[cfe-dev] Separating clang-tools-extra from clang in LLVM_ENABLE_PROJECTS

[Nico Weber via cfe-dev]

Yeah, it probably makes sense to move some of those over to
clang-tools-extra as well.

In my mind, clang is the core compiler stuff (that for historical reasons
has a bunch of tooling stuff that happened to happen before clang-tidy was
a thing), and clang-tools-extra is stuff built on top of clang's libs.

On Thu, Feb 14, 2019 at 3:49 PM James Y Knight <jyknight at google.com> wrote:

> I really don't understand what the intended purpose of clang-tools-extra
> is. Why do I want to build clang-format, clang-fuzzer, clang-refactor, and
> a bunch of other stuff by default, but not clang-query, clang-tidy, etc? I
> cannot understand the distinction there.
>
> On Wed, Feb 13, 2019 at 6:15 PM Reid Kleckner via cfe-dev <
> cfe-dev at lists.llvm.org> wrote:
>
>> The context is https://reviews.llvm.org/D58157
>>
>> Back when Mehdi originally introduced the LLVM_ENABLE_PROJECTS cmake
>> variable, people were discussing the idea of folding clang-tools-extra into
>> clang, if we moved to multiple git repos away from a monorepo. To support
>> that goal, this code was added:
>> https://github.com/llvm/llvm-project/blob/master/llvm/CMakeLists.txt#L144
>>       # There is a widely spread opinion that clang-tools-extra should be
>> merged
>>       # into clang. The following simulates it by always enabling
>> clang-tools-extra
>>       # when enabling clang.
>>       if (proj STREQUAL "clang")
>>         set(LLVM_EXTERNAL_CLANG_TOOLS_EXTRA_SOURCE_DIR
>> "${CMAKE_CURRENT_SOURCE_DIR}/../clang-tools-extra")
>>       endif()
>>
>> This makes it so that if you're building clang, you're building
>> clang-tidy, clangd, etc. However, we have use cases where we want to check
>> out the monorepo and just build clang, so we wanted to remove that block.
>>
>> The upshot is that if you use LLVM_ENABLE_PROJECTS today and you want to
>> build clang tools, you will have to add "clang-tools-extra" to your CMake
>> invocation after D58157 lands. We've identified the one upstream buildbot
>> that uses this variable and plan to update it, but if you have downstream
>> bots using this variable, you may also need to add "clang-tools-extra" to
>> build clang-tidy & co.
>>
>> We have some consensus that this is the direction we want to go in the
>> code review from Sam Mccall, Shoaib, myself, and Nico, but please let us
>> know if you think this is the wrong direction.
>> _______________________________________________
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>>
>
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