Compiling rustc on OSX 10.6 fails with "Symbol not found: __tlv_bootstrap"

[agrif]

The full relevant part of the error:

compile_and_link: x86_64-apple-darwin/stage0/lib/rustc/x86_64-apple-darwin/lib/libstd.dylib
dyld: Symbol not found: __tlv_bootstrap
  Referenced from: /Users/agrif/local/rust/x86_64-apple-darwin/stage0/bin/../lib/libstd-6425b930ca146ae9-0.9-pre.dylib
  Expected in: /usr/lib/libSystem.B.dylib
 in /Users/agrif/local/rust/x86_64-apple-darwin/stage0/bin/../lib/libstd-6425b930ca146ae9-0.9-pre.dylib

It looks like __tlv_bootstrap is a marker symbol for the thread local variables rust uses, and this is available in 10.7 but not 10.6.

@alexcrichton provided me with this snippet of LLVM code that fails to link in both GCC and Clang with the same error.

OSX 10.6 is still listed in the README as a supported platform. I'd love to be able to compile this under 10.6, but if not, remember to update that readme.

[emberian]

What even is __tlv_bootstrap? I can't find any references to it in the wild, except things not working.

[alexcrichton]

This is all related to LLVM's treatment of thread_local globals. Due to LLVM not being able to compile the small assembly snippet of mine, I'm pinning this on an LLVM limitation rather than a rust compiler error. Our options include:

• Drop support for 10.6
• Don't use #[thread_local] at all on OSX
• Add cfg(osx_version = "10.6") (where does it end?)

I'm not liking any of these options...

[huonw]

Another option: Add a feature detection mechanism, i.e. #[cfg(feature_supported="thread_local")]?

[agrif]

brson in the mozilla #rust IRC channel mentioned that the OSX builds are done on 10.7, so I assume that means it builds on 10.7, and that also explains why this failure on 10.6 went unnoticed.

[lkuper]

I have the same failure under 10.6.

[michaelbartnett]

Also running into this (MacOS 10.6.8, Xcode 4.2). Here's another terminal paste, much like the other: https://gist.github.com/michaelbartnett/8432437

[alexcrichton]

Closing as a result of #11952, we're dropping support for 10.6