RE: Exception when using printk with CONFIG_CBPRINTF_FP_SUPPORT=y enabled in NCS 1.4.99-dev

CktDesigner — Mon, 18 Jan 2021 19:48:55 GMT

This may have been "pilot error". The original format for the sprintf() used "%5.2f" as the floating point specifier for each of the two float values being reported.

When the sprintf() failed, I removed the "5.2" thinking that perhaps there was a problem with the specification. However the destination for the result had been sized assuming a "shorter" result. So removing the "5.2" made the resulting string longer and (I think) overran the supplied buffer. I think this caused the issue in "str_out()".

Thanks...

RE: Exception when using printk with CONFIG_CBPRINTF_FP_SUPPORT=y enabled in NCS 1.4.99-dev

CktDesigner — Mon, 18 Jan 2021 14:47:58 GMT

Hi Susheel,

Here is a snippet of code where sprintf is used:

    } else if(tempEventConditions[0].signal->result == TEMP_EVENT_DATA) {
      // Data transfer completed; process the data and send it
      int16_t tempCRaw = ((readBuf[0] << 8) | readBuf[1]) / 32;
      float tempC = (float)tempCRaw * 0.125;
      float tempF = (tempC * 1.8) + 32;
      // Put data into appropriate characteristic (rotate through 4)
      tempData[tempCharCntr].tempAmbient=           tempCRaw;
      tempData[tempCharCntr].tempObjectKelvin=      tempCRaw;
      tempData[tempCharCntr].tempObjectCelsius=     tempC;
      tempData[tempCharCntr].tempObjectFahrenheit=  tempF;
      //char strBuf[30];
      sprintf(tempData[tempCharCntr].tempString,"Temp F: %f   Temp C: %f\n",tempF,tempC);
//printk("%s",tempData[tempCharCntr].tempString);
      // Populate the queue item
      tempQueueItem[tempCharCntr].fifo_reserved     = NULL;
      tempQueueItem[tempCharCntr].conn              = bleCurrentConnection;
      tempQueueItem[tempCharCntr].characteristic    = (struct bt_gatt_attr *)&tempService.attrs[5];
      tempQueueItem[tempCharCntr].len               = sizeof(tempDataCharacteristic);
      tempQueueItem[tempCharCntr].data              = (void *)&tempData[tempCharCntr];
      // Send the queue item via the FIFO to the send thread
      k_fifo_put(&notifyQueue,&tempQueueItem[tempCharCntr]);
      // Update tempCharCntr
      tempCharCntr= (tempCharCntr + 1) & NUM_TEMP_BUFFERS_MASK;
    }

As mentioned earlier, this worked in NCS 1.4.0, but I couldn't get 1.4.1 or 1.4.2 to compile due to the MACRO expansion issue shown in the original post.

When 1.4.99-dev is used, sprintf doesn't recognize "%f" as a conversion token (so "%f" is output literally). The CONFIG: CONFIG_CBPRINTF_FP_SUPPORT seems to be needed for this to be overcome, but causes printk (even earlier printk statements that have nothing to do with floating point) to fail in the function str_out().

RE: Exception when using printk with CONFIG_CBPRINTF_FP_SUPPORT=y enabled in NCS 1.4.99-dev

Susheel Nuguru — Mon, 18 Jan 2021 12:34:56 GMT

Hello Ed Hepler.

Could you please attach the code snippet that uses sprintf using %f. I would quickly test to see why it fails in the latest NCS.