Re: [PATCH v3] Fix hardware watchpoints in replay mode

[Guinevere Larsen <blarsen@redhat.com>]

On 21/11/2023 17:42, Hannes Domani wrote:
> Changes introduced by commit 9e8915c6cee5c37637521b424d723e990e06d597
> caused a regression that meant hardware watchpoint stops would not
> trigger in reverse execution or replay mode.  This was documented in
> PR breakpoints/21969.
> The problem is that record_check_stopped_by_breakpoint always overwrites
> record_full_stop_reason, thus loosing the TARGET_STOPPED_BY_WATCHPOINT
> value which would be checked afterwards.
>
> This commit fixes that by not overwriting the stop-reason in
> record_full_stop_reason if we're not stopped at a breakpoint.
>
> And the test for hw watchpoints in gdb.reverse/watch-reverse.exp actually
> tested sw watchpoints again, since "set can-use-hw-watchpoints 1"
> doesn't convert enabled watchpoints to use hardware.
> This is fixed by disabling said watchpoint while enabling hw watchpoints.
> The same is not done for gdb.reverse/watch-precsave.exp, since it's not
> possible to use hw watchpoints in restored recordings anyways.
>
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=21969
> ---
I checked again; this patch adds no regression, and fixes the issue that 
you described. Since this patch only relates to reverse execution, I say 
its ready for upstreaming.

Approved-by: Guinevere Larsen <blarsen@redhat.com>

-- 
Cheers,
Guinevere Larsen
She/Her/Hers

>   gdb/record.c                                | 1 -
>   gdb/testsuite/gdb.reverse/watch-reverse.exp | 4 ++++
>   2 files changed, 4 insertions(+), 1 deletion(-)
>
> diff --git a/gdb/record.c b/gdb/record.c
> index f7c82665b05..88235e36da7 100644
> --- a/gdb/record.c
> +++ b/gdb/record.c
> @@ -248,7 +248,6 @@ record_check_stopped_by_breakpoint (const address_space *aspace,
>         return 1;
>       }
>   
> -  *reason = TARGET_STOPPED_BY_NO_REASON;
>     return 0;
>   }
>   
> diff --git a/gdb/testsuite/gdb.reverse/watch-reverse.exp b/gdb/testsuite/gdb.reverse/watch-reverse.exp
> index 6b81a6fdf88..a7126ac9b1d 100644
> --- a/gdb/testsuite/gdb.reverse/watch-reverse.exp
> +++ b/gdb/testsuite/gdb.reverse/watch-reverse.exp
> @@ -118,8 +118,12 @@ gdb_test "continue" \
>       ".*\[Ww\]atchpoint.*ival3.*Old value = 0.*New value = -1.*ival3 = count; ival4 = count;.*" \
>       "watchpoint hit in reverse, fifth time"
>   
> +gdb_test_no_output "disable \$bpnum" "disable non-hw watchpoint"
> +
>   gdb_test_no_output "set can-use-hw-watchpoints 1" "enable hw watchpoints"
>   
> +gdb_test_no_output "enable \$bpnum" "enable hw watchpoint"
> +
>   ###
>   ###
>   ###