Segmentation fault when changing value of attribute - c++11

Question

I'm working in a C++11 class that will fetch via I2C the value of a temperature sensor in a Raspberry Pi. It will be polling the value until it's stopped. It does the polling in a separate thread, so that it does not stop the application flow. The problem is that in the line 64 of this file: https://github.com/OpenStratos/server/blob/feature/temperature/temperature/Temperature.cpp#L64
void Temperature::read_temperature()
{
while (this->reading)
{
#ifndef OS_TESTING
int value = wiringPiI2CRead(this->filehandle);
#else
int value = 16000;
#endif
float voltage = value * 5 / 32768; // 2^15
float temp = r_to_c(TEMP_R * (TEMP_VIN / voltage - 1));
this->temperature = temp; // Gives segmentation fault
this_thread::sleep_for(chrono::milliseconds(50));
}
}
it gives a segmentation fault. The curius thing is that it does not always happen. After compiling, running the binary many times about the 75% of the time will crash.
This is the file that invoques the code:https://github.com/OpenStratos/server/blob/feature/temperature/testing/temperature_test.cpp
Temperature temp(20);
temp.start_reading();
AssertThat(temp.is_reading(), Equals(true));
// this_thread::sleep_for(chrono::milliseconds(100)); if uncommented less segmentation faults
temp.stop_reading();
AssertThat(temp.is_reading(), Equals(false));
What could be happening? How can it be fixed?

Answer 1

You need to wait for Temperature::read_temperature() to quit, so you need:
bool reading;
volatile bool stopped; // volatile required to make the compiler re-read
// the value everytime we expect it to.
//
bool is_stopped(){ return stopped; }
and
void Temperature::start_reading()
{
if (!reading)
{
stopped = false;
reading = true;
// etc
and
void Temperature::read_temperature()
{
while (this->reading)
{
// etc
}
stopped=true;
}
and
temp.stop_reading();
while(!temp.is_stopped();
AssertThat(temp.is_reading(), Equals(false));