[PATCH] ash: improve expandstr()

[Denys Vlasenko]

Applied, thanks!

On Thu, Jan 23, 2020 at 12:26 PM Ron Yorston <rmy at pobox.com> wrote:
>
> The dash maintainer recently posted a fix for issues with expanding
> PS1.  These had already been fixed differently in BusyBox ash.  Borrow
> a couple of improvements:
>
> - Use a single call to setjmp() to trap errors in both readtoken1()
>   and expandarg().
>
> - In case of error set the prompt to the literal value of PS1 rather
>   than the half-digested nonsense in stackblock() which might include
>   ugly control characters.
>
> function                                             old     new   delta
> expandstr                                            353     300     -53
>
> Signed-off-by: Ron Yorston <rmy at pobox.com>
> ---
>  shell/ash.c | 40 ++++++++++++++++++++--------------------
>  1 file changed, 20 insertions(+), 20 deletions(-)
>
> diff --git a/shell/ash.c b/shell/ash.c
> index 4b5eafa7c..e87c91ece 100644
> --- a/shell/ash.c
> +++ b/shell/ash.c
> @@ -13098,29 +13098,26 @@ expandstr(const char *ps, int syntax_type)
>         volatile int saveint;
>         struct jmploc *volatile savehandler = exception_handler;
>         struct jmploc jmploc;
> +       const char *volatile result;
> +       int err;
>
>         /* XXX Fix (char *) cast. */
>         setinputstring((char *)ps);
>
>         saveprompt = doprompt;
>         doprompt = 0;
> +       result = ps;
> +
> +       SAVE_INT(saveint);
> +       if ((err=setjmp(jmploc.loc)))
> +               goto out;
>
>         /* readtoken1() might die horribly.
>          * Try a prompt with syntactically wrong command:
>          * PS1='$(date "+%H:%M:%S) > '
>          */
> -       SAVE_INT(saveint);
> -       if (setjmp(jmploc.loc) == 0) {
> -               exception_handler = &jmploc;
> -               readtoken1(pgetc(), syntax_type, FAKEEOFMARK, 0);
> -       }
> -       exception_handler = savehandler;
> -       RESTORE_INT(saveint);
> -
> -       doprompt = saveprompt;
> -
> -       /* Try: PS1='`xxx(`' */
> -       unwindfiles(file_stop);
> +       exception_handler = &jmploc;
> +       readtoken1(pgetc(), syntax_type, FAKEEOFMARK, 0);
>
>         n.narg.type = NARG;
>         n.narg.next = NULL;
> @@ -13130,17 +13127,20 @@ expandstr(const char *ps, int syntax_type)
>         /* expandarg() might fail too:
>          * PS1='$((123+))'
>          */
> -       SAVE_INT(saveint);
> -       if (setjmp(jmploc.loc) == 0) {
> -               exception_handler = &jmploc;
> -               expandarg(&n, NULL, EXP_QUOTED);
> -       } else if (exception_type == EXEXIT) {
> -               exitshell();
> -       }
> +       expandarg(&n, NULL, EXP_QUOTED);
> +       result = stackblock();
> +
> +out:
>         exception_handler = savehandler;
> +       if (err && exception_type != EXERROR)
> +               longjmp(exception_handler->loc, 1);
>         RESTORE_INT(saveint);
>
> -       return stackblock();
> +       doprompt = saveprompt;
> +       /* Try: PS1='`xxx(`' */
> +       unwindfiles(file_stop);
> +
> +       return result;
>  }
>
>  static inline int
> --
> 2.24.1
>
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