[llvm-dev] moving libfuzzer to compiler-rt?

[George Karpenkov via llvm-dev]

>From my understanding, the entire file `compiler-rt/cmake/modules/CompileRTCompile.cmake` is dedicated to using the trick
of using the just-built-compiler for compiling the sources.
Copying it seems suboptimal.
I can move it to `llvm/cmake/modules`, but that would be one step away from the ability to built `compiler-rt` without the parent repository.
Should that matter?

> not build at all

Why not? libfuzzer itself does not require instrumentation (at least from my understanding),
the actual problem arises with tests.

> On May 2, 2017, at 9:34 PM, Justin Bogner via llvm-dev <llvm-dev at lists.llvm.org> wrote:
> 
> Reid Kleckner via llvm-dev <llvm-dev at lists.llvm.org> writes:
>> On Tue, May 2, 2017 at 4:28 PM, Kostya Serebryany via llvm-dev <
>> llvm-dev at lists.llvm.org> wrote:
>> 
>>> On Tue, May 2, 2017 at 12:26 PM, George Karpenkov <ekarpenkov at apple.com>
>>> wrote:
>>> 
>>>> From my understanding, all these problems can be solved entirely
>>>> 
>>> by moving libfuzzer to compiler-rt, where (other) sanitizers already
>>>> reside.
>>>> 
>>> 
>>> Yes, that might be a reasonable thing to do.
>>> I am trying to remember the reasons why we've put libFuzzer into llvm and
>>> not into compiler-rt in the first place, and failing to do so.
>>> 
>> 
>> IIRC you thought libFuzzer would be more tightly coupled to LLVM
>> instrumentation, so the goal was to reap monorepo-like productivity
>> developments without waiting for it to happen?
>> 
>> Maybe it was a licensing concern, UIUC vs dual UIUC/MIT?
>> 
>> 
>>> Any thoughts on the suggestion?
>>>> 
>>>> It would be still possible to compile just libfuzzer with no
>>>> dependencies, by simply making a partial checkout from SVN,
>>>> and only the repo path would change.
>>>> 
>>> 
>>> This would cause some annoyance for me and maybe some users, but nothing
>>> we can't tolerate.
>>> Still what are our other options?
>>> 
>>> * wait for the mono repo to happen, then we'll be able to make libFuzzer
>>> depend on clang. (Or no?)
>>> * move libFuzzer to a separate repo, parallel to compiler-rt? (not a large
>>> win, just listing as a choice)
>>> * anything else?
>>> 
>>> Does anyone see good reasons why libFuzzer should remain in llvm repo (as
>>> opposed to moving it to compiler-rt)?
>>> 
>> 
>> I'd like to move libFuzzer out of llvm/lib/, since it's definitely a
>> runtime library, and not compiler library infrastructure. compiler-rt seems
>> like the best place to put it for now, unless there are licensing concerns.
> 
> Maybe we should just move it under llvm/runtimes and set it up with a
> fairly simple cmake config? I think this makes it pretty trivial to
> build it with the just-built clang. It doesn't have terribly much to do
> with compiler-rt IMO - this isn't something that enables a compiler
> feature per se, it's more of its own thing.
> 
>> Mechanically, we can do this in one history-preserving commit by checking
>> out the entire SVN repo the way that the git-llvm script does. SVN users
>> and users of https://github.com/llvm-project/llvm-project will still see
>> the right history. The final monorepo will presumably also have accurate
>> history.
> 
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