version of Rust you're using, etc.
Sometimes, a backtrace is helpful, and so including that is nice. To get
-a backtrace, set the `RUST_BACKTRACE` environment variable. The easiest way
+a backtrace, set the `RUST_BACKTRACE` environment variable to a value
+other than `0`. The easiest way
to do this is to invoke `rustc` like this:
```bash
- `make check-stage1-std NO_REBUILD=1` - test the standard library without
rebuilding the entire compiler
- `make check TESTNAME=<substring-of-test-name>` - Run a matching set of tests.
- - `TESTNAME` should be a substring of the tests to match against e.g. it could
- be the fully qualified test name, or just a part of it.
+ - `TESTNAME` should be a substring of the tests to match against e.g. it could
+ be the fully qualified test name, or just a part of it.
`TESTNAME=collections::hash::map::test_map::test_capacity_not_less_than_len`
or `TESTNAME=test_capacity_not_less_than_len`.
- `make check-stage1-rpass TESTNAME=<substring-of-test-name>` - Run a single