[LLVMdev] C++ demangling in LLVM

[Chandler Carruth]

In the same way that the core LLVM libraries have support routines for
DWARF, I think that both mangling and demangling should be provided as
well. I suspect that the 'Support' library is the best we have, although
eventually we need to split this library up a bit. That's not really your
problem though.

The bigger problem is that we don't have any good way of sharing code
between runtime libraries (such as libcxxabi, sanitizer runtimes, etc) and
LLVM.

One somewhat interesting question, would the APIs exposed by libcxxabi be
sufficient for the sanitizer runtimes?

AFAICT, the only other way forward is to:

1) Move/re-implement the demangling (and hopefully the mangling as well)
into llvm/Support, following proper style and writing proper unittests as
we go.
2) Write my object-file-scrubber so that we can statically link
llvm/Support into a runtime without collision issues.
3) Potentially split up llvm/Support (and other libraries) enough to have
depending upon it not burden or bloat the runtime libraries unnecessarily.


All of these options seem... moderately painful. My inclination is to start
paving the way for better code sharing in runtime libraries sooner rather
than later. Other thoughts? Chris?


On Wed, Jul 4, 2012 at 9:53 PM, Alexey Samsonov <samsonov at google.com> wrote:

>
>
> On Wed, Jul 4, 2012 at 11:43 PM, Michael Spencer <bigcheesegs at gmail.com>wrote:
>
>> On Wed, Jul 4, 2012 at 8:33 AM, Alexey Samsonov <samsonov at google.com>
>> wrote:
>> > Hello!
>> >
>> > We want to implement in-process symbolizer for {Address,Thread}Sanitizer
>> > testing tools that would be based on LLVM libraries.
>> > I've noticed that llvm-nm (as well as other tools) doesn't demangle C++
>> > names. Is it true, that LLVM doesn't have the code that is capable
>> > of that, and if yes, are there any plans to add it?
>> > Depending on something like libiberty.a doesn't seem like a good or
>> portable
>> > solution.
>> >
>> > --
>> > Alexey Samsonov, MSK
>> >
>>
>> Yes, LLVM currently has no C++ demangler, and it needs one. Although I
>> have no idea where it should live. It would be nice if it could live
>> in clang next to the mangler, but clang doesn't even need a demangler.
>> llvm tools, lld, and compiler-rt do.
>
>
> llvm/Support?
>
> It's not that clear how libcxxabi could be used in llvm tools, as IIUC
> this library is built independently.
> The demangler implementation there is 10 KLOC which are rather far from
> LLVM style.
>
> --
> Alexey Samsonov, MSK
>
>
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