GDB paper accepted for GCC summit

GDB paper accepted for GCC summit

[PAUL GILLIAM]

I have not received official word yet, but the following URL strongly
suggests that my proposal for a paper at the upcoming gcc summit has
been accepted.

http://www.gccsummit.org/2006/speakers.php

I was afraid that might happen.

Here is the abstract:
        
        Recent Developments in GDB 
        
        Many programmers on many platforms depend on GDB to help them
        find and fix bugs in their programs.  Some of these programmers
        use GDB directly and others indirectly through one of several
        available graphical front-ends. 
        
        This paper summarizes major changes in GDB over the last few
        years, starting with the release of GDB 6.0.  These changes were
        made in a number of areas, including: support for additional
        architectures; internal changes and reorganizations aimed at
        better supporting current and future architectures; new features
        to help programmers debug their programs; and enhancements to
        make GDB easier to use both for those who use it directly and
        for those who write and maintain front ends.  
        
        Also included is an overview of the GDB community and how it
        operates, touching on a recent overhaul in the way the community
        interrelates to improve GDB.
        
I would really like to just be the editor and let *you*, the real GDB
experts, write it.  I think that would be best for the GDB community,
and definitely for me 8-).

Failing that, I would like suggestions of which developments I should
research, using the News file, mailing lists, ChangeLog, and source code
as the sources.

Either way, I am depending on the GDB community to review the paper and
keep me from making a total fool of myself.

I will be gone all next week, so *please* send me your ideas, sentences,
paragraphs, sections, or heckles so that I can get a running start when
I begin work on the paper when I return.

-=# Paul Gilliam #=-

PS:  Here is what I have so far, with out doing any research; depending
on my sieve-like memory.

New architectures and systems:

        ????

Internal changes and reorganizations:

        * New framework for stack unwinding.
        * More object-oriented ideas. Example: observers.
        
New user features:

        * Checkpoints.
        
Enhancements:

        * More robust and useful MI interface.
        * Support for ADA (or is this a new user feature?)
        
Community reorganization:

        * Patch champions. 
        
As you can see, I have a lot of work to do and I really need your help.
(I'm not begging too much, am I?)
        
        

Re: GDB paper accepted for GCC summit

[Eli Zaretskii]

> From: PAUL GILLIAM <pgilliam@us.ibm.com>
> Date: Fri, 17 Mar 2006 14:05:47 -0800
> 
> Failing that, I would like suggestions of which developments I should
> research, using the News file, mailing lists, ChangeLog, and source code
> as the sources.

The NEWS file should be the starting point.  We try to make a point of
mentioning there every noteworthy user-level change.

Re: GDB paper accepted for GCC summit

[PAUL GILLIAM]

Hi all,

I gleaned this from the NEWS file and have a few questions.

Mult-arched targets
	HP/PA HPUX11			6.0
	Renesas M32R/D  w/simulator     6.0
	DEC Alpha			<6.0
	DEC VAX				<6.0
	NEC V850			<6.0
	National Semi. NS32000 (part)   <6.0
	Motorola 68000 (part)		<6.0
	Motorola MCORE			<6.0

New Architectures
	Morpho Technologies ms2		>6.4

New Native Configurations
	OpenBSD arm			6.4
	OpenBDS mips64			6.4
	GNU/Linux m32r			6.3
	GNU/Linux hppa			6.2
	OpenBSD m68k			6.2
	OpenBSD m88k			6.2
	OpenBSD PowerPC			6.2
	NetBSD VAX			6.2
	OpenBSD VAX			6.2
	NetBSD amd64			6.1
	OpenBSD amd64			6.1
	OpenBSD alpha			6.1
	OpenBSD sparc			6.1
	OpenBSD sparc64			6.1

New Targets
	Morpho Technologies ms1		6.4

Removed configureations
	VxWorks and XDR protocol        6.4
	Motorola MCORE			6.4
	National Semiconductor NS32000  6.4
	Sun 3, running SunOS 3		6.2
	Sun 3, running SunOS 4		6.2
	Sun 2, running SunOS 3		6.2
	Sun 2, running SunOS 4		6.2
	LynxOS				6.1
	SunOS 4				6.1
	SGI Irix-4.x			6.1
	SGI Iris (MIPS) run. Irix V3:   6.1
	Z8000 simulator			6.1
	Matsushita MN10200 w/simulator  6.1
	H8/500 simulator		6.1
	HP/PA running BSD		6.1
	HP/PA running OSF/1		6.1
	HP/PA Pro target		6.1
	PMAX (MIPS) running Mach 3.0    6.1
	386BSD				6.1
	Sequent family			6.1
	SPARC running LynxOS		6.1
	SPARC running SunOS 4		6.1
	Tsqware Sparclet		6.1
	Fujitsu SPARClite		6.1
	V850EA ISA			6.0
	Motorola Delta 88000 run. Sys V	6.0
	IBM AIX PS/2			6.0
	i386 running Mach 3.0		6.0
	i386 running Mach		6.0
	i386 running OSF/1		6.0
	HP/Apollo 68k Family		6.0
	Argonaut Risc Chip (ARC)        6.0
	Mitsubishi D30V			6.0
	Fujitsu FR30			6.0
	OS/9000				6.0
	I960 with MON960		6.0
	
Obsolete configurations
	h8300				6.3
	mcore				6.3
	mn10300				6.3
	ns32k				6.3
	sh64				6.3
	v850				6.3
	Sun 3, running SunOS 3		6.1
	Sun 3, running SunOS 4		6.1
	Sun 2, running SunOS 3		6.1
	Sun 2, running SunOS 4		6.1
	Motorola 680x0 running LynxOS   6.1
	AT&T 3b1/Unix pc		6.1
	Bull DPX2 (68k, SVR3)		6.1
	decstation			6.1
	riscos				6.1
	sonymips			6.1
	sysv				6.1
	Z8000 simulator			6.0
	Matsushita MN10200 w/simulator  6.0
	H8/500 simulator		6.0
	HP/PA running BSD		6.0
	HP/PA running OSF/1		6.0
	HP/PA Pro target		6.0
	PMAX (MIPS) running Mach 3.0    6.0
	Sequent family			6.0
	Tsqware Sparclet		6.0
	Fujitsu SPARClite		6.0

QUESTIONS:

1) What is the difference between 'New Architectures' and 'New Targets'?
   Has there realy only be one of each sense 6.0?

2) These seem to removed in the given release, but not obsoleted first.
   Is this correct? 
	386BSD, 6.1
	SGI Iris (MIPS) running Irix V3, 6.1
	SGI Irix-4.x, 6.1
	SPARC running LynxOS, 6.1
	SPARC running SunOS 4, 6.1
	SunOS 4, 6.1
	VxWorks and XDR protocol, 6.4

3) These seem to have be obsoleted in the given release, but never
   removed.  Is this correct?
  	AT&T 3b1/Unix pc, 6.1
	Bull DPX2 (68k, SVR3), 6.1
	decstation, 6.1
	h8300, 6.3
	mn10300, 6.3
	Motorola 680x0 running LynxOS, 6.1
	riscos, 6.1 
	sh64, 6.3
	sonymips, 6.1
	sysv, 6.1
	v850, 6.3

4) What's up with 'Multi-arch'?  It is mentioned for 5.3 and 6.0, but
   not again. The 'V850' was multi-arched in 5.3 and then removed in
   6.0, without being    obsoleted first.  The 'NS32000' was
   multi-arched in 5.3 and then removed in 6.4, again without being
   obsoleted first.  Same thing with 'MCORE'.  Is this correct?

5) What is 'multi-arch'?  The 'set processor command can be used with
   PowerPC and the PowerPC 64-bit GDB can debug 64-bit or 32-bit 
   targets. (I have heard the latter refereed to as 'bi-arch').

GDB paper for GCC summit: New Commands

[PAUL GILLIAM]

Here is stuff about new commands I gleaned from NEWS.  I have some
questions at the end and would welcome any comments.  (I intend to do
new features separately from new commands and I know there will be some
overlap).


Feature: Checkpoints
  commands:
    checkpoint
    restart <n>
    info checkpoints
    delete-checkpoint <n>

Feature: fork
  commands:
    set|show detach-on-fork
    info forks
    fork <n>
    delete-fork <n>
    detach-fork <n>

Feature: Convenience variables
  commands:
    init-if-undefined

Feature: displaying arrays
  command:
    set print array-indexes

Feature: logging output to a file
  command:
    set|show logging

Other New Commands:
    start
    maint set profile on|off
    disconnect


Removed Commands:
  removed                         replacement
    set|show arm dissembly-favor  set|show arm disassembler
    othernames                    set arm disassembler
    set|show remotedebug          set|show debug remote
    set|show archdebug            set|show debug arch
    set|show eventdebug           set|show debug event
    regs                          info registers
    set prompt-escape-char        - none -
    

Qustions:
1) How do "set|show detach-on-fork" and "set|show follow-fork" work
   together? I think this is the answer:  If 'set detach-on-fork' is
   off, the 'set follow-fork' works as before.  If 'set detach-on-fork'
   is on, then the  state of 'set follow-fork' determines which for will
   be the 'current' fork.  Is this correct?

2) Does the new fork features also work with vfork?  If not, they are
   inconsistent with 'set|show follow-fork'.

3) If the name of the main procedure is 'main', is the start command
equivalent
   to 'tbreak main' followed by 'run', or is there something subtle
going on? 

Re: GDB paper accepted for GCC summit

[Randolph Chung]

> Removed configureations
> 	HP/PA running BSD		6.1

Since its removal, this configuration has been reintroduced. Mark
maintains this IIRC.

> 5) What is 'multi-arch'?  The 'set processor command can be used with
>    PowerPC and the PowerPC 64-bit GDB can debug 64-bit or 32-bit 
>    targets. (I have heard the latter refereed to as 'bi-arch').

This is my understanding:
multi-arch is a generalized form of biarch, the idea being that one gdb
binary can debug multiple targets. The most common form of this is a gdb
that can debug 32-bit and 64-bit binaries on the same machine, but
presumably one could build a gdb that can debug e.g. x86 targets
natively, and at the same time an embedded arm target. I don't know if
we are quite there yet though. Most of this work involves encapsulating
target specific operations into vectors that can be changed at runtime,
instead of having link-time bindings of those operations.

randolph

Re: GDB paper accepted for GCC summit

[Daniel Jacobowitz]

On Thu, Mar 30, 2006 at 09:26:53AM +0800, Randolph Chung wrote:
> This is my understanding:
> multi-arch is a generalized form of biarch, the idea being that one gdb
> binary can debug multiple targets. The most common form of this is a gdb
> that can debug 32-bit and 64-bit binaries on the same machine, but
> presumably one could build a gdb that can debug e.g. x86 targets
> natively, and at the same time an embedded arm target. I don't know if
> we are quite there yet though. Most of this work involves encapsulating
> target specific operations into vectors that can be changed at runtime,
> instead of having link-time bindings of those operations.

Yes.  We're very close; if someone wanted to make this work, they
probably could.  IIRC it once worked for a couple of embedded targets.

-- 
Daniel Jacobowitz
CodeSourcery

Re: GDB paper for GCC summit: New Commands

[Joel Brobecker]

> 3) If the name of the main procedure is 'main', is the start command
> equivalent to 'tbreak main' followed by 'run', or is there something
> subtle going on? 

Nothing subtle, it's exactly equivalent to "tbreak main; run".

-- 
Joel

Re: GDB paper accepted for GCC summit

[Mark Kettenis]

> From: Randolph Chung <tausq@debian.org>
> Date:  Thu, 30 Mar 2006 09:26:53 +0800
> 
> > Removed configureations
> > 	HP/PA running BSD		6.1
> 
> Since its removal, this configuration has been reintroduced. Mark
> maintains this IIRC.

Well, the configuration Paul mentions is for the old HP BSD.  I added
support for OpenBSD/hppa which is quite different.

Ah, and using HP/PA is a bit wierd.  The official name for the
architecture is PA-RISC, although the Open Source community seems to
use hppa to refer to the architecture.

Mark

Re: GDB paper for GCC summit: New Commands

[Eli Zaretskii]

> From: PAUL GILLIAM <pgilliam@us.ibm.com>
> Date: Wed, 29 Mar 2006 17:19:21 -0800
> 
> 1) How do "set|show detach-on-fork" and "set|show follow-fork" work
>    together?

Do you mean "set|show follow-fork-mode"?  If so, the answer is in the
manual (in the node "Processes"); if something there is unclear,
please tell what parts need to be clarified.

>                I think this is the answer:  If 'set detach-on-fork' is
>    off, the 'set follow-fork' works as before.  If 'set detach-on-fork'
>    is on, then the  state of 'set follow-fork' determines which for will
>    be the 'current' fork.  Is this correct?

I think it's the other way around: if detach-on-fork is ON, then "set
follow-fork" behaves as it did before: one of the two processes is
debugged bu GD, while the other runs unimpeded.  If it's OFF, then
both parent and the child are under GDB's control.

Again, I think this is stated quite clearly in the manual, so if
anything there sounds confusing, please identify the confusing parts.

> 2) Does the new fork features also work with vfork?

The text suggests that they do, but I don't know if this is correct as
a matter of fact.

> 3) If the name of the main procedure is 'main', is the start command
> equivalent
>    to 'tbreak main' followed by 'run', or is there something subtle
> going on? 

AFAIK, "start" is equivalent to "tbreak main; run".

GDB paper at GCC summit: user-level features

[PAUL GILLIAM]

Here is stuff about new or improved "user-level" features I gleaned from
NEWS.  I will try non-user level features next.  I would welcome any
comments.

--------  >6.4  --------

New Features:

    Checkpoints
This facility allows the user to create a checkpoint, continue
        debugging, and then 'backup' to the point where the checkpoint
        was taken.  More that one checkpoint can be made and commands
        have been added to manage them.

Improved Features:

    fork
Previously, the user had to decide which process should continue
        to be debugged after a fork: the parent or the child.  The one
        not debugged would run unhindered to completion.  Now it is 
        possible to debug both processes without the kludge of starting
        a second GDB.

    Convenience Variables
A number of improvements where made for convenience variables:
        *  A new command was added: "init-if-undefined": this is useful
           for user defined functions that need to save state.
        *  In general, convenience variables are no longer reset by a
           symbol-file command.

    Windows Host Support
GDB now builds as a cross debugger hosted on i686-mingw32,
        including native console support, and remote communications
        using either network sockets or serial ports.

Removed Features:

    ARM rdi-share module

    Netware NLM Debug Server


--------  6.4  --------

New Features:

    BSD user-level threads support
User level thread libraries are now supported for freeBSD and
        openBSD.  Kernel thread libraries are not yet supported.

    VAX floating point support
Support was added for the not-quite-IEEE VAX F and D floating
        point formats.

Improved Features:

    User-defined command support   
        A new convenience variable, $argc, has been added so that a user
        defined function can know how man arguments were given when it
        is invoked.

    Displaying Arrays
When an array is displayed, its values are displayed without
        reference to their index in the array.  The new 'set  print 
        array-indexes" command my be used so that index values are
        included.

Removed Features:



--------  6.3  --------

New Features:

    "-l" command line option 
        GDB now accepts -l followed by a number to set the timeout for
        remote debugging.

    Support for GCC -feliminate-dwarf2-dups
        GDB now supports a more compact representation of DWARF-2 debug
        information using DW_FORM_ref_addr references.  These are
        produced by GCC with the option -feliminate-dwarf2-dups and also
        by some proprietary compilers.  With GCC, you must use GCC 3.3.4
        or later to use -feliminate-dwarf2-dups.

    Internationalization
        When supported by the host system, GDB will be built with
        internationalization (libintl).  The task of marking up the
        sources is continued, we're looking forward to our first
        translation.

    Ada
        Initial support for debugging programs compiled with the GNAT
        implementation of the Ada programming language has been
        integrated into GDB.  In this release, support is limited to
        expression evaluation.

Improved Features:

    Remote Protocol
        GDB's remote protocol now includes support for the 'p' packet.
        This packet is used to fetch individual registers from a remote
        inferior.

Removed Features:



--------  6.2.1  --------

This release fixed a couple of near 'show stoppers' on the MIPS and VAX
architectures.


--------  6.2 --------

New Features:

    Support for the BSD Kernel Data Access Library (libkvm) interface.
        Using 'target kvm', it is now possible to debug kernel core
        dumps and live kernel memory images on various BSD flavored 
        platforms.  Currently, the following native-only configurations
        are supported:  FreeBSD/amd64, FreeBSD/i386, NetBSD/i386,
        NetBSD/m68k, NetBSD/sparc, OpenBSD/amd64, OpenBSD/i386,
        OpenBSD/m68k, and OpenBSD/sparc.

    Cygwin support for DWARF 2.

Improved Features:

    Threads
        Support for NPTL threads was enhanced to work better with target
        programs that rapidly create and delete threads.

Removed Features:

    Command line options "-async" and "-noasync", which supported the
    broken "no acync" feature, where removed, effectively removing the
    feature.



--------  6.1.1  --------

This was primarily a maintenance release to fix several built problems.

New Features:

Improved Features:

    Text-mode User Interface
        The TUI (text-mode user interface) is now build by default.
        This is a curses based interface that provides a kind of
        primitive 'GUI' and can be activated by using the -i=tui command
        line option to GDB or by running the separate "gdbtui" program.
        See the manual for more info.

Removed Features:



--------  6.1  --------

New Features:

    Pending Breakpoints
        Support was added to allow setting breakpoints in shared
        libraries that have not yet been loaded.  If the 'breakpoint
        pending' option is set to auto, the user is asked if a the
        breakpoint should be made pending on a future shared-library
        load.  When the breakpoint symbol is resolved, the pending
        breakpoint is removed and one or more regular breakpoints are
        created.  Pending breakpoints are very useful for GCJ Java
        debugging.

Improved Features:

    New C++ Demangler
        A new demangler was added that does a better job on mangled
        names generated by G++.  The new demangler also runs faster,
        helping GDB to start up faster on large C++ programs.

    DWARF 2 Location Expressions
        Support was extended to support function arguments and frame
        bases.  Formally, these would cause GDB to crash.

    C++ nested types and namespaces
        Support for these was improved, especially for users of DWARF 2.

Removed Features:



--------  6.0  --------

New Features:

    Objective-C
        Support for debugging programs written in the Objective-C
        language has been integrated into GDB.

    Thread local storage (TLS)
	Now supports the GNU/Linux implementation of per-thread
        variables.

Improved Features:
    Threads
	GDB now supports the new NPTL threads as well as the older
        LinuxThreads library.

Removed Features:

Re: GDB paper accepted for GCC summit

[PAUL GILLIAM]

Here is stuff about new or improved "user-level" features I gleaned from
NEWS.  I would welcome any comments.

--------  >6.4  --------

New Features:

    Checkpoints
This facility allows the user to create a checkpoint, continue
        debugging, and then 'backup' to the point where the checkpoint
        was taken.  More that one checkpoint can be made and commands
        have been added to manage them.

Improved Features:

    fork
Previously, the user had to decide which process should continue
        to be debugged after a fork: the parent or the child.  The one
        not debugged would run unhindered to completion.  Now it is 
        possible to debug both processes without the kludge of starting
        a second GDB.

    Convenience Variables
A number of improvements where made for convenience variables:
        *  A new command was added: "init-if-undefined": this is useful
           for user defined functions that need to save state.
        *  In general, convenience variables are no longer reset by a
           symbol-file command.

    Windows Host Support
GDB now builds as a cross debugger hosted on i686-mingw32,
        including native console support, and remote communications
        using either network sockets or serial ports.

Removed Features:

    ARM rdi-share module

    Netware NLM Debug Server


--------  6.4  --------

New Features:

    BSD user-level threads support
User level thread libraries are now supported for freeBSD and
        openBSD.  Kernel thread libraries are not yet supported.

    VAX floating point support
Support was added for the not-quite-IEEE VAX F and D floating
        point formats.

Improved Features:

    User-defined command support   
        A new convenience variable, $argc, has been added so that a user
        defined function can know how man arguments were given when it
        is invoked.

    Displaying Arrays
When an array is displayed, its values are displayed without
        reference to their index in the array.  The new 'set  print 
        array-indexes" command my be used so that index values are
        included.

Removed Features:



--------  6.3  --------

New Features:

    "-l" command line option 
        GDB now accepts -l followed by a number to set the timeout for
        remote debugging.

    Support for GCC -feliminate-dwarf2-dups
        GDB now supports a more compact representation of DWARF-2 debug
        information using DW_FORM_ref_addr references.  These are
        produced by GCC with the option -feliminate-dwarf2-dups and also
        by some proprietary compilers.  With GCC, you must use GCC 3.3.4
        or later to use -feliminate-dwarf2-dups.

    Internationalization
        When supported by the host system, GDB will be built with
        internationalization (libintl).  The task of marking up the
        sources is continued, we're looking forward to our first
        translation.

    Ada
        Initial support for debugging programs compiled with the GNAT
        implementation of the Ada programming language has been
        integrated into GDB.  In this release, support is limited to
        expression evaluation.

Improved Features:

    Remote Protocol
        GDB's remote protocol now includes support for the 'p' packet.
        This packet is used to fetch individual registers from a remote
        inferior.

Removed Features:



--------  6.2.1  --------

This release fixed a couple of near 'show stoppers' on the MIPS and VAX
architectures.


--------  6.2 --------

New Features:

    Support for the BSD Kernel Data Access Library (libkvm) interface.
        Using 'target kvm', it is now possible to debug kernel core
        dumps and live kernel memory images on various BSD flavored 
        platforms.  Currently, the following native-only configurations
        are supported:  FreeBSD/amd64, FreeBSD/i386, NetBSD/i386,
        NetBSD/m68k, NetBSD/sparc, OpenBSD/amd64, OpenBSD/i386,
        OpenBSD/m68k, and OpenBSD/sparc.

    Cygwin support for DWARF 2.

Improved Features:

    Threads
        Support for NPTL threads was enhanced to work better with target
        programs that rapidly create and delete threads.

Removed Features:

    Command line options "-async" and "-noasync", which supported the
    broken "no acync" feature, where removed, effectively removing the
    feature.



--------  6.1.1  --------

This was primarily a maintenance release to fix several built problems.

New Features:

Improved Features:

    Text-mode User Interface
        The TUI (text-mode user interface) is now build by default.
        This is a curses based interface that provides a kind of
        primitive 'GUI' and can be activated by using the -i=tui command
        line option to GDB or by running the separate "gdbtui" program.
        See the manual for more info.

Removed Features:



--------  6.1  --------

New Features:

    Pending Breakpoints
        Support was added to allow setting breakpoints in shared
        libraries that have not yet been loaded.  If the 'breakpoint
        pending' option is set to auto, the user is asked if a the
        breakpoint should be made pending on a future shared-library
        load.  When the breakpoint symbol is resolved, the pending
        breakpoint is removed and one or more regular breakpoints are
        created.  Pending breakpoints are very useful for GCJ Java
        debugging.

Improved Features:

    New C++ Demangler
        A new demangler was added that does a better job on mangled
        names generated by G++.  The new demangler also runs faster,
        helping GDB to start up faster on large C++ programs.

    DWARF 2 Location Expressions
        Support was extended to support function arguments and frame
        bases.  Formally, these would cause GDB to crash.

    C++ nested types and namespaces
        Support for these was improved, especially for users of DWARF 2.

Removed Features:



--------  6.0  --------

New Features:

    Objective-C
        Support for debugging programs written in the Objective-C
        language has been integrated into GDB.

    Thread local storage (TLS)
Now supports the GNU/Linux implementation of per-thread
        variables.

    Dwarf 2 location expressions
These allow a compiler to more completely describe where
        variables are located, in memory and/or registers, even when
        optimization is used.  Preliminary support was a added


Improved Features:

    Remote Protocol
Extended to support hosted file I/O.  This is  where the remote
        target can make use of the file system that GDB can access.

    Threads
GDB now supports the new NPTL threads as well as the older
        LinuxThreads library.

Removed Features: