Is support for MacOS 11 Big Sur real?

[kv9898]

My friend's M1 Macbook with Big Sur can run the rest of Positron normally, but not for ark.

However, my custom version of ark that explicitly sets target through the following lines in the GitHub Workflow does work for her:

            - name: Set macOS 11 deployment target
              run: |
                echo "MACOSX_DEPLOYMENT_TARGET=11" >> $GITHUB_ENV
                echo "RUSTFLAGS=-C link-args=-mmacosx-version-min=11" >> $GITHUB_ENV

I initially brought this query in #3732 (comment), but I don't think my issue belongs there. I think my issue is akin to #3812 but that was closed in favour of #3732. I also believe my PR posit-dev/ark#946 was closed too early. If 10.15 is no longer officially supported by Positron, I think shifting the minimum support to 11 is fair as that's the "official" minimum version for Mac.

[lionel-]

hmm indeed I now see the problem. The whole binary has been linked with the correct minos target:

> otool -l target/debug/ark | grep -A 5 LC_BUILD_VERSION
      cmd LC_BUILD_VERSION
  cmdsize 32
 platform 1
    minos 11.0
      sdk 11.0
   ntools 1

But I see that ZeroMQ, our main (or only?) dependency that uses C++, has several object files compiled with a very recent minos target:

otool -l target/debug/deps/libzmq_sys-d7e0ad8e3c20ece0.rlib | grep -A 5 LC_BUILD_VERSION
      cmd LC_BUILD_VERSION
  cmdsize 24
 platform 1
    minos 11.0  # ok
      sdk n/a
   ntools 0
--
      cmd LC_BUILD_VERSION
  cmdsize 24
 platform 1
    minos 11.0  # ok
      sdk n/a
   ntools 0
--
      cmd LC_BUILD_VERSION
  cmdsize 24
 platform 1
    minos 26.0  # oops
      sdk 26.0
   ntools 0
--
      cmd LC_BUILD_VERSION
  cmdsize 24
 platform 1
    minos 26.0
      sdk 26.0
   ntools 0
--
      cmd LC_BUILD_VERSION
  cmdsize 24
 platform 1
    minos 26.0
      sdk 26.0
   ntools 0
--
# This goes on

If I build with:

MACOSX_DEPLOYMENT_TARGET=11 cargo build

I get the expected:

cmd LC_BUILD_VERSION
cmdsize 24
platform 1
minos 11.0
sdk n/a
ntools 0
--
cmd LC_BUILD_VERSION
cmdsize 24
platform 1
minos 11.0
sdk n/a
ntools 0
--
cmd LC_BUILD_VERSION
cmdsize 24
platform 1
minos 11.0
sdk 26.0
ntools 0

...

As I understand it's fine to have sdk: 26.0 (meaning it's been built with latest SDK on my machine) as long as the target minos is correctly set.

[lionel-]

Moved to an issue at #10192