ld64 is threaded, and uses a worker for each CPU to parse input files. But
there's a bug in the parser causing dependencies to be calculated differently
based on which files have already been parsed.
As a result, builders with more CPUs are more likely to see non-determinism.
This looks to have been fixed in a newer version of ld64, so just disable
threading for now. There's no noticible slowdown.
In some cases (Travis), sources and build caches may be moved around in-between
builds, and we can't necessarily trust that everything is still intact.
This introduces pre-build checks that verify against stashed checksums.
Note that this will cause all sources to be re-downloaded, since cached sources
weren't trustworthy before this.
tl;dr: Update to the newer stable toolchain and SDK for OSX without giving up
any backwards compatibility. We can move to clang 3.5 as a next step which
allows use to use libc++ and the 10.10 sdk, but we'll need to find a build that
works in gitian/travis first.
Switch to a new, better maintained fork of cctools:
https://github.com/tpoechtrager/cctools-port
I've forked this and will be working on it some as well:
https://github.com/theuni/cctools-port
This brings in:
cctools v862
ld64: v241.9
It also fixes 64bit builds, so there's no longer any need to use a 32bit clang.
Since clang is no longer tied to an old/crusty 32bit build, clang has been
upgraded to 3.3. Unfortunately, there's a bug in 3.4 that breaks builds. 3.5
works fine, but there are no binary builds compatible with precise, which is
currently used for gitian and travis. We could always build our own if
necessary.
After updating to stable clang/linker/cctools, it's possible to use a more
recent SDK. The current SDK (10.7) through the most recent 10.10 have all been
built/tested successfully, both with and without 10.6 compatibility. However,
10.10 requires clang 3.5.
SDKs >= 10.9 use libc++ rather than libstdc++. This is verified working as well.
Cory Fields