Re: [PATCH v3] gdb: c++ify btrace_target_info

[Simon Marchi <simon.marchi@polymtl.ca>]

On 9/8/23 06:53, Markus Metzger wrote:
> Following the example of private_thread_info and private_inferior, turn
> struct btrace_target_info into a small class hierarchy.

IIUC, you turned btrace_tinfo_bts and btrace_tinfo_pt into a single
class, since they were identical?  That seems fine to me.

> 
> Fixes PR gdb/30751.
> ---
>  gdb/nat/linux-btrace.c     | 159 +++++++++++++++++--------------------
>  gdb/nat/linux-btrace.h     |  60 ++++----------
>  gdb/remote.c               |  24 ++----
>  gdbsupport/btrace-common.h |  18 ++++-
>  4 files changed, 112 insertions(+), 149 deletions(-)
> 
> diff --git a/gdb/nat/linux-btrace.c b/gdb/nat/linux-btrace.c
> index c5b3f1c93cf..672b25063de 100644
> --- a/gdb/nat/linux-btrace.c
> +++ b/gdb/nat/linux-btrace.c
> @@ -277,7 +277,7 @@ perf_event_sample_ok (const struct perf_event_sample *sample)
>     part at the end and its upper part at the beginning of the buffer.  */
>  
>  static std::vector<btrace_block> *
> -perf_event_read_bts (struct btrace_target_info* tinfo, const uint8_t *begin,
> +perf_event_read_bts (btrace_target_info *tinfo, const uint8_t *begin,
>  		     const uint8_t *end, const uint8_t *start, size_t size)
>  {
>    std::vector<btrace_block> *btrace = new std::vector<btrace_block>;
> @@ -447,12 +447,19 @@ diagnose_perf_event_open_fail ()
>    error (_("Failed to start recording: %s"), safe_strerror (errno));
>  }
>  
> +/* Get the linux version of a btrace_target_info.  */
> +
> +static linux_btrace_target_info *
> +get_linux_btrace_target_info (btrace_target_info *gtinfo)
> +{
> +  return gdb::checked_static_cast<linux_btrace_target_info *> (gtinfo);
> +}
> +
>  /* Enable branch tracing in BTS format.  */
>  
>  static struct btrace_target_info *
>  linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
>  {
> -  struct btrace_tinfo_bts *bts;
>    size_t size, pages;
>    __u64 data_offset;
>    int pid, pg;
> @@ -460,31 +467,29 @@ linux_enable_bts (ptid_t ptid, const struct btrace_config_bts *conf)
>    if (!cpu_supports_bts ())
>      error (_("BTS support has been disabled for the target cpu."));
>  
> -  gdb::unique_xmalloc_ptr<btrace_target_info> tinfo
> -    (XCNEW (btrace_target_info));
> -  tinfo->ptid = ptid;
> +  std::unique_ptr<linux_btrace_target_info> tinfo
> +    { new linux_btrace_target_info { ptid } };

We recently added a gdb::make_unique function, it would make sense to
you use it here (it will eventually become std::make_unique once we
migrate to C++ 14).

So this could be written as:

  auto tinfo = gdb::make_unique<linux_btrace_target_info> (ptid);

Same for linux_enable_pt.

> diff --git a/gdbsupport/btrace-common.h b/gdbsupport/btrace-common.h
> index e287c93a6c1..b4defdea84c 100644
> --- a/gdbsupport/btrace-common.h
> +++ b/gdbsupport/btrace-common.h
> @@ -214,7 +214,23 @@ struct btrace_data
>  };
>  
>  /* Target specific branch trace information.  */
> -struct btrace_target_info;
> +struct btrace_target_info
> +{
> +  btrace_target_info (ptid_t ptid) : ptid (ptid)
> +    {}
> +
> +  btrace_target_info (ptid_t ptid, btrace_config conf)
> +    : ptid (ptid), conf (conf)
> +    {}
> +
> +  /* The ptid of this thread.  */
> +  ptid_t ptid {};
> +
> +  /* The obtained branch trace configuration.  */
> +  btrace_config conf {};
> +
> +  virtual ~btrace_target_info () = default;

Move the destructor just below the constructors.

With those fixed:

Approved-By: Simon Marchi <simon.marchi@efficios.com>

Simon