math log() function crashes with reboot.

[cornelalexa]

Hi,

I have a dew point calculation function which use log() and when used the ESP crashes and reboots.
Here is the code for it.

float dewPointFast(float celsius=0, float humidity=0)
{
if(celsius==0 && humidity ==0) return (float) 0.00;
const float a = 17.271;
const float b = 237.7;
float temp = (float)((a * celsius) / (b + celsius));
temp+= log(humidity/100); //this crashes and reboots
float Td = (float)((b * temp) / (a - temp));
return Td;
}

It seems that log10() does the same so it might worth having a look at that too.

Thanks!

[cornelalexa]

Not sure if it helps, below is the data from crash:

ets Jan 8 2013,rst cause:4, boot mode:(3,0)

wdt reset
load 0x40100000, len 28832, room 16
tail 0
chksum 0x80
load 0x3ffe8000, len 1564, room 8
tail 4
chksum 0x8e
load 0x3ffe8620, len 4796, room 4
tail 8
chksum 0x43
csum 0x43
rd

[holgerlembke]

Crashes here, too.

Try to live with that:

float log(float dings) {
static float ln10 = -1;

if (ln10<0) {
ln10 = ln(10);
}
return ln(dings)/ln10;
}

float ln(float x) {
float zw1 = (x-1)/(x+1);
float zw2 =zw1*zw1;
float res = 0;

int c=1;
do {
res+=zw1/c;
c+=2;
zw1*=zw2;
ESP.wdtFeed();
} while (zw1>1/1000.0); // resolution...

return res+res;
}

Oh. And "somethingfloat==somethingother" is always wrong.

[igrr]

Same as #233.

[cornelalexa]

Thank you.

The above functions works as a fix for me. Hope they will be able to fix in the toolchain also. It seems that many functions related to math have issues...

[igrr]

Fixed in esp8266 branch.