On Mon, Apr 12, 2021 at 4:01 PM Stephen Röttger <sroettger@google.com>
wrote:

> From: Stephen Roettger <sroettger@google.com>
>
> When calling `maintenance btrace packet-history` or `maintenance info
> btrace`,
> the commands wouldn't show any data unless it was updated previously by
> some
> other means, for example by running `info record`.
> To fix this, use the require_btrace function from record-brace.h which
> will update the data before returning the btrace_thread_info pointer.
>
> Here's an example of the issue:
> ```
> $ gdb -nx /usr/bin/ls
> (gdb) break malloc
> Breakpoint 1 at 0x46c8
> (gdb) run
> Starting program: /usr/bin/ls
>
> Breakpoint 1, 0x00007ffff7fec240 in malloc () from
> /lib64/ld-linux-x86-64.so.2
> (gdb) record btrace bts
> (gdb) c
> Continuing.
>
> Breakpoint 1, 0x00007ffff7fec240 in malloc () from
> /lib64/ld-linux-x86-64.so.2
> (gdb) maintenance btrace packet-history
> No trace.
> (gdb) maintenance info btrace
> Format: Branch Trace Store.
> Aborted
> ```
>
> gdb/ChangeLog:
>
>         * btrace.c (maint_btrace_packet_history_cmd): use require_btrace
>         (maint_info_btrace_cmd): use require_btrace
>         * record-btrace.c (struct btrace_thread_info): mark non-static
>         * record-btrace.h (require_btrace): export function
>
> ---
>  gdb/btrace.c        | 13 ++-----------
>  gdb/record-btrace.c |  2 +-
>  gdb/record-btrace.h |  7 +++++++
>  3 files changed, 10 insertions(+), 12 deletions(-)
>
> diff --git a/gdb/btrace.c b/gdb/btrace.c
> index c697f37f46c..177e818f0cf 100644
> --- a/gdb/btrace.c
> +++ b/gdb/btrace.c
> @@ -3231,12 +3231,8 @@ maint_btrace_packet_history_cmd (const char *arg,
> int from_tty)
>    struct btrace_thread_info *btinfo;
>    unsigned int size, begin, end, from, to;
>
> -  thread_info *tp = find_thread_ptid (current_inferior (), inferior_ptid);
> -  if (tp == NULL)
> -    error (_("No thread."));
> -
> +  btinfo = require_btrace ();
>    size = 10;
> -  btinfo = &tp->btrace;
>
>    btrace_maint_update_packets (btinfo, &begin, &end, &from, &to);
>    if (begin == end)
> @@ -3372,12 +3368,7 @@ maint_info_btrace_cmd (const char *args, int
> from_tty)
>    if (args != NULL && *args != 0)
>      error (_("Invalid argument."));
>
> -  if (inferior_ptid == null_ptid)
> -    error (_("No thread."));
> -
> -  thread_info *tp = inferior_thread ();
> -
> -  btinfo = &tp->btrace;
> +  btinfo = require_btrace ();
>
>    conf = btrace_conf (btinfo);
>    if (conf == NULL)
> diff --git a/gdb/record-btrace.c b/gdb/record-btrace.c
> index b7b3c91f85d..79a6e47a4a6 100644
> --- a/gdb/record-btrace.c
> +++ b/gdb/record-btrace.c
> @@ -269,7 +269,7 @@ require_btrace_thread (void)
>     Throws an error if there is no thread or no trace.  This function never
>     returns NULL.  */
>
> -static struct btrace_thread_info *
> +struct btrace_thread_info *
>  require_btrace (void)
>  {
>    struct thread_info *tp;
> diff --git a/gdb/record-btrace.h b/gdb/record-btrace.h
> index 8e7bbd90e60..b56e720e5a5 100644
> --- a/gdb/record-btrace.h
> +++ b/gdb/record-btrace.h
> @@ -29,4 +29,11 @@ extern void record_btrace_push_target (void);
>     NULL if the cpu was configured as auto.  */
>  extern const struct btrace_cpu *record_btrace_get_cpu (void);
>
> +/* Update the branch trace for the current thread and return a pointer to
> its
> +   branch trace information struct.
> +
> +   Throws an error if there is no thread or no trace.  This function never
> +   returns NULL.  */
> +extern struct btrace_thread_info * require_btrace (void);
> +
>  #endif /* RECORD_BTRACE_H */
> --
> 2.31.1.295.g9ea45b61b8-goog
>
>