archer/tromey patches left to merge

archer/tromey patches left to merge

[Phil Muldoon]

Currently we still have some patches in the archer tromey/python
branch.  I want to finally close this branch, so I decided to write an
email about what is left, and try to decide what we should do about
those patches.  Here is what we have left:

* The -P, --python command line switch

  This feature changes interpretation of the command line so that the
  argument immediately following this switch is taken to be the name
  of a Python script file.  This option stops option processing;
  subsequent options are passed to Python as sys.argv.

* gdb.cli() command.

  This invokes a GDB command-line from a Python script.  Usage of this
  command (AFAIK) is exclusively with the -P switch. (You cannot run
  this command from the gdb command line -- it generates an error
  about recursive instantiatiations.)

  I understand why this exists (to invoke an interactive GDB
  command-line from a Python script), but I feel a little dubious
  about it.  Can we can construct a solid-use case for it?

* maint set python auto-load.

  Enable/disable the auto-loading of Python scripts when an object
  file is opened.

  I think this patch is dead.  It has been superseded by a the more
  generic and powerful gdb auto-load commands.

* require command.

  This command loads on demand a Python script that registers a gdb
  command and which has not been auto-loaded at start-up.  This makes
  it easier to load GDB commands written in Python.
  
* ignore_errors command.

  A wrapper which executes a single command, ignoring and suppressing
  all errors.

  I think this patch is dead.  Users can deal with these exceptions
  independently.

* pahole command.

  Show the holes in a structure.  Takes a type. Comment on those areas
  where it thinks it detects a hole.

  I think this command is generally useful.  I think I remember some
  comments about some problems with it.  I am hoping the discussion
  regarding the problems can be rewritten and posted here.

* caller_is convenience function.

  This function determines if the calling function's name is equal to
  a string that is passed to it.  It takes an optional argument to
  traverse n stack frames to find the function.

  I think this a useful convenience function.  It returns Boolean
  values, so is useful in GDB via the $ convenience variable
  functionality.  An additional option that would be useful would be
  the ability to tell the function to traverse the entire stack.

* caller_matches convenience function.

  Same as above, but use re.match for the comparison.  I think this
  functionality should be rolled into caller_is.

* in_scope convenience function.

  Return true if all the given variables and macros provided to it are
  in scope.  This function takes a variable amount of arguments, and
  will only Return true if all the arguments are in scope.  

There are a few other bits and pieces in there.  Most, as far as I can
determine, are just some orphaned bits of code.

So, lets decide what we want to port to upstream and what we can get
rid of.

Cheers,

Phil

Re: archer/tromey patches left to merge

[Tom Tromey]

Phil> * gdb.cli() command.
[...]
Phil>   I understand why this exists (to invoke an interactive GDB
Phil>   command-line from a Python script), but I feel a little dubious
Phil>   about it.  Can we can construct a solid-use case for it?

The idea is to be able to write a "mostly invisible" invocation of gdb.
That is, start gdb on some program and run it; perhaps setting
breakpoints or whatever in a script; and have this gdb not print
anything and otherwise be as invisible as possible.  Then, if something
"interesting" happens, start up the gdb CLI.

Phil> * maint set python auto-load.
Phil>   I think this patch is dead.  It has been superseded by a the more
Phil>   generic and powerful gdb auto-load commands.

Yes.

Phil> * require command.
Phil>   This command loads on demand a Python script that registers a gdb
Phil>   command and which has not been auto-loaded at start-up.  This makes
Phil>   it easier to load GDB commands written in Python.
  
This is obsolete.  We automatically load these things now.

Phil> * ignore_errors command.
Phil>   A wrapper which executes a single command, ignoring and suppressing
Phil>   all errors.
Phil>   I think this patch is dead.  Users can deal with these exceptions
Phil>   independently.

No, not dead, this comes up pretty regularly.
There was some upstream discussion about whether we want this or the old
"try-catch" patch that is in bugzilla.

Phil> * pahole command.

Phil>   Show the holes in a structure.  Takes a type. Comment on those areas
Phil>   where it thinks it detects a hole.

Phil>   I think this command is generally useful.  I think I remember some
Phil>   comments about some problems with it.  I am hoping the discussion
Phil>   regarding the problems can be rewritten and posted here.

I think there are bugs with virtual bases; and it only prints in C
syntax.

One alternative idea would be to simply make this an option to ptype.
That's probably better most of the time.

Phil> * caller_is convenience function.

Definitely upstream.

Phil> * caller_matches convenience function.

Phil>   Same as above, but use re.match for the comparison.  I think this
Phil>   functionality should be rolled into caller_is.

I don't see how to roll it in, but definitely worth having upstream.

Phil> * in_scope convenience function.

Phil>   Return true if all the given variables and macros provided to it are
Phil>   in scope.  This function takes a variable amount of arguments, and
Phil>   will only Return true if all the arguments are in scope.  

I don't know whether this one is useful or not.
There was a "bad" patch for this functionality upstream, so I wrote this
function to show how it could be done.

Tom

Re: archer/tromey patches left to merge

[Phil Muldoon]

On 14/10/13 15:37, Tom Tromey wrote:
> Phil> * gdb.cli() command.
> [...]

Thanks for the reply Tom.  Here is my plan, pending other comments.

* Merge caller_is and caller_matches functions.

  I will keep them as two separate functions.  My first thought was to
  achieve the results of both with optional keyword arguments, but
  after investigating a little this would probably end up with a
  function heavily loaded with conditional keyword arguments.  It
  removes simplicity and adds complexity, so going with how it stands
  now.  I will add the option to search the entire stack.  I will need
  to write tests and documentation for both.

* Merge -P and gdb.cli()

  These two patches will be merged as one submission as they seem to
  be complimentary in a use-case sense.  I will need to write tests
  and documentation for both.  The -P tests and the gdb.cli() tests
  seem to be non-trivial in the GDB test suite.

* Merge ignore_errors command.

  Tom provided a case that it is needed.  Needs tests and
  documentation.

* Merge in_scope function.

  I think this is useful, so I will port it.  Needs test and
  documentation.  (As an aside, I am not sure where we should document
  these python only functions.  Will discuss.)

* Merge pahole command.

  I am not sure how to make this language agnostic, or even how to
  make it complimentary with ptype.  (We will discuss this more when
  the time-slot arrives in my schedule to consider the effort of
  porting it).
  
That's the order I intend to work on them as time allows.  Lastly, I
will delete the defunct code orphans and remove the obsoleted commands
from the branch.

Cheers,

Phil

Re: archer/tromey patches left to merge

[Tom Tromey]

Phil> * Merge pahole command.

Phil>   I am not sure how to make this language agnostic, or even how to
Phil>   make it complimentary with ptype.  (We will discuss this more when
Phil>   the time-slot arrives in my schedule to consider the effort of
Phil>   porting it).
  
The idea would be to put it in the C code.

A separate commands, as it is now, is definitely simpler.
I think it is just a bit odd from a UI perspective.

Tom