Upgrade abseil to 20230802.1

[mudge]

RE2 2023-09-01 was released a week ago and there is a more recent LTS version of Abseil for us to use. However, when I initially pushed this to our v2.0.x branch, it looks like there are quite a few build failures to investigate.

[mudge]

If it’s a distraction right now, we could skip the abseil upgrade but it’d be good to know why it doesn’t work when the January release does.

[stanhu]

It looks like there are two main issues:

1. macOS (https://github.com/mudge/re2/actions/runs/6130653443/job/16639942206): absel::optional is aliased to C++17 std::optional, but the call to value() (introduced in abseil-cpp via https://github.com/abseil/abseil-cpp/commit/751ade00ee347abef5dac7248db851e3f2012e14) is only available starting in macOS 10.14. Even though the macOS SDK 11.1 is used, I'd have to presume the compiler tries to target a lower minimum target version:

 [ 97%] Building CXX object absl/status/CMakeFiles/status.dir/status.cc.o
/tmp/d20230909-93-us36r9/tmp/arm64-apple-darwin/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/status/status.cc:126:51: error: 'value' is unavailable: introduced in macOS 10.14
  if (index.has_value()) return (*payloads)[index.value()].payload;
                                                  ^

I think we might be able to set ABSL_OPTION_USE_STD_OPTIONAL to 0 to disable this aliasing, or consider raising the macOS minimum version. clang --help shows this option:

-mmacosx-version-min=<value>
                      Set Mac OS X deployment target

2. Windows (https://github.com/mudge/re2/actions/runs/6130653443/job/16639942231):

[ 37%] Building CXX object absl/synchronization/CMakeFiles/synchronization.dir/internal/create_thread_identity.cc.obj
In file included from /tmp/d20230909-93-l6kcab/tmp/x86_64-w64-mingw32/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/synchronization/internal/create_thread_identity.cc:21:
/tmp/d20230909-93-l6kcab/tmp/x86_64-w64-mingw32/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/synchronization/internal/waiter.h:44:2: error: #error ABSL_WAITER_MODE is undefined
   44 | #error ABSL_WAITER_MODE is undefined
      |  ^~~~~
/tmp/d20230909-93-l6kcab/tmp/x86_64-w64-mingw32/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/synchronization/internal/waiter.h:51:5: warning: "ABSL_WAITER_MODE" is not defined, evaluates to 0 [-Wundef]
   51 | #if ABSL_WAITER_MODE == ABSL_WAITER_MODE_FUTEX
      |     ^~~~~~~~~~~~~~~~
In file included from /tmp/d20230909-93-l6kcab/tmp/x86_64-w64-mingw32/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/synchronization/internal/create_thread_identity.cc:21:
/tmp/d20230909-93-l6kcab/tmp/x86_64-w64-mingw32/ports/abseil/20230802.0/abseil-cpp-20230802.0/absl/synchronization/internal/waiter.h:52:16: error: 'FutexWaiter' does not name a type
   52 | using Waiter = FutexWaiter;
      |                ^~~~~~~~~~~
make[2]: *** [absl/synchronization/CMakeFiles/synchronization.dir/build.make:92: absl/synchronization/CMakeFiles/synchronization.dir/internal/create_thread_identity.cc.obj] Error 1
make[1]: *** [CMakeFiles/Makefile2:4540: absl/synchronization/CMakeFiles/synchronization.dir/all] Error 2

There appears to be a workaround: https://github.com/abseil/abseil-cpp/issues/1510#issuecomment-1694249704.

[stanhu]

@mudge I think this is ready to go.

[mudge]

Updated for the recently released 20230802.1 (~note I removed https://github.com/mudge/re2/pull/95/commits/c284a7e2bc9c873ce756b4b39e17568d40f8b6ea just to see if that regression has been fixed but we may need to restore it~ restored as it looks like it is still a problem).

[mudge]

@stanhu any chance you could take a look at this? The Windows failures seem different to with patch level 0.

undefined reference to `absl::lts_20230802::synchronization_internal::Win32Waiter::Win32Waiter()

[mudge]

Out of interest, is MacPorts providing a version of Abseil that works with versions of macOS older than 10.14? See https://github.com/judaew/macports-ports/blob/master/devel/abseil/Portfile

[stanhu]

std::optional was added in C++17, and I see that they have set C++14 in https://github.com/judaew/macports-ports/blob/c536e357838df685f32fdedc7b74dd5d4f0325ce/devel/abseil/Portfile#L68. This might avoid the need to upgrade macOS. Maybe for macOS we can use C++14.

[mudge]

std::optional was added in C++17, and I see that they have set C++14 in https://github.com/judaew/macports-ports/blob/c536e357838df685f32fdedc7b74dd5d4f0325ce/devel/abseil/Portfile#L68. This might avoid the need to upgrade macOS. Maybe for macOS we can use C++14.

Good spot. Given Abseil only needs C++14 (and RE2 follows suit), I’ve set our MiniPortile recipes to only target that standard and it seems to fix the macOS build without dropping support for older versions.

[stanhu]

Did this branch drop 0b57520e4f8b689bb6212f7d20f73d154a26c057?

[mudge]

Yes, I've restored it now (I was trying to see what was and wasn't required with patch level 1).

[mudge]

The build is now green and (aside from the necessary workaround for https://github.com/abseil/abseil-cpp/issues/1510) I'm happier with the diff especially as we're not dropping support for any existing users.

[mudge]

If you're happy, I'd be tempted to merge this but not include it in a release until RE2 2023-10-01 is out (assuming it has a monthly release cadence now).

[mudge]

I've raised https://github.com/mudge/re2/pull/111 to partially automate this sort of thing in future: it's set to run on the first of the month and raise a PR with an updated dependencies.yml (if there are any releases). I'm tempted to merge that, trigger it manually and then cherry pick these commits onto the PR that is automatically raised.

[stanhu]

If you're happy, I'd be tempted to merge this but not include it in a release until RE2 2023-10-01 is out (assuming it has a monthly release cadence now).

Sounds good!

https://github.com/mudge/re2/pull/112 didn't run CI. Does the user need to be approved?

[mudge]

I think it’s due to https://github.com/peter-evans/create-pull-request/blob/main/docs/concepts-guidelines.md#triggering-further-workflow-runs I’ll try one of the workarounds and try triggering it again to make sure it runs CI too.

[mudge]

Closing in favour of https://github.com/mudge/re2/pull/113 as that PR was raised automatically.