[swift-dev] [Suggestion] swift/utils/update-checkout should keep llvm/clang up-to-date

Kevin Ballard kevin at sb.org
Mon Feb 8 22:55:42 CST 2016

The script already updates 9 repositories by default, including the
various corelibs repos. I'd say it's worth updating llvm and clang too,
since having an out-of-date llvm or clang can prevent swift from
building. I'm not sure about llbuild, since I don't really know much
about it or how often it updates, but I'm tempted to just get rid of the
--all flag entirely. I'll submit a PR.

-Kevin Ballard

On Mon, Feb 8, 2016, at 05:07 PM, Jordan Rose wrote:
>> On Feb 8, 2016, at 16:34, Michael Gottesman via swift-dev <swift-
>> dev at swift.org> wrote:
>>> On Feb 8, 2016, at 3:54 PM, Kevin Ballard <kevin at sb.org> wrote:
>>> On Mon, Feb 8, 2016, at 03:33 PM, Michael Gottesman wrote:
>>>>> On Feb 8, 2016, at 3:09 PM, Kevin Ballard via swift-dev <swift-
>>>>> dev at swift.org> wrote:
>>>>> I was surprised to discover that swift/utils/update-checkout
>>>>> doesn't update LLVM/clang by default. Looking at the script, it
>>>>> supports a --all flag to update those (and llbuild too), but that
>>>>> led to the second surprise, which is that the script doesn't make
>>>>> any attempt to ensure it's checking out a compatible version of
>>>>> llvm/clang, it just runs `git fetch` and `git rebase FETCH_HEAD`.
>>>> We ensure that the trunk stable clang/llvm branches are always in
>>>> sync. So just rebasing head should be sufficient.
>>> Ah right, the llvm/clang checkouts are to copies of llvm/clang
>>> instead of to the original.
>>> In that case, why doesn't the update-checkout script update
>>> llvm/clang by default? The only reason I can think of to not update
>>> it (besides for when you're intentionally targeting a non-stable
>>> version of llvm/clang because you're working on migrating it) is to
>>> avoid having to recompile llvm/clang if a backwards-compatible
>>> change happens to llvm/clang, but I assume the llvm/clang repos
>>> aren't updated very often, and when they are updated we all should
>>> probably update our checkouts of it even if we don't get compilation
>>> errors.
>> That is most likely an oversight. Pull request and assign to me?
> IIRC Dmitri was concerned about doing more serialized network requests
> on slow connections.
> Jordan
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