I like the JSON approach. We might need to include the mangled name for the
function or specify where arguments go if we aren't going to expect a canned
function to be in each dylib. That is a bit harder, but something we should
think about.
If we look at __cxa_demangle:
char* abi::__cxa_demangle(const char *mangled_name, char *output_buffer, size_t
*length, int *status);
I am not sure how we would logically specify this in the JSON... Where to put
the name to demangle, how to call it etc...
> On Sep 22, 2016, at 9:56 AM, Timothee Cour <timothee.co...@gmail.com> wrote:
>
>
>
> On Wed, Sep 21, 2016 at 4:13 PM, Greg Clayton via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
> You could have a setting that allows you to specify prefix as the key with a
> dylib path as a value. Would you expect a function with certain name or would
> you need to specify the function name (probably mangled) as well? Let me know
> what you are thinking?
>
>
> whatever works it doesn't really matter so long there's something to get
> started, I was going for something simple to start with but if you want this
> level of flexibility how about using a json config file:
>
> export LLDB_DEMANGLE_CONFIG_FILE="~/.lldbl.demangle.conf"
>
> cat ~/.lldbl.demangle.conf
>
> {"demangle":
> ["D": {"prefix" : "_D", "shared_libary_file" : "/path/libdemangled.dylib",
> "mangled_name", "_demangle_custom_D"}],
> ["nim": /* same for nim language */ ],
> }
>
> Greg
>
> > On Sep 21, 2016, at 3:50 PM, Timothee Cour <timothee.co...@gmail.com> wrote:
> >
> >
> >
> > On Wed, Sep 21, 2016 at 3:35 PM, Greg Clayton via lldb-dev
> > <lldb-dev@lists.llvm.org> wrote:
> > Sounds like you could then make a setting that is a dictionary where you
> > say what the prefix is (like maybe "_D") and the value is the path to the
> > tool to use? This would be easy to implement. Demangling does tend to be
> > one of the most expensive parts of symbol file and debug info parsing, so
> > if you do this, you will want to make sure the shell tool can be spawned
> > and kept running maybe?
> >
> > Greg
> >
> >
> > where in the lldb code would be such entry point?
> >
> > instead of a binary it can just be a library dynamically loaded via dlopen
> > (as i wrote, though I should've called it LLDB_DEMANGLER_LIB instead of
> > LLDB_DEMANGLER_EXE), and the dynamically loaded symbol be cached to make
> > sure it's dlopen'd at most once per process.
> >
> > Then it's easy enough for us to write a demangleCustom that is fast on the
> > D side of things. It can also work with a binary instead of a dllib but
> > would be a bit slower (could have a client server model, but that's more
> > complex than the simple dllib solution i was proposing).
> >
> > yes, we could use a prefix for that as well.
> >
> >
> > > On Sep 21, 2016, at 3:30 PM, Timothee Cour <timothee.co...@gmail.com>
> > > wrote:
> > >
> > >
> > >
> > > On Wed, Sep 21, 2016 at 3:10 PM, Greg Clayton <gclay...@apple.com> wrote:
> > > There is no external demangling plug-in infrastructure at the moment, but
> > > you could add functionality that would allow it. No one is going to have
> > > D installed by default. Where do you expect your demangler dylib to live?
> > > Would you just add code that tries to locate the dylib in N places on the
> > > current system and try to dlopen it? Avoiding duplication and just not
> > > having the functionality at all unless something else is might not make
> > > it that useful. Is D stable? Is the mangling changing at all? Will you
> > > require a demangler to be vended with each new version of the tool? Are
> > > all previous demanglings still valid in newer versions? Can you figure
> > > out the version of the D from a compiled executable so that you might be
> > > able to locate one of 5 different installs of D and select the right one?
> > > Let me know what you use case is.
> > >
> > > Greg
> > >
> > >
> > > one simple flexible backward compatible option would be to have a generic
> > > environment variable:
> > >
> > > ```
> > > export LLDB_DEMANGLER_EXE="/usr/bin/ddemangle"
> > > lldb myprog
> > > ```
> > >
> > > inside lldb (D-like pseudo code):
> > >
> > > ```
> > > bool demangle(string symbol, string* output){
> > > auto path=env["LLDB_DEMANGLER_EXE"];
> > > if(!path.empty) {
> > > auto demangleCustom=cast(proper_type) dlopen(path);
> > > if(demangleCustom(symbol, output)) return true;
> > > // fallsback to default code if custom code didn't handle symbol
> > > }
> > > return run_default_lldb_demangle(symbol, output);
> > > }
> > > ```
> > >
> > > user defined demangler (eg D's demangler)
> > > ```
> > > // return true if can demangle symbol (ie it's a D symbol in our case)
> > > bool demangleCustom(string symbol, string* output);
> > >
> > > ```
> > >
> > > >> Is the mangling changing at all?
> > >
> > > yes, there's some ongoing work on making the mangling scheme produce much
> > > shorter symbols. The logic is complex, and it'd be a lot of work to
> > > reproduce this.
> > >
> > > Bottomline: this scheme is very flexible, and it'd be no less useful than
> > > current situation, where lldb just returns the symbol unchanged if it
> > > can't demangle.
> > >
> > >
> > >
> > >
> > > > On Sep 21, 2016, at 3:00 PM, Timothee Cour <thelastmamm...@gmail.com>
> > > > wrote:
> > > >
> > > > Is there a way to provide a hook (eg, via an extern(C) function, or
> > > > using a dynamically loaded shared library) to do this, so as to simply
> > > > reuse D's https://dlang.org/phobos/std_demangle.html and make sure it's
> > > > always in sync with D's demangling instead of duplicating code
> > > >
> > > > On Wed, Sep 21, 2016 at 10:24 AM, Greg Clayton via lldb-dev
> > > > <lldb-dev@lists.llvm.org> wrote:
> > > > It might be nice to add demangling support to llvm and then use it by
> > > > modifying "Mangled::GetDemangledName()" in Mangled.cpp. This is where
> > > > all demangling happens. Hopefully you have a great prefix that won't
> > > > conflict with other languages "_Z" for C++, "_T" for swift. But the
> > > > code in Mangled::GetDemangledName() will look at the prefix and attempt
> > > > to demangle the name based on what prefix it starts with.
> > > >
> > > >
> > > > > On Sep 21, 2016, at 5:52 AM, Johan Engelen via lldb-dev
> > > > > <lldb-dev@lists.llvm.org> wrote:
> > > > >
> > > > > Hi all,
> > > > > I recently looked into adding demangling support for D in LLDB, but
> > > > > got lost in the code.
> > > > > (right now, basic D support is there with:
> > > > > https://reviews.llvm.org/D24794)
> > > > >
> > > > > I'd like some pointers to where demangling is done for the other
> > > > > languages, and to where I should add D support for it.
> > > > >
> > > > > Thanks a lot,
> > > > > Johan
> > > > >
> > > > > _______________________________________________
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> > > >
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> > > >
> > >
> > >
> >
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> >
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