Rust build fails on Solaris after: Implement file_lock feature

[psumbera]

Solaris OS doesn't support flock() and thus Rust fails to build after #130999 :

d2cdc76256313e8f23f585107c43badb49d5473d is the first bad commit
commit d2cdc76256313e8f23f585107c43badb49d5473d
Author: Christopher Berner [<me@cberner.com>](mailto:me@cberner.com)
Date:   Sun Sep 22 16:58:44 2024 -0700

    Implement file_lock feature
    
    This adds lock(), lock_shared(), try_lock(), try_lock_shared(), and
    unlock() to File gated behind the file_lock feature flag

with following error:

error: linking with `gcc` failed: exit status: 1
  |
  = note: LC_ALL="C" PATH="/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-sysroot/lib/rustlib/x86_64-pc-solaris/bin:/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0/lib/rustlib/x86_64-pc-solaris/bin:/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0/lib/rustlib/x86_64-pc-solaris/bin:/usr/gnu/bin/:/usr/gcc/13/bin:/usr/bin" VSLANG="1033" "gcc" "-m64" "/tmp/rustczm3gUt/symbols.o" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/deps/rustc_main-f7e62c1025f5dce2.rustc_main.39965e3472e7b77a-cgu.0.rcgu.o" "-Wl,-z,ignore" "-Wl,-Bdynamic" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/deps/librustc_driver-60ae461c5c39901a.so" "-Wl,-Bstatic" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-sysroot/lib/rustlib/x86_64-pc-solaris/lib/libcompiler_builtins-579d025a05650947.rlib" "-Wl,-Bdynamic" "-lrt" "-ldl" "-lm" "-lkstat" "-lsocket" "-lz" "-lstdc++" "-lsendfile" "-llgrp" "-lsocket" "-lposix4" "-lpthread" "-lresolv" "-lgcc_s" "-lc" "-lm" "-lrt" "-lpthread" "-lsendfile" "-llgrp" "-L" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/build/psm-daa576ffce68f706/out" "-L" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/build/blake3-2e711e7084babad6/out" "-L" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/build/blake3-2e711e7084babad6/out" "-L" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/build/rustc_llvm-2c65a157dbd38377/out" "-L" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/llvm/lib" "-o" "/builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/deps/rustc_main-f7e62c1025f5dce2" "-nodefaultlibs" "-Wl,-z,origin" "-Wl,-rpath,$ORIGIN/../lib"
  = note: Undefined            first referenced
           symbol                  in file
          flock                               /builds/psumbera/rust-lang-build/build/x86_64-pc-solaris/stage0-rustc/x86_64-pc-solaris/release/deps/librustc_driver-60ae461c5c39901a.so
          ld: fatal: symbol referencing errors
          collect2: error: ld returned 1 exit status

[cberner]

Oh, sorry about that breakage. Is there a way for me to test all the Tier 2 targets to make sure they compile? I can send a PR to fix this, but don't have a Solaris machine for testing

[psumbera]

For Solaris fcntl locking can be considered. But this will not work within one process. The semantic is different against flock().

You should be able to play with Solaris via https://portal.cfarm.net/machines/list/ (cfarm215 and cfarm216). But previous registration is needed.

[cberner]

Thanks, I requested an account there.

[cberner]

Still waiting for access, so I haven't been able to test this fix. It seems pretty trivial though, so hopefully it's correct

[ivmarkov]

@cberner The new flock API also broke ESP-IDF (another Tier 2 target a Tier 3 target - a single-process embedded one).

As per here, the flock API specifically would never be supported on the ESP-IDF as it is a single-process OS and flock is all about multi-process locking.

The fix in #132977 should take care of the issue for ESP IDF as well I think, simply because it only enables the flock APIs for a few explicitly enumerated platforms, and ESP-IDF is not one of these.

[cberner]

Yep, I didn't realize how many OSs use the unix implementation directory in the standard library, in my original PR. I think #132977 will fix all of them, like you said