Re: [PATCH] shell: Fix unsigned char promotion and truncation

["Anders Kaseorg" <andersk@mit.edu>]

On 10/21/25 06:29, Herbert Xu wrote:
> When a char is promoted to an int, it needs to be signed as otherwise
> comparisons on it may fail.  Alternatively, an integer needs to be
> truncated to char before comparing it against another char.
There’s another instance of this in argstr() case CTLMBCHAR:

  		case CTLMBCHAR:
  			c = (signed char)*p--;
  			mb = mbnext(p);
  			ml = (mb >> 8) - 2;
  			if (flag & (QUOTES_ESC | EXP_MBCHAR)) {
  				length = (mb >> 8) + (mb & 0xff);
				if (c == (char)CTLESC)

Since (signed char)CTLESC is negative, it never equals (char)CTLESC on 
unsigned char architectures.

Reproduction:

$ uname -m
aarch64
$ dash -c 'IFS=ë; set -- ${u-a\ëb}; echo $#'
2

(Expected 1, as on x86_64.)

Anders