Questions about gdb/mi support on the Mac

Questions about gdb/mi support on the Mac

[Gordon Prieur]

Hi,

    What are the known differences between running gdb/mi on a Mac and
on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
support (via gdb) on the Mac and am seeing significant differences between
the Mac and other platforms.

    For instance, if I send -exec-step on the Mac, I get a *stopped with
reason="end-stepping-range" and thread-id. On all 3 other platforms we
run on I also get a frame parameter (which is what we use to move the PC
and stack annotations.

    Are there other known differences between the Mac and other platforms?
(I'm using gdb 6.3.5 on the Mac).

Thanks,
Gordon

Re: Questions about gdb/mi support on the Mac

[Daniel Jacobowitz]

On Fri, Aug 24, 2007 at 10:50:41AM -0700, Gordon Prieur wrote:
> Hi,
> 
>    What are the known differences between running gdb/mi on a Mac and
> on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
> support (via gdb) on the Mac and am seeing significant differences between
> the Mac and other platforms.

If you are using GDB an Mac OS X, it is Apple's highly customized
version to work with Xcode.  You'd really have to ask them about it -
it's got common ancestry with other versions of GDB, but has changed
quite a lot to work better with their IDE.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Jim Ingham]

As Daniel said, we've pretty freely changed the MI interfaces to make  
them work with ProjectBuilder, then "Project Builder" then Xcode.   
When we started working on this 6 years ago, the MI interfaces were  
pretty rudimentary, so this was necessary.  And there wasn't much  
interest in taking MI changes for the first couple of years we were  
working on it here, so we gradually drifted apart.

There have been several rounds of pulling from our sources to the FSF  
version by various kind folks on the net - though these often  
introduced other subtler differences.  I haven't ever catalogued what  
we've changed, however, so I can't off the top of my head tell you  
what is different.  Most of the changes we made to input syntax are  
documented either in our version of the manual, or in the function  
headers to the mi implementation functions.  The output changes are  
less well documented.  And in our sources we've tried to mark our  
local diffs with "APPLE LOCAL"; but with the MI stuff, where there are  
many whole sections of code that we've added, we are less careful  
about this.

There was a short-lived attempt to rationalize the MI interfaces.  It  
seems to have gone quiet, however - I don't think anybody who's  
actually working on gdb had sufficient motivation to make it worth the  
time it would take to actually do this.

Jim

On Aug 24, 2007, at 11:02 AM, Daniel Jacobowitz wrote:

> On Fri, Aug 24, 2007 at 10:50:41AM -0700, Gordon Prieur wrote:
>> Hi,
>>
>>   What are the known differences between running gdb/mi on a Mac and
>> on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
>> support (via gdb) on the Mac and am seeing significant differences  
>> between
>> the Mac and other platforms.
>
> If you are using GDB an Mac OS X, it is Apple's highly customized
> version to work with Xcode.  You'd really have to ask them about it -
> it's got common ancestry with other versions of GDB, but has changed
> quite a lot to work better with their IDE.
>
> -- 
> Daniel Jacobowitz
> CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Fri, Aug 24, 2007 at 02:02:08PM -0400, Daniel Jacobowitz wrote:
> On Fri, Aug 24, 2007 at 10:50:41AM -0700, Gordon Prieur wrote:
> > Hi,
> > 
> >    What are the known differences between running gdb/mi on a Mac and
> > on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
> > support (via gdb) on the Mac and am seeing significant differences between
> > the Mac and other platforms.
> 
> If you are using GDB an Mac OS X, it is Apple's highly customized
> version to work with Xcode.  You'd really have to ask them about it -
> it's got common ancestry with other versions of GDB, but has changed
> quite a lot to work better with their IDE.

That's disappointing. Does that mean that a front end written to work on
all other platforms with fsf gdb wouldn't work on Mac OS X?

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Eli Zaretskii]

> Date: Fri, 24 Aug 2007 14:43:15 -0400
> From: Bob Rossi <bob_rossi@cox.net>
> 
> > If you are using GDB an Mac OS X, it is Apple's highly customized
> > version to work with Xcode.  You'd really have to ask them about it -
> > it's got common ancestry with other versions of GDB, but has changed
> > quite a lot to work better with their IDE.
> 
> That's disappointing. Does that mean that a front end written to work on
> all other platforms with fsf gdb wouldn't work on Mac OS X?

I think it _will_ work on a Mac, if stock GDB from the FSF sources is
used.  The problem is that the GDB installed by default on a Mac
isn't a stock one, but has extensive changes.

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Sat, Aug 25, 2007 at 12:56:18PM +0300, Eli Zaretskii wrote:
> > Date: Fri, 24 Aug 2007 14:43:15 -0400
> > From: Bob Rossi <bob_rossi@cox.net>
> > 
> > > If you are using GDB an Mac OS X, it is Apple's highly customized
> > > version to work with Xcode.  You'd really have to ask them about it -
> > > it's got common ancestry with other versions of GDB, but has changed
> > > quite a lot to work better with their IDE.
> > 
> > That's disappointing. Does that mean that a front end written to work on
> > all other platforms with fsf gdb wouldn't work on Mac OS X?
> 
> I think it _will_ work on a Mac, if stock GDB from the FSF sources is
> used.  

Well, sure.

> The problem is that the GDB installed by default on a Mac
> isn't a stock one, but has extensive changes.

Yeah, that's very unfortunate. It's to bad apple made such a silly
decision. Think about all the front ends to gdb that won't work on Mac
OS X out of the box. I have users that use cgdb on Mac OS X. It works
because I still use the annotate 2 interface. I'm currently working on
switching over to gdb/mi, it's to bad I'll have to tell my mac
users it won't work.

I think the responsible thing that apple should have done would have
been to make an --interp=mi-apple, which would allow there front end to
work with gdb.

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[André Pönitz]

On Friday 24 August 2007 19:50:41 Gordon Prieur wrote:
> Hi,
> 
>     What are the known differences between running gdb/mi on a Mac and
> on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
> support (via gdb) on the Mac and am seeing significant differences between
> the Mac and other platforms.
> 
>     For instance, if I send -exec-step on the Mac, I get a *stopped with
> reason="end-stepping-range" and thread-id. On all 3 other platforms we
> run on I also get a frame parameter (which is what we use to move the PC
> and stack annotations.
> 
>     Are there other known differences between the Mac and other platforms?
> (I'm using gdb 6.3.5 on the Mac).

One thing I am aware of is the gdb/Mac sometimes produces results
that to not fit into the MI grammar. E.g. when listing locals
it returns:   9^done,locals={{name="a"},{name="w"}}
instead of:   9^done,locals=[{name="a"},{name="w"}]

IIRC (haven't looked at it for a while) also the output for -break-insert
is different.

And (also IIRC) Mac gdb automatically creates MI variables when
running -stack-list-locals.

In case you need details (or want to be sure that I remember correctly ;-))
I can dig through my project history...

Andre'

Re: Questions about gdb/mi support on the Mac

[André Pönitz]

On Friday 24 August 2007 20:43:15 Bob Rossi wrote:
> On Fri, Aug 24, 2007 at 02:02:08PM -0400, Daniel Jacobowitz wrote:
> > On Fri, Aug 24, 2007 at 10:50:41AM -0700, Gordon Prieur wrote:
> > > Hi,
> > > 
> > >    What are the known differences between running gdb/mi on a Mac and
> > > on Windows/Linux/Solaris? I'm debugging problems in netbeans C/C++
> > > support (via gdb) on the Mac and am seeing significant differences between
> > > the Mac and other platforms.
> > 
> > If you are using GDB an Mac OS X, it is Apple's highly customized
> > version to work with Xcode.  You'd really have to ask them about it -
> > it's got common ancestry with other versions of GDB, but has changed
> > quite a lot to work better with their IDE.
> 
> That's disappointing. Does that mean that a front end written to work on
> all other platforms with fsf gdb wouldn't work on Mac OS X?

It doesn't necessarily mean that. 

Mac Gdb/Mi behaves still in most cases like FSF Gdb/Mi, there are only a handful
exceptions that usually need only some minor tweaks like adding a second code
path in the interpretation of the result. 

A bit more annoying is the different set of output data on different platforms
as this means some shortcuts when retrieving  "a full set of data" that can
be taken on one platform does not necessarily work on the other, leading
to either using the lowest common denominator or having even larger separate
code paths.

Andre'

Re: Questions about gdb/mi support on the Mac

[Nick Roberts]

 > >     Are there other known differences between the Mac and other platforms?
 > > (I'm using gdb 6.3.5 on the Mac).
 > 
 > One thing I am aware of is the gdb/Mac sometimes produces results
 > that to not fit into the MI grammar. E.g. when listing locals
 > it returns:   9^done,locals={{name="a"},{name="w"}}

This is old style MI (mi0) output.

 > instead of:   9^done,locals=[{name="a"},{name="w"}]

Looking at Apple's mi-cmd-stack.c:

  cleanup_list = make_cleanup_ui_out_list_begin_end (uiout, locals ? "locals" : "args");

I think it will output the latter now.

 > IIRC (haven't looked at it for a while) also the output for -break-insert
 > is different.

Apple have documented some of their own commands in their version of the
GDB manual.

 > And (also IIRC) Mac gdb automatically creates MI variables when
 > running -stack-list-locals.

It can do with the "--make-varobjs" option but this doesn't seem to be
documented.

 > In case you need details (or want to be sure that I remember correctly ;-))
 > I can dig through my project history...

It's probably enough to say that you will get unreliable behaviour trying 
to use Apple GDB from a frontend that is expecting the MI output of FSF GDB.
If your frontend must run on a Mac then you either need to compile FSF GDB
for the Mac (if that's possible) or read the Apple GDB source/manual and
adapt your frontend accordingly.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: Questions about gdb/mi support on the Mac

[Daniel Jacobowitz]

On Tue, Aug 28, 2007 at 08:55:44PM +1200, Nick Roberts wrote:
> It's probably enough to say that you will get unreliable behaviour trying 
> to use Apple GDB from a frontend that is expecting the MI output of FSF GDB.
> If your frontend must run on a Mac then you either need to compile FSF GDB
> for the Mac (if that's possible)

It isn't.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Tue, Aug 28, 2007 at 06:55:02AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 28, 2007 at 08:55:44PM +1200, Nick Roberts wrote:
> > It's probably enough to say that you will get unreliable behaviour trying 
> > to use Apple GDB from a frontend that is expecting the MI output of FSF GDB.
> > If your frontend must run on a Mac then you either need to compile FSF GDB
> > for the Mac (if that's possible)
> 
> It isn't.

Well, in that case, hopefully people realize that apple is making some
silly decisions by making a monopoly on gdb front ends. Not that I
believe this was there intention, but I do believe it was a
consequence of there irresponsibility.

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Daniel Jacobowitz]

On Tue, Aug 28, 2007 at 07:24:38AM -0400, Bob Rossi wrote:
> Well, in that case, hopefully people realize that apple is making some
> silly decisions by making a monopoly on gdb front ends. Not that I
> believe this was there intention, but I do believe it was a
> consequence of there irresponsibility.

You may want to think about the reality of software development a
little.  They have the only port of GDB to Mac OS X; anyone else could
have done one, but no one did.  They seem to want to contribute it
back, too.  They just never have time.  This is partly because of
the immense schedule pressure at Apple.  It's also partly because of
how much work it is to contribute to GDB.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Nick Roberts]

 > > > If your frontend must run on a Mac then you either need to compile FSF
 > > > GDB for the Mac (if that's possible)
 > > 
 > > It isn't.
 > 
 > Well, in that case, hopefully people realize that apple is making some
 > silly decisions by making a monopoly on gdb front ends. Not that I
 > believe this was there intention, but I do believe it was a
 > consequence of there irresponsibility.

It's not silly and it's not a monopoly.  They're accountable to their
shareholders, not us.  All Apple's changes are released under GPL and available
from their repository.  Anyone can merge them back into FSF GDB, if they wish.
Indeed, we have done some of that in the past.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Tue, Aug 28, 2007 at 11:54:10PM +1200, Nick Roberts wrote:
>  > > > If your frontend must run on a Mac then you either need to compile FSF
>  > > > GDB for the Mac (if that's possible)
>  > > 
>  > > It isn't.
>  > 
>  > Well, in that case, hopefully people realize that apple is making some
>  > silly decisions by making a monopoly on gdb front ends. Not that I
>  > believe this was there intention, but I do believe it was a
>  > consequence of there irresponsibility.
> 
> It's not silly and it's not a monopoly.  They're accountable to their
> shareholders, not us.  All Apple's changes are released under GPL and available
> from their repository.  Anyone can merge them back into FSF GDB, if they wish.
> Indeed, we have done some of that in the past.

Ummm, what would be the point? I'm sure they would continue modifying
GDB and most front ends still wouldn't work with GDB on Mac OS X.
Honestly, I don't care, as I don't use OS X. I'm sure I'll get some
people that aren't happy though. O well.

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Tue, Aug 28, 2007 at 07:33:49AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 28, 2007 at 07:24:38AM -0400, Bob Rossi wrote:
> > Well, in that case, hopefully people realize that apple is making some
> > silly decisions by making a monopoly on gdb front ends. Not that I
> > believe this was there intention, but I do believe it was a
> > consequence of there irresponsibility.
> 
> You may want to think about the reality of software development a
> little.  They have the only port of GDB to Mac OS X; anyone else could
> have done one, but no one did.  They seem to want to contribute it
> back, too.  They just never have time.  This is partly because of
> the immense schedule pressure at Apple.  It's also partly because of
> how much work it is to contribute to GDB.

Ha, the only port of GDB, and it only works with their front end! That
sounds like a monopoly to me. In fact, it sounds like one of the tactics 
msft used when making content for there web browser. I do not 
think that apple would have made this decision on purpose. I'm also not
suggesting some sort of conspiracy theory. I understand how this sort of
issue could have come about, because the original apple programmers
either didn't care, or didn't think about other front ends.

In the future, I think they should be more friendly to the rest of the 
community and there users by either sticking to the mi that GDB supports, 
or making a -i=mi-apple protocol. 

That's just my 2 cents as a front end developer. You can either listen
to it and accept it, or shrug it off as I'm a crazy lunatic.

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Daniel Jacobowitz]

On Tue, Aug 28, 2007 at 08:53:04AM -0400, Bob Rossi wrote:
> Ha, the only port of GDB, and it only works with their front end! That
> sounds like a monopoly to me. In fact, it sounds like one of the tactics 
> msft used when making content for there web browser.

You have a truly bizarre definition of monopoly.  It works fine from
the command line, and we've seen that at least one other front end
developer has managed to make his work with it.  It's just not the
same program named "gdb" that you expect.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Tue, Aug 28, 2007 at 09:13:24AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 28, 2007 at 08:53:04AM -0400, Bob Rossi wrote:
> > Ha, the only port of GDB, and it only works with their front end! That
> > sounds like a monopoly to me. In fact, it sounds like one of the tactics 
> > msft used when making content for there web browser.
> 
> You have a truly bizarre definition of monopoly.  It works fine from
> the command line, and we've seen that at least one other front end
> developer has managed to make his work with it.  It's just not the
> same program named "gdb" that you expect.

OK, when my users say, "hey, why doesn't cgdb work on mac os x anymore?", 
I'll tell them either, "add support to cgdb yourself" or 
"no, really, it's a good thing that apple ported gdb to Mac OS X and
cgdb doesn't work".

This is literally the position I'm in. How do you suggest I reason about
the possibilities I have? Do you have a better possibility for me?

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Daniel Jacobowitz]

On Tue, Aug 28, 2007 at 09:37:33AM -0400, Bob Rossi wrote:
> OK, when my users say, "hey, why doesn't cgdb work on mac os x anymore?", 
> I'll tell them either, "add support to cgdb yourself" or 
> "no, really, it's a good thing that apple ported gdb to Mac OS X and
> cgdb doesn't work".
> 
> This is literally the position I'm in. How do you suggest I reason about
> the possibilities I have? Do you have a better possibility for me?

Would you rather they hadn't ported any GDB to Mac OS X at all?  Tell
your users that Apple's port does not include what cgdb needs.  It's
no different from someone complaining that it doesn't work on any
platform with no GDB port at all.

Or make cgdb cope with the variations.  That's up to you.

-- 
Daniel Jacobowitz
CodeSourcery

Re: Questions about gdb/mi support on the Mac

[Bob Rossi]

On Tue, Aug 28, 2007 at 09:45:36AM -0400, Daniel Jacobowitz wrote:
> On Tue, Aug 28, 2007 at 09:37:33AM -0400, Bob Rossi wrote:
> > OK, when my users say, "hey, why doesn't cgdb work on mac os x anymore?", 
> > I'll tell them either, "add support to cgdb yourself" or 
> > "no, really, it's a good thing that apple ported gdb to Mac OS X and
> > cgdb doesn't work".
> > 
> > This is literally the position I'm in. How do you suggest I reason about
> > the possibilities I have? Do you have a better possibility for me?
> 
> Would you rather they hadn't ported any GDB to Mac OS X at all?  Tell
> your users that Apple's port does not include what cgdb needs.  It's
> no different from someone complaining that it doesn't work on any
> platform with no GDB port at all.

I really don't know. I suppose it's a good thing that apple did the
port.

Actually, I think I'll just point them to this thread, I think I've made
my case fair enough.

Bob Rossi

Re: Questions about gdb/mi support on the Mac

[Gordon Prieur]

Daniel Jacobowitz wrote:
> On Tue, Aug 28, 2007 at 08:53:04AM -0400, Bob Rossi wrote:
>   
>> Ha, the only port of GDB, and it only works with their front end! That
>> sounds like a monopoly to me. In fact, it sounds like one of the tactics 
>> msft used when making content for there web browser.
>>     
>
> You have a truly bizarre definition of monopoly.  It works fine from
> the command line, and we've seen that at least one other front end
> developer has managed to make his work with it.  It's just not the
> same program named "gdb" that you expect.
>   

It took me less than a day to get Apple's gdb working with my NetBeans 
gdb module
(granted, I didn't do much more than sanity test it). So the changes are 
simple and
easily resolved. I expect any other differences I find will also be 
simple to resolve.

Gordon

Re: Questions about gdb/mi support on the Mac

[Nick Roberts]

 > > Anyone can merge them back into FSF GDB, if they wish.  Indeed, we have
 > > done some of that in the past.
 > 
 > Ummm, what would be the point? 

The point is that we can incorporate their good ideas into FSF GDB.

 >                                    I'm sure they would continue modifying
 > GDB and most front ends still wouldn't work with GDB on Mac OS X.

Yes, but that's their prerogative.

-- 
Nick                                           http://www.inet.net.nz/~nickrob

Re: Questions about gdb/mi support on the Mac

[Mark Kettenis]

> From: Nick Roberts <nickrob@snap.net.nz>
> Date: Tue, 28 Aug 2007 23:54:10 +1200
> 
>  > > > If your frontend must run on a Mac then you either need to compile FSF
>  > > > GDB for the Mac (if that's possible)
>  > > 
>  > > It isn't.
>  > 
>  > Well, in that case, hopefully people realize that apple is making some
>  > silly decisions by making a monopoly on gdb front ends. Not that I
>  > believe this was there intention, but I do believe it was a
>  > consequence of there irresponsibility.
> 
> It's not silly and it's not a monopoly.  They're accountable to
> their shareholders, not us.

While that statement may legally be true, at least in the US, I don't
think it is morally right.  Companies have responsibilities to the
society around it, especially the communities they directly interact
with.

Of course Apple realises that they can't just take from the Open
Source community, but also have to give something back.  They did
indeed decide to assign their changes back to the FSF such that they
can be merged back.  But they could (and I believe should) do more
than just that.  There are a couple of companies that use gdb in their
products that are much more active in contributing changes back to us.

Mark