop() {
}

Outputs

fAngle = -180 Chosen index: -7
Cardinal

The easy fix would be taking the angle modulo 360 and that it is always positive. An easy fix would be to add

	//is it negative?
	while(course < 0.0) {
		course += 360.0;
	}

or

	course = fmod(course, 360.0);
	if(course < 0.0)
		course += 360.0;

(with #include <math.h>)

at the start of the cardinal() function. Now it gives you

fAngle = -180 Chosen index: 8
Cardinal S

I.e. -180° is actually south now and it doesn’t crash.

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