Trouble with floats

[bert]

Hi all!

I'm new to z88dk, and I try to compile a c program written for the sdcc.
The program uses a multiplication between int and float which can be done on compile time. In sdcc it works, but with zcc I got zero as result.
Here is the code:

Code: Select all

#include <stdio.h>
#include <stdint.h>

#define WIDTH  (40)

void do_something( uint8_t param1, uint8_t param2)
{
    printf( "param1: %u\n", param1);
    printf( "param2: %u\n", param2);
}

void main()  
{
    printf( "expect: 18, 20\n");
    do_something( WIDTH * 0.45, WIDTH * 0.5);
}

This is the output:

expect: 18, 20
param1: 0
param2: 0

Just for completness the compiler invocation:

zcc +kc85 -create-app --list --c-code-in-asm -lmath48 -lndos -o float_test main.c

Does anybody have a hint, what I'm doing wrong?

Best regards,
Bert

[alvin]

It is a bug in sccz80; the compiler is generating 0.0 for the two constants "WIDTH * 0.45" and "WIDTH * 0.5".
It works with zsdcc as compiler. I'll post the issue number shortly.

[alvin]

Issue #1007
https://github.com/z88dk/z88dk/issues/1007

[bert]

Great!
After the bugfix the program work as expected.

Best regards,
Bert

[RobertK]

I've noticed another problem with floats on the KC target, it could be a console problem. When you printf() a floating point value, the screen gets broken with vertical stripes.

Code: Select all

// floatcalctest.c - Floating point calculation test
// Author: RobertK, 2018-12-29

// Compile with:
// zcc +gal -create-app -lm -o fct floatcalctest.c
// zcc +zx81 -create-app -lm -startup=2 -o fct_zx81 floatcalctest.c
// zcc +zx80 -create-app -lm -o fct_zx80 floatcalctest.c
// zcc +kc -lndos -lm -create-app floatcalctest.c -o fct_KC85_2-5

#include <stdio.h>

void main()
{   
  printf("\nhello world\n");
  printf("\npress any key to calculate 5*0.1...\n");
  fgetc_cons();        // wait for keypress          
  printf("\n5*0.1 is %.1f\n",5*0.1);
  printf("\npress any key to exit...\n");  
  fgetc_cons();        // wait for keypress          
}

Compile it like this:

Code: Select all

zcc +kc -lndos -lm -create-app floatcalctest.c -o fct_KC85_2-5

Try it in JKCEMU with the system set to e.g. KC85/5.

BTW, using -lmath48 instead of -lm makes no difference.

[dom]

Thanks Robert, I'm guessing this is another index register problem - the port is switched over to use iy rather than ix, but I think the maths libraries aren't.

I'll create iy flavours of the maths libraries and see if that solves the problem.

[dom]

I've switched +kc to an ix/iy swapped version of the maths library and the issue has gone away. This makes sense since the main C library for +kc is also ix/iy swapped.

It looks like the kc goes a bit wrong on exit regardless of what you do, but that's a smaller issue.

BTW, the calculation actually takes place in the compiler in this case...

[stefano]

well done !