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cavr

Array is empty in debugger watch

When I look in the debugger watch, with breakpoint at _render, command containins only 0x00. This is for a AVR processor.

int main(){
    char hello[] = "Hello";
    gfx_put_string(5, hello);
}

void gfx_put_string(int length, char* characters){
    char command[length+3];
    command[0] = 0x00; //cmd
    command[1] = 0x06; //cmd
    for (int i=0; i<length; i++){
        command[i+2] = characters[i];
    }
    command[length+2] = 0x00; //end with null
    _render(length+3, command);
}

Want it to contain 0x00, 0x06, H, e, l, l, o, 0x00. What is wrong with my code? How can I fix it?

Edit: Suggested fix was to change the first character in the array not being 0x00 (null), but no change. Optmization is turned of. XC8 None (-O0)

Found it in memory though(?) Image of memory

Solution

  • So the problem was something with the command array being variable length, when I set the length to a const everything worked out as expected. Final code below:

    void gfx_put_string(const int length, char* characters){
    char command[length+3];
    command[0] = 0x00;
    command[1] = 0x06; //cmd
    
    for (int i=0; i<length; i++){
        command[i+2] = characters[i];
    }
    command[length+2] = 0x00; //end with null

   _render(length+3, command);
}