[lldb-dev] Proposal: Using LLD in tests

Greg Clayton via lldb-dev lldb-dev at lists.llvm.org
Thu Apr 19 09:24:27 PDT 2018

The last I knew LLD doesn't work on mach-o very well, so be sure to not require LLD for linking any Darwin executables.

> On Apr 19, 2018, at 6:42 AM, Pavel Labath via lldb-dev <lldb-dev at lists.llvm.org> wrote:
> Hello all,
> currently we have a couple of tests, in-tree or under review, which are
> very close to being host-independent. The only part they are missing is the
> ability to link a intermediate object file:
> - the ppc64 test in https://reviews.llvm.org/D44437 needs a linker to
> resolve relocations in the debug info (*)
> - the PDB tests under lit/SymbolFile/PDB need a linker to produce the
> program database.
> I think it would be great if everyone were able to run these tests and
> verify they don't regress them before they actually push a patch.
> Apart from that, I have started looking at writing some non-execution debug
> info (**) tests as a part of adding DWARF v5 accelerator table support to
> lldb (both to test the new implementation, and to make sure I don't regress
> existing ones). Ideally I'd like to make sure that everyone is able to run
> them, regardless of their primary (or only) development platform. For this,
> I also need a linker capable of running everywhere (*)
> To achieve these goals, I'd like to propose that we add LLD as a (optional,
> but strongly recommended) dependency for running tests and start using it
> in the tests I mention. Doing this would optional in the sense that the
> tests would be marked "REQUIRED: lld", and simply skipped if lld is not
> available (so the tests would still be green). I say "strongly recommended"
> because not having lld checked out should not be an excuse for breaking the
> test, and the patch author should pro-actively revert a patch which breaks
> such tests and investigate.
> I hope this proposal is not too controversial. LLD is already required on
> windows to run dotest tests. Also, all monorepo users likely have it
> already, or it is very easy for them to enable it. For non-monorepo users
> it should be a matter of checking out one extra repository. Please Let me
> know what you think.
> pavel
> (*) our ELF parser has very limited support for applying debug info
> relocations -- it only works for x86, and only a couple of relocations are
> currently implemented. It would be possible to remove the linker dependency
> by implementing these (essentially, doing the link ourselves -- this is
> what llvm does), but given the large number of architectures and relocation
> types, combined with the long term goal of reusing the llvm's ELF parser,
> this does not seem like a worthwhile goal. Also, it does not help the
> windows situation, as in the PDB model it's the linker who produces the
> pdb's.
> (**) I'll write a separate email about this, but what I'm essentially
> thinking of is producing a stand-alone module (either from .yaml, .s, .ll,
> or .c), hitting it with various FindXXX methods, and dumping the results.
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