Newlib's iprintf ram usage

I’m experimenting with an RTOS and newlib on an LPC2138, and it’s a while I have some random crash. Then I used a 2KB stack, instead of 1KB and everything works. Looks like a stack overflow.

Do somebody know how much stack and heap the newlib iprintf uses?

and the iscanf?

I don’t need exact figures, since they probably vary according to format specifiers ( %d %03i …), just the order of magnitude.