[llvm-dev] Proposal: introduce dependency on abseil when building benchmarks

[Mircea Trofin via llvm-dev]

On Tue, Oct 5, 2021 at 8:57 PM Reid Kleckner <rnk at google.com> wrote:

> On Thu, Sep 30, 2021 at 10:08 AM Mircea Trofin via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> TL;DR; When either of LLVM_BUILD_BENCHMARKS or LIBCXX_INCLUDE_BENCHMARKS
>> are enabled, as well as for llvm-test-suite, a dependency to abseil would
>> either be auto-downloaded by the build system, or need to be
>> user-specifiable, or provided in the source tree.
>>
>
> Could you please elaborate on which of these approaches will be used for
> LLVM? How will this affect regular LLVM developers?
>
Assuming regular LLVM developers means developers that don't enable
LLVM_BUILD_BENCHMARKS, nor LIBCXX_INCLUDE_BENCHMARKS, then they are not
affected.

The current PR in "benchmarks" upstream is set up so that it will either
download the abseil dependency at build time, or, if the location of abseil
is specified via a cmake flag, then it uses that one (which covers the last
2 options). I don't know if the first option is acceptable by those that
enable LLVM_BUILD_BENCHMARKS / LIBCXX_INCLUDE_BENCHMARKS, and this is
something I'm hoping to discover with this thread. If it is acceptable,
it's a transparent option, so it won't directly impact those users either.

>
> ----
>
> This is truly unrelated, but I have a lot of feelings about this, and I
> will use this opportunity to inappropriately complain that the benchmarks
> library has been spamming me with cmake warnings about std::regex for
> years: https://bugs.llvm.org/show_bug.cgi?id=38874 The CMake step really
> ought to be warning-clean.
>
Ack. Added an issue on the project side:
https://github.com/google/benchmark/issues/1236 (maybe it has better
visibility)
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