[PING][PATCH] [gdb] Improve selftest c_ctrl_unctrl

[Tom de Vries <tdevries@suse.de>]

On 3/26/26 3:04 PM, Tom de Vries wrote:
> Improve selftest c_ctrl_unctrl by exercising all valid inputs of c_iscntrl.
> 

Ping.

Thanks,
- Tom

> Tested on x86_64-linux.
> 
> Suggested-By: Tom Tromey <tom@tromey.com> [1]
> 
> [1] https://sourceware.org/pipermail/gdb-patches/2026-March/226231.html
> ---
>   gdb/utils.c | 24 +++++++++++++++++++++---
>   1 file changed, 21 insertions(+), 3 deletions(-)
> 
> diff --git a/gdb/utils.c b/gdb/utils.c
> index b073bb9fdf3..c8903896081 100644
> --- a/gdb/utils.c
> +++ b/gdb/utils.c
> @@ -3793,12 +3793,30 @@ test_c_ctrl_unctrl ()
>     SELF_CHECK (c_ctrl ('?') == 0x7f);
>     SELF_CHECK (c_unctrl (0x7f) == '?');
>   
> -  /* Consistency check.  */
> -  for (unsigned int i = 0; i < 0x100; i++)
> +  /* Consistency check.
> +
> +     The ctype.h function iscntrl has an int parameter, and defined behavior
> +     for inputs [0, 255] and EOF.  Consequently, iscntrl has undefined
> +     behavior when called with a negative signed char argument (with the
> +     possible exception of EOF, which is a negative int constant).  That
> +     extends to chars on platforms where char == signed char.  Consequently,
> +     to write portable code, iscntrl char and signed char arguments need to be
> +     cast to unsigned char.
> +
> +     The c-ctype.h variant c_iscntrl sidesteps this problem by having defined
> +     behavior for inputs [-128, 255] and not bothering about EOF.
> +
> +     The functions c_ctrl/c_unctrl sidestep this issue by using parameter
> +     type unsigned char instead of int.
> +
> +     So, testing input values [0..255] tests all relevant behavior of
> +     c_ctrl/c_unctrl.  However, we designed these functions to be compatible
> +     with c_iscntrl, so we test for all valid inputs of that function.  */
> +  for (int i = -128; i < 256; i++)
>       {
>         unsigned char ch = i;
>         unsigned char unctrl_ch = c_unctrl (ch);
> -      if (!c_iscntrl (ch))
> +      if (!c_iscntrl (i))
>   	{
>   	  SELF_CHECK (unctrl_ch == ch);
>   	  continue;
> 
> base-commit: edf0ae3b9f1ca23daaa55628683edc9a3360286f