Jump without altering the stack

Question

I am trying to make a subroutine that prints a null terminated string, but it doesn't work. in my first attempt:

PRINTLN:   ld   a, (bc)     // set bc to start of string before calling
           add  a, 0        // update zero flag
           jp   z, endprint // if the character at (bc) is a null, terminate loop
           out  1, a        // output to port 0 (TTY in emulator)
           inc  bc          // point to next character
           jp   println     // rinse and repeat
ENDPRINT:  ret              // end of subroutine

it just repeated the string until it stopped for some reason. My emulator won't let me view the stack. The next attempt was to put the address of PRINTLN to de before the loop and then just push de and use ret instead of jp:

PRINTLN:   ld   de, printloop // attempt to get rid of jp's effect on the stack
PRINTLOOP: ld   a, (bc)       // set bc to start of string before calling
           add  a, 0          // update zero flag
           jp   z, endprint   // if the character at (bc) is a null, terminate loop
           out  1, a          // output to port 0 (TTY in emulator)
           inc  bc            // point to next character
           push de            // I hope this works
           ret                // rinse and repeat
ENDPRINT:  ret                // end of subroutine

This ended in a failure too, because it kept repeating the first character of the string for some reason. What is going on and what do I do to fix it?

Answer 1

The emulator is inaccurate. it alters the stack when it executes a jp instruction, even though it shouldn't. I'll look for a different emulator. Don't use the ZEMU emulator.