If you do `./configure --enable-debug --enable-optimization`, `make` will fail with: ``` rustc: x86_64-apple-darwin/stage1/lib/rustlib/x86_64-apple-darwin/lib/librustc Assertion failed: (T == dwarf::DW_TAG_typedef || T == dwarf::DW_TAG_const_type || T == dwarf::DW_TAG_volatile_type || T == dwarf::DW_TAG_restrict_type || T == dwarf::DW_TAG_enumeration_type), function isUnsignedDIType, file /Users/rgawdzik/dev/rust/src/llvm/lib/CodeGen/AsmPrinter/DwarfUnit.cpp, line 525. make: *** [x86_64-apple-darwin/stage1/lib/rustlib/x86_64-apple-darwin/lib/stamp.rustc] Abort trap: 6 ``` Fails on both mac, linux on master. This error does not occur if you only use `--enable-debug` or `--enable-optimization` exclusively.