#3163 Variable in different places with --debug and all optimizations disabled

[Sebastian Riedel]

main.c:

#include <stdint.h>

uint8_t overworld[1];

uint8_t rand(){
    return 4;
}

void main(){
    uint8_t try;
    uint8_t visited = 1;
    uint8_t tile = 0;
    uint8_t direction;
    uint8_t last_node = 0;
    uint8_t last_distance = 0;// comment out
    do{
        uint8_t next_tile;
        try = 0;
        direction = 1<<(rand() & 0x3);
        do{
            next_tile = tile;
            direction = direction & 0xF;
            ++try;
        }while(try < 4);
        if(try >= 4){
            --visited;
            ++last_distance;// comment out
        } else {
            if(last_node != 0){
                last_node = 0;
            }
            direction = direction & 0xF;
            overworld[next_tile] |= direction;
            ++visited;
        }
    }while(visited);
}

compile.sh:

#!/bin/sh
CFLAGS="--debug --nolospre --no-peep --nogcse --nooverlay --noinduction --noloopreverse --noinvariant"
CC="${SDCCBIN}sdcc -mgbz80 --fsigned-char -c ${CFLAGS}"
LD="${SDCCBIN}sdldgb -y"
mkdir -p build
${CC} -o build/main.rel main.c
${LD} -nmjwxi build/main.ihx build/main.rel

$ sdcc -v
SDCC : mcs51/z80/z180/r2k/r3ka/gbz80/tlcs90/ez80_z80/ds390/pic16/pic14/TININative/ds400/hc08/s08/stm8/pdk13/pdk14/pdk15 4.0.0 #11528 (Linux)
published under GNU General Public License (GPL)

the cdb file says

S:Lmain.main$direction$1_0$2({1}SC:U),R,0,0,[c]

But it’s actually mostly on stack and just gets loaded into c during the end and the discarded. This makes it hard to debug the code, since the shown value is wrong half of the time.

If the lines ending with // comment out are removed, it’s just placed in c.