[LLVMdev] unwind's permanent residence

[Jonathan Roelofs]

On 2/3/15 5:07 AM, Renato Golin wrote:
> On 30 January 2015 at 20:43, Jonathan Roelofs <jonathan at codesourcery.com> wrote:
>> Last time we brought this up, there was only partial consensus, and then
>> someone arbitrarily declared total consensus (without compelling arguments
>> in any particular direction) that we were going to move it to compiler_rt.
>> Then the discussion fell on the floor because no-one had time to actually do
>> the move. Please, let's not let that happen again this time.
>
> So, do we have a consensus?
Wheeee Two Generals problem...
>
> AFAICS, the most agree solution (with optionals to be defined):
>
> 1. Move Unwinder to its own repository in the LLVM server
      1.1 Freeze the code
      1.2 Copy unwinder to its own repo
      1.3 Migrate all the buildbots that care about libc++abi's unwinder
      1.4 Delete the old copy
      1.5 Unfreeze the code
> 2. Make the CMake connections from libc++abi and compiler-rt
>    2.1 OPTIONAL 1: err if libunwinder is not there, clang errs if rtlib=RT
>    2.2 OPTIONAL 2: warns if libunwind is not there, clang errs if rtlib=RT
>    2.3 OPTIONAL 3: nothing, make clang smarter to pick existing unwinder
> 3. Change clang to assume -lunwind when --rtlib=compiler-rt
>    3.1 OPTIONAL 4: allow linker error if no -lunwind / -lgcc_s
>    3.2 OPTIONAL 5: Add option to change unwinder library by not adding
> -lunwind/-lgcc_s, but whatever comes as argument
>
> 1, 2, and 3 must be changed.
>
> I vote for adding { 2.2, 3.1 } for now, { 2.2, 3.1, 3.2 } for later.
+1
>
> My idea for 3.2 is something like --unwinder=libgcc_s / libunwind, or
> something like that.
>
> I personally don't think the front-end scanning existing libraries is
> a good thing to do,
Agreed.
> but I'm not against the idea, if anyone feels
> strongly about it.
>
> If all of us could agree to a common solution, and make sure all
> interested parties are in, we should do the move before 3.7.
+1
>
> Please, cast your votes.
>
> cheers,
> --renato
>

-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded