IOT instruction (core dumped)

[teackot]

A simple program with 2 delays:

#ifndef F_CPU
#define F_CPU 9600000UL // 9.6 MHz clock speed
#endif

#include <stdbool.h>
#include <util/delay.h>
#include <avr/io.h>

int main() {
    DDRB |= 1;

    while (true) {
        PORTB |= 1;
        _delay_ms(300);
        PORTB &= ~1;
        _delay_ms(50);
    }
}

Launched with:

simavr -m attiny13 -f9600000 -g cmake-build-debug-avr/avr-hello-world

Gives:

Loaded 1204 .text at address 0x0
Loaded 0 .data
IOT instruction (core dumped)  simavr -m attiny13 -f9600000 -g cmake-build-debug-avr/avr-hello-world

However, if you leave only one _delay_ms or compile for another MCU (I tried ATMega328), program runs fine

[edgar-bonet]

I could not reproduce this issue with simavr master (7003af0). I get instead:

Loaded 82 bytes at 0
avr_gdb_init listening on port 1234

However, this line you showed looks suspicious:

Loaded 1204 .text at address 0x0

This cannot fit in an ATtiny13, and is also way too big for such a simple program. Did you forget to enable optimizations? If so, you should have seen this compiler message:

warning: #warning "Compiler optimizations disabled; functions from <util/delay.h> won't work as designed" [-Wcpp]

If I attempt to load the unoptimized program (which is too large) with simavr, I get

Loaded 1090 bytes at 0
Aborted

[gatk555]

It works well for me also. I can even see a lamp flashing:

If the size of the flash segment is the problem, adding option "-v" to the command will confirm it, as there is a error message for the problem. (There is a plausible PR to show error messages by default.) I think that is the right explanation, as "IOT instruction" is probably some shell's anachronistic way of saying "Aborted". (SIGIOT and SIGABRT are the same thing. I think it was the PDP-11 that actually had an IOT instruction!)

When I tried to compile without optimisation, the oversized flash was reported, with no output file:

In file included from attiny13_510.c:6:0:
/usr/lib/avr/include/util/delay.h:112:3: warning: #warning "Compiler optimizations disabled; functions from <util/delay.h> won't work as designed" [-Wcpp]

/usr/lib/gcc/avr/5.4.0/../../../avr/bin/ld: attiny13_510.axf section .text' will not fit in region text'
collect2: error: ld returned 1 exit status

Building for an Atmega, then running on the Tiny13 fixed that, and I also saw "Aborted" and the message with "-v".

[teackot]

Sorry for the late answer.

Did you forget to enable optimizations

Yes, this was the problem. Enabling optimizations reduced the output size from 1204 B to 44 B and it now fits in ATtiny13

If the size of the flash segment is the problem, adding option "-v" to the command will confirm it

Now with -v it shows an actual error message: avr_loadcode(): Attempted to load code of size 1204 but flash size is only 1024.