Applied, thanks!
David Bidner, le mer. 07 oct. 2026 05:39:47 +0200, a ecrit:
> The ddb variable table accesses db_max_line, db_max_width and
> db_tab_stop_width through db_expr_t pointers, but their definitions
> use int. On 64-bit kernels, assigning these variables overwrites
> adjacent storage. In particular, setting $lines cleared the tab width
> and caused division by zero during tab expansion.
>
> Define all three variables as db_expr_t. For non-positive tab widths,
> avoid division in NEXT_TAB() and emit pending whitespace as spaces so
> db_force_whitespace() keeps advancing. This also changes invalid-width
> handling on 32-bit kernels.
>
> Tested in the serial-console debugger on i386 and amd64 with tab widths
> 0, -1, 4 and 8; output completed and variable values were preserved.
> ---
> ddb/db_output.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/ddb/db_output.c b/ddb/db_output.c
> index
> 9a76f545604d374f0dfb833dee6b9bf8da195881..bff1de99b0a10fdccbbc15301941cdf6972bf2a2
> 100644
> --- a/ddb/db_output.c
> +++ b/ddb/db_output.c
> @@ -69,11 +69,14 @@
> int db_output_position = 0; /* output column */
> int db_output_line = 0; /* output line number */
> int db_last_non_space = 0; /* last non-space character */
> -int db_tab_stop_width = 8; /* how wide are tab stops? */
> +/* Accessed through db_expr_t pointers in db_variables.c. */
> +db_expr_t db_tab_stop_width = 8; /* how wide are tab stops? */
> #define NEXT_TAB(i) \
> - ((((i) + db_tab_stop_width) / db_tab_stop_width) * db_tab_stop_width)
> -int db_max_line = DB_MAX_LINE; /* output max lines */
> -int db_max_width = DB_MAX_WIDTH; /* output line width */
> + ((db_tab_stop_width > 0) \
> + ? ((((i) + db_tab_stop_width) / db_tab_stop_width) *
> db_tab_stop_width) \
> + : (i))
> +db_expr_t db_max_line = DB_MAX_LINE; /* output max lines */
> +db_expr_t db_max_width = DB_MAX_WIDTH; /* output line width */
>
> /*
> * Force pending whitespace.
> @@ -85,6 +88,12 @@ db_force_whitespace(void)
>
> last_print = db_last_non_space;
> while (last_print < db_output_position) {
> + if (db_tab_stop_width <= 0) {
> + /* Use spaces because NEXT_TAB() cannot advance at this width.
> */
> + cnputc(' ');
> + last_print++;
> + continue;
> + }
> next_tab = NEXT_TAB(last_print);
> if (next_tab <= db_output_position) {
> cnputc('\t');
>
--
Samuel
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