Re: [PATCH 2/2] gdb/python: add gdb.Breakpoint.addresses property

[Andrew Burgess <aburgess@redhat.com>]

Simon Farre via Gdb-patches <gdb-patches@sourceware.org> writes:

> Currently it's not possible from the Python API to know
> where a breakpoint has been installed in memory.
>
> This attribute returns a list of the addresses where
> this breakpoint has been installed. This reflects
> the same information shown by the command `info b`.
>
> If the breakpoint is pending it will return None,
> but also if the breakpoint is not of type "breakpoint"
> or "watchpoint" it will also return none.
>
> The rationale for this patch is for IDE or debug adapters
> as they are called, for instance for VSCode, to be able
> to fetch breakpoint related data directly from Python,
> but also useful for plugins that need to query information
> about breakpoints.

I agree that this is a problem that needs to be solved.  Unfortunately,
I don't think this is the right approach to take here.

I think that we should introduce a BreakpointLocation object, which
should encapsulate the information here.

The reason is that GDB has the ability to enable and disable breakpoints
at the individual location level, so we would at a minimum support:

  BreakpointLocation.address : read-only, a single address, which
  corresponds to what you're adding here,

  BreakpointLocation.enabled : read/write, can enable/disable a single
  location,

  BreapointLocation.breakpoint : read-only, the parent breakpoint
  object,

I'm sure we would probably end up adding more functionality over time,
but I think once the we've got the object in place then we have the
framework for future work in place.

Then we'd obviously want to add:

  Breakpoint.locations : read-only, a list of BreakpointLocation
  objects.

I know this is initially much more work, but I think it will give a
better solution in the end.

Thanks,
Andrew
  



> ---
>  gdb/NEWS                   |  5 +++++
>  gdb/doc/python.texi        |  6 ++++++
>  gdb/python/py-breakpoint.c | 26 ++++++++++++++++++++++++++
>  3 files changed, 37 insertions(+)
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index 9e7e41d3bd6..1410c7027e8 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -21,6 +21,11 @@
>       Breakpoint was installed. This is the information displayed
>       by the 'info breakpoints' command.
>  
> +  ** Added attribute Breakpoint.addresses
> +     This returns a list of addresses (as longs) where the
> +     breakpoint was installed. This is the same address information
> +     displayed by the 'info breakpoint' command
> +
>  *** Changes in GDB 12
>  
>  * DBX mode is deprecated, and will be removed in GDB 13
> diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
> index 0d842af6229..3511b8b00a4 100644
> --- a/gdb/doc/python.texi
> +++ b/gdb/doc/python.texi
> @@ -6074,6 +6074,12 @@ breakpoint or is of a type that doesn't have a source location related to it
>  it returns @code{None}. This attribute is not writable.
>  @end defvar
>  
> +@defvar Breakpoint.addresses
> +This attribute holds the address(es) where the breakpoint was installed.
> +If the breakpoint is a pending breakpoint, it returns @code{None}.
> +This attribute is not writable.
> +@end defvar
> +
>  @node Finish Breakpoints in Python
>  @subsubsection Finish Breakpoints
>  
> diff --git a/gdb/python/py-breakpoint.c b/gdb/python/py-breakpoint.c
> index 1b9ac6957a5..19c7cec815c 100644
> --- a/gdb/python/py-breakpoint.c
> +++ b/gdb/python/py-breakpoint.c
> @@ -721,6 +721,30 @@ static PyObject* bppy_get_source_locations(PyObject *self, void* closure)
>    return list.release();
>  }
>  
> +/* Python function to get all addresses where this breakpoint is set  */
> +
> +static PyObject* bppy_get_addresses(PyObject *self, void* closure)
> +{
> +  gdbpy_breakpoint_object *self_bp = (gdbpy_breakpoint_object *) self;
> +  struct breakpoint* bp = self_bp->bp;
> +
> +  BPPY_REQUIRE_VALID (self_bp);
> +
> +  if (pending_breakpoint_p(bp))
> +    Py_RETURN_NONE;
> +
> +  if (!is_breakpoint(bp) && !is_watchpoint(bp))
> +    Py_RETURN_NONE;
> +
> +  gdbpy_ref<> list (PyList_New (0));
> +
> +  for (const bp_location* it = bp->loc; it != nullptr; it = it->next)
> +    if(PyList_Append(list.get(), PyLong_FromLong(it->address)) != 0)
> +      return nullptr;
> +
> +  return list.release();
> +}
> +
>  /* Internal function to validate the Python parameters/keywords
>     provided to bppy_init.  */
>  
> @@ -1295,6 +1319,8 @@ or None if no condition set."},
>      "Whether this breakpoint is a pending breakpoint."},
>    { "source_locations", bppy_get_source_locations, NULL,
>      "Source file locations where this breakpoint is installed"},
> +  { "addresses", bppy_get_addresses, NULL,
> +    "Get addresses of where this breakpoint is set" },
>    { NULL }  /* Sentinel.  */
>  };
>  
> -- 
> 2.32.0