Re: [PATCH, doc RFA] Add ability to set random attributes in python objfiles,progspaces

[Phil Muldoon <pmuldoon@redhat.com>]

On 09/10/14 20:08, Doug Evans wrote:
> Hi.
>
> I have a need to do some extra record keeping in progspaces and
> objfiles.  This patch adds the ability to add random attributes
> to objfile and progspace objects using the same mechanism used
> for gdb.Fields.
>
> Regression tested on amd64-linux.
>
> 2014-10-09  Doug Evans  <dje@google.com>
>
>     * NEWS: Mention ability add attributes to gdb.Objfile and
>     gdb.Progspace objects.
>     * python/py-objfile.c (objfile_object): New member dict.
>     (objfpy_dealloc): Py_XDECREF dict.
>     (objfpy_initialize): Initialize dict.
>     (objfile_getset): Add __dict__.
>     (objfile_object_type): Set tp_dictoffset member.
>     * python/py-progspace.c (progspace_object): New member dict.
>     (pspy_dealloc): Py_XDECREF dict.
>     (pspy_initialize): Initialize dict.
>     (pspace_getset): Add __dict__.
>     (pspace_object_type): Set tp_dictoffset member.
>
>     doc/
>     * gdb.texinfo (Progspaces In Python): Document ability to add
>     random attributes to gdb.Progspace objects.
>     (Objfiles In Python): Document ability to add random attributes to
>     gdb.objfile objects.
>
>     testsuite/
>     * gdb.python/py-objfile.exp: Add tests for setting random attributes
>     in objfiles.
>     * gdb.python/py-progspace.exp: Add tests for setting random attributes
>     in progspaces.
>
> diff --git a/gdb/NEWS b/gdb/NEWS
> index b56fe8e..ec43a22 100644
> --- a/gdb/NEWS
> +++ b/gdb/NEWS
> @@ -9,6 +9,7 @@
> 
>    ** You can now access frame registers from Python scripts.
>    ** New attribute 'producer' for gdb.Symtab objects.
> +  ** You can now add attributes to gdb.Objfile and gdb.Progspace objects.
> 
>  * New Python-based convenience functions:
> 
> diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
> index 81ec11b..14a2181 100644
> --- a/gdb/doc/python.texi
> +++ b/gdb/doc/python.texi
> @@ -3356,6 +3356,10 @@ The @code{frame_filters} attribute is a dictionary of frame filter
>  objects.  @xref{Frame Filter API}, for more information.
>  @end defvar
> 
> +One may add arbitrary attributes to @code{gdb.Progspace} objects.
> +This is useful if for example one needs to do some extra record keeping
> +associated with the progspace.

Maybe add a small example here as you did with gdb.Objfile?  Or maybe
an xref.  One of my goals in the next year is to add (and backfill in
existing documentation) more example led documentation for Python.
Sometimes an example speaks (ten) thousand words!


> +@smallexample
> +(gdb) python
> +import datetime
> +def new_objfile_handler (event):
> +    event.new_objfile.time_loaded = datetime.datetime.today ()
> +gdb.events.new_objfile.connect (new_objfile_handler)
> +end
> +(gdb) file ./hello
> +Reading symbols from ./hello...done.
> +(gdb) python print gdb.objfiles()[0].time_loaded
> +2014-10-09 11:41:36.770345
> +@end smallexample

This is really awesome example. (Linking in from comment above).
Thanks for taking the time out to provide a "useful" example that is
also simple.


>  A @code{gdb.Objfile} object has the following methods:
> 
>  @defun Objfile.is_valid ()
> diff --git a/gdb/python/py-objfile.c b/gdb/python/py-objfile.c
> index df29691..32bceee 100644
> --- a/gdb/python/py-objfile.c
> +++ b/gdb/python/py-objfile.c
> @@ -30,6 +30,9 @@ typedef struct
>    /* The corresponding objfile.  */
>    struct objfile *objfile;
> 
> +  /* Dictionary holding user-added attributes.  */
> +  PyObject *dict;
> +

My only nit here is the naming.  dict is kind of generic.  I know it
follows on from the fields code :( Even though you wrote a comment,
later use in the code means (say a year from now), I have to
remember what this mysterious "dict" is.  I'll volunteer to fix up the
fields code. Lately I have been writing variable names that at least
have an indication of actual usage in GDB beyond a description of what
the variable is.  So I would write that to be something like,
attribute_dict or something along those lines.  Anyway just a nit.  If
you decide not to pursue my comments, it is no show-stopper.

> --- a/gdb/python/py-progspace.c
> +++ b/gdb/python/py-progspace.c
> @@ -32,6 +32,9 @@ typedef struct
>    /* The corresponding pspace.  */
>    struct program_space *pspace;
> 
> +  /* Dictionary holding user-added attributes.  */
> +  PyObject *dict;
> +
>    /* The pretty-printer list of functions.  */
>    PyObject *printers;

Same comments as above with the dict name.

Thanks for this patch.  It seems really useful (and in implementation
fairly simple to implement).  I wonder if there are other objects in
Python that could benefit from the ability to arbitrarily record
keep?

Cheers

Phil