[PATCH] D20083: Add an c++ itanium demangler to llvm

[Craig, Ben via llvm-commits]

On 8/24/2016 1:20 PM, Rafael Espíndola wrote:
>
> We need a demangler in llvm, and that requires annoying tradeoffs:
>
> * llvm depends on libc++abi.
> * libc++abi depends on llvm.
> * both llvm and libc++abi dependent on a libdemangle.
> * we keep a file in both repositories.
> * we have two independent implementations.
>
> The first 3 introduce annoying dependencies. The last one means the 
> llvm demangler can have a nice interface (stringref), but duplicates a 
> lot of code.
>
> Having a file that is copied in both repositories is the least 
> horrible option IMHO. Having said that, any solution where lld on 
> windows can demangle itanium  names would work for us.
>
I agree that duplication isn't ideal.  I also agree that it's probably 
the best option here.  I think option 4 naturally turns into option 5 
over time, and in this situation, I think that is also fine (though 
annoying).

> Cheers,
> Rafael
>
>
> On Aug 24, 2016 1:16 PM, "Mehdi Amini" <mehdi.amini at apple.com 
> <mailto:mehdi.amini at apple.com>> wrote:
>
>
>     > On Aug 24, 2016, at 9:56 AM, Craig, Ben
>     <ben.craig at codeaurora.org <mailto:ben.craig at codeaurora.org>> wrote:
>     >
>     > On 8/24/2016 11:31 AM, Rafael Espíndola wrote:
>     >>> 1. I think there are already too many build time dependencies
>     crossing the compiler / runtime boundary. I'm tired of my libcxx
>     and libcxxabi builds failing because of unrelated cmake changes in
>     LLVM.  To avoid that, I could build a standalone version... but
>     now that won't be easily possible because of this change.
>     >> Not sure I follow. Note that this function is in an independent
>     >> library with no dependencies.
>     >>
>     >>> Building libcxx and libcxxabi shouldn't require me to pull
>     down llvm sources, or to have a "dev" install of llvm, and this
>     change makes that problem even worse than it already is.  Will
>     this even work for the cross compilation cases?
>     >> This should not change this case at all. This just adds a file
>     to llvm
>     >> itself. In a future change I will add a ifdef to it so that it can
>     >> also be used with no changes in libcxxabi.
>     > I guess I'm protesting the future change, rather than this
>     change. libc++abi should not use source files, header files,
>     static libraries, or shared objects that come from the llvm
>     repository.
>
>     That's bothering: it means that any functionality has to be
>     reimplemented (can’t use simple StringRef or Twine helper, which
>     is annoying when doing string processing like here).
>
>     —
>     Mehdi
>

-- 
Employee of Qualcomm Innovation Center, Inc.
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum, a Linux Foundation Collaborative Project

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