[llvm-dev] (Thin)LTO llvm build

[Carsten Mattner via llvm-dev]

On Wed, Dec 21, 2016 at 2:55 PM, Teresa Johnson <tejohnson at google.com> wrote:
> I think you can get this via "ninja -t commands bin/lldb-argdumper"
> (this will give you a lot of output, all of the compilation commands
> used to build that target). Or redo the build with -v to be sure.

Unfortunately the old build tree is gone for space reclaim reasons. Sorry,
I'll make sure to not nuke it the next time. I guess I thought the detailed
error message would be enough.

I didn't build again, but I did configure with the settings posted yesterday,
and there's a warning which I'm unsure how to interpret and if it's a
concern:

---
CMake Warning at tools/lldb/cmake/modules/LLDBConfig.cmake:409 (message):
  You appear to be linking to libstdc++ version lesser than 4.9 without
  exceptions enabled.  These versions of the library have an issue, which
  causes occasional lldb crashes.  See
  <https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59656> for details.  Possible
  courses of action are:

  - use libstdc++ version 4.9 or newer

  - use libc++ (via LLVM_ENABLE_LIBCXX)

  - enable exceptions (via LLVM_ENABLE_EH)

  - ignore this warning and accept occasional instability
Call Stack (most recent call first):
  tools/lldb/CMakeLists.txt:4 (include)
---

libstdc++ is 6.2.1 so the CMake check seems wrong.

This prompted me to use -libstd=libc++ and -DLLVM_ENABLE_LIBCXX=ON,
but for some reason Arch Linux packages llvm and clang in version 3.9.0
but libc++ in 3.8.0, so I skipped it.

Unless the above libstdc++ warning is a problem, I will build and report
back when done.