[lldb-dev] Increasing support for other gdbservers

[Vince Harron]

This is a pretty cool feature for people who want to use lldb on windows
against gdbserver


On Tue, Mar 31, 2015 at 5:57 PM, Zachary Turner <zturner at google.com> wrote:

> I think uses of it would only need to be guarded if we plan to use it in
> generic code. So yea, if all the code that uses it goes into a file that
> isn't compiled on windows anyway, then the problem becomes very simple
> On Tue, Mar 31, 2015 at 5:41 PM Jason Molenda <jmolenda at apple.com> wrote:
>
>> fwiw on Mac OS X we use libxml2 over in Plugins/SymbolVendor/MacOSX/SymbolVendorMacOSX.cpp.
>> That plugin's initialization is #ifdef __APPLE__ over in
>> SystemInitializerFull.cpp; we don't have ifdef guard around the use of
>> libxml2 in SymbolVendorMacOSX itself.
>>
>>
>> > On Mar 31, 2015, at 4:18 PM, Vince Harron <vince at nethacker.com> wrote:
>> >
>> > I really don't want LLDB to embed a copy of libxml2.  I think we should
>> build it externally and reference it from LLDB.  Systems with package
>> managers can get this trivially.  Windows can download and build all
>> dependencies with one script.
>> >
>> > On Mar 31, 2015 2:10 PM, "Colin Riley" <colin at codeplay.com> wrote:
>> > I noticed that use in cmake also. FWIW, my primary LLDB platform is
>> Windows, which is why we were using TinyXML2 for ease of prototyping. If
>> libxml2 works on all the targets we will use it - I do worry about the
>> usual issues you get with windows prebuilts. So source may still be
>> required. We'll look into it.
>> >
>> > Colin
>> >
>> > On 31/03/2015 20:45, Zachary Turner wrote:
>> >> There's already some stuff in the CMake to try to find libxml, but
>> it's behind a Darwin specific branch in the CMake.  So I think what would
>> need to happen is that we move this into a platform agnostic codepath, and
>> then set a define like LLDB_HAVE_LIBXML2 in the code to a value that
>> indicates whether it is present (search clang for CLANG_HAVE_LIBXML in *.*
>> to see how this is done).  Then, in the code, we would need to put xml code
>> behind a check for this define.
>> >>
>> >> On Tue, Mar 31, 2015 at 10:02 AM Zachary Turner <zturner at google.com>
>> wrote:
>> >> A good rule of thumb for anything is that "Windows doesn't have it"
>> and that holds true for libxml2 as well.  It appears that libxml2 does
>> support Windows though (http://xmlsoft.org/downloads.html), it just
>> isn't something that's there by default.  It would be nice if everyone were
>> using the same thing, could we clone this repo in our own repo and then
>> just build it ourselves as part of the build process.  The license looks
>> very permissive, but IANAL.
>> >>
>> >> On Tue, Mar 31, 2015 at 9:47 AM Greg Clayton <gclayton at apple.com>
>> wrote:
>> >>
>> >> > On Mar 31, 2015, at 3:35 AM, Aidan Dodds <aidan at codeplay.com> wrote:
>> >> >
>> >> > On 30/03/2015 18:38, Greg Clayton wrote:
>> >> > >
>> >> > > I know about the register numbering stuff and I would love to see
>> support for the "$qXfer:features:" added to LLDB. The one thing this data
>> doesn't contain is the register numbers for the ABI (DWARF register numbers
>> (for debug info), compiler register numbers (for like .eh_frame)), but that
>> info could be inferred from an ABI plugin that we could infer from the
>> "osabi" of "GNU/Linux" in the target.xml:
>> >> >
>> >> > >
>> >> > > So please do submit patches that implement this and we will be
>> happy to approve them.
>> >> >
>> >> > I am currently prototyping $qXfer:features support in LLDB with an
>> aim to upstream it. It will require an XML parser, so I wanted to have a
>> discussion about adding one to LLDB.
>> >>
>> >> Most unix variants have libxml2 that is available. I am not sure on
>> windows though. I have CC'ed Zachary to get some input on windows XML (in
>> case LLVM doesn't already have some support for this).
>> >>
>> >> > I have been using TinyXML2 in my prototype, which is open sourced
>> under the ZLib license. Is there any policy in LLDB for handling external
>> library dependencies?
>> >> > Would there be objections to TinyXML2 making its way into the LLDB
>> code base as an external? Writing a new XML parser from scratch in LLDB
>> isn't ideal.
>> >>
>> >> It would be great to stick with stuff that everyone has installed and
>> hopefully that is libxml2. Windows is the biggest question. I am also not
>> sure if llvm or clang has any XML support, but we should first look to see
>> if llvm has XML support and if not, then look for alternatives. We
>> definitely do not want to write our own.
>> >> >
>> >> > I would still like to have a discussion about adding a plugin
>> architecture to gdb-remote making it easier to handle packets outwith the
>> LLDB based servers. The code in gdb-remote that sends and handles packets
>> is scattered over one or two huge classes, it would be beneficial to start
>> looking at breaking this up and modularizing it. At least for the packets
>> which are not supported by lldb's own RSP producers.
>> >>
>> >> I say just build all and any support it into
>> GDBRemoteCommunicationClient and GDBRemoteCommunicationServer. I don't see
>> the need to break it up.
>> >>
>> >> Greg Clayton
>> >>
>> >>
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