This un-hardcodes the bootstrap tools passed into the Darwin stdenv and
thus allows us to quickly iterate on improving the design of the full
bootstrap process. We can easily change the contents of the bootstrap
tools and evaluate an entire bootstrap all the way up to real packages.
92188d9d17 broke the case where the user
has Xcode but not the command-line tools. So this commit restores
using xcrun to get the path to the SDK (falling back to / for the
non-Xcode case).
http://hydra.nixos.org/build/19953295
This makes stuff build with Xcode 6.1 on Mac OS X 10.9 (where we got
errors like "ld: file not found:
/usr/lib/system/libsystem_coreservices.dylib for architecture x86_64" due to the use of the 10.10 SDK).
In 3.3, a C++ class defined in a header will get a typeinfo symbol
like this (e.g. in Nix's src/libutil/util.o):
(__DATA,__datacoal_nt) weak external typeinfo for nix::BaseError
But in 3.4, this has changed to:
(__DATA,__datacoal_nt) weak external automatically hidden typeinfo for nix::BaseError
This causes the linker to change the symbol to:
(__DATA,__data) non-external (was signed char private external) typeinfo for nix::BaseError
i.e. losing its weak linkage. But without weak linkage, dynamic_cast
and other RTTI-based mechanisms (such as catching an exception of a
certain type) don't work across shared libraries / executables.
The clang compiler in the SDK doesn't have this behaviour, but it's
not clear exactly which version it is (it just says "based on LLVM
3.4svn").
Copying /usr/lib/system/libunwind.dylib at evaluation time doesn't
work (e.g. on Hydra). And copying binary system libraries is a bad
idea anyway for license reasons.
