Command line editing give a wrong result for me on hush shell 1.9.1

[Denys Vlasenko]

On Monday 18 February 2008 22:36, Martinb_ARM_NOMMU_KISSDVD wrote:
> sorry, bug still there

So, with this code (where I made a slight mistake):

        if (cmdedit_x >= num) {
                const char *bbbb = "\b\b\b\b";
                cmdedit_x -= num;
                if (num <= 4) {
                        bbbb -= num;
 asm volatile("# HERE");
 bb_error_msg("\n bbbb=%02x %02x %02x %02x (%p)", bbbb[0], bbbb[1], bbbb[2], bbbb[3], bbbb);
                        printf(bbbb);
                        return;
                }
                printf("\033[%uD", num);
                return;
        }

You see:

>this is "asdf{backspace}"
>/hdd/newscript # ./hush
>/hdd/newscript # asdfhush:
> bbbb=00 08 08 08 (0x15b4c7f)

and it absolutely correct - bbbb points to a string of
four backspaces, and when num == 1, bbbb is moved back one char.
Your debug output shows exactly this - we moved back, and we see
"xx 08 08 08 08 00" (xx happens to be 00).

BUT NOW I correct that slight mistake:

        if (cmdedit_x >= num) {
                const char *bbbb = "\b\b\b\b";
                cmdedit_x -= num;
 bbbb += 4;
                if (num <= 4) {
                        bbbb -= num;
 asm volatile("# HERE");
 bb_error_msg("\n bbbb=%02x %02x %02x %02x (%p)", bbbb[0], bbbb[1], bbbb[2], bbbb[3], bbbb);
                        printf(bbbb);
                        return;
                }
                printf("\033[%uD", num);
                return;
        }

bbbb should point to THE END (zero byte) of a string of four backspaces,
and when num == 1, bbbb is moved back one char... so it should point
to a string of one backspace and then zero byte - we should see "08 00"

But you see something bogus instead:

> a{backspace}
> /hdd/newscript # ahush:
>  bbbb=20 25 73 00 (0x1559bf7)

I don't understand what's going on.
Can you add yet another debug printout?

        if (cmdedit_x >= num) {
                const char *bbbb = "\b\b\b\b";
 bb_error_msg("\n initial bbbb=%02x %02x %02x %02x (%p)", bbbb[0], bbbb[1], bbbb[2], bbbb[3], bbbb);
                cmdedit_x -= num;
 bbbb += 4;
                if (num <= 4) {
                        bbbb -= num;
 asm volatile("# HERE");
 bb_error_msg("\n bbbb=%02x %02x %02x %02x (%p)", bbbb[0], bbbb[1], bbbb[2], bbbb[3], bbbb);
                        printf(bbbb);
                        return;
                }
                printf("\033[%uD", num);
                return;
        }

and show "a{backspace}" result.
--
vda