[LLVMdev] unwind's permanent residence

[Nick Kledzik]

I thought the ARM EHABI added a twist to this because it created some upward dependency from the unwinder to libc++abi.

Other than that, I don’t have any strong feeling where it lives.

-Nick

On Jan 30, 2015, at 12:33 PM, Renato Golin <renato.golin at linaro.org> wrote:
> On 30 January 2015 at 20:17, Saleem Abdulrasool <compnerd at compnerd.org> wrote:
>> There is a valid point that the
>> unwinder supports the compiler in some sense (for exception handling).  It
>> seems that its not particularly as intrinsically tied to the compiler as the
>> builtins are.
> 
> Unwinding is not just used for EH, but also debugging, profiling,
> sanitizers (when in slow-mode) and possibly other code inspection
> tools. While still not strictly for *compiler* support, it is for many
> other toolchain components.
> 
> The counter argument, that libc++ has other low-level code to deal
> with exception handling so it would make sense to bundle the unwinder
> together, is also compelling. But in my view, less so.
> 
> 
>> So, I am bringing up this question once more: what can we do about this
>> concern?  Is moving it to a separate repository acceptable?  Or perhaps
>> moving it to compiler-rt is palatable to more of the involved developers (as
>> much as I may prefer an alternate solution).
> 
> For my purposes, bundling it in compiler-rt would be the easiest
> solution. It'd also make Clang simpler regarding --rtlib=compiler-rt.
> I'm also assuming that libc++ should be able to work with libgcc_s and
> other unwinding libraries, and, even if our unwinder is local to it,
> it seems very standard in the interface it exports.
> 
> However, if libc++ folks don't want to depend on compiler-rt or
> libgcc_s for their own unwinding, I don't see a problem in having it
> in a separate repository under the LLVM server. One less, one more,
> won't make a difference for developers and build systems.
> 
> What I don't agree is to leave it as it is, so that even to compile C
> code in debug/profile mode, I need to either include libgcc_s or
> libc++abi.
> 
> cheers,
> --renato