Previously, Miri would always print a backtrace including all frames
when encountering an error. This adds -Zmiri-backtrace which defaults
to 1, internally called BacktraceStyle::Short. By default, backtraces
are pruned to start at __rust_begin_short_backtrace, similar to std.
Then we also remove non-local frames from the bottom of the trace.
This cleans up the last one or two shims outside main or a test.
Users can opt out of pruning by setting -Zmiri-backtrace=full, and will
be automatically opted out if there are no local frames because that
means the reported error is likely in the Rust runtime, which this
pruning is crafted to remove.
In user interface, added a new flag `-Zmiri-isolation-error` which
takes one of the four values -- hide, warn, warn-nobacktrace, and
abort. This option can be used to configure Miri to either abort or
return an error code upon executing isolated op. If not aborted, Miri
prints a warning, whose verbosity can be configured using this flag.
In implementation, added a new enum `IsolatedOp` to capture all the
settings related to ops requiring communication with the
host. Old `communicate` flag in both miri configs and machine
stats is replaced with a new helper function `communicate()` which
checks `isolated_op` internally.
Added a new helper function `reject_in_isolation` which can be called
by shims to reject ops according to the reject_with settings. Use miri
specific diagnostics function `report_msg` to print backtrace in the
warning. Update it to take an enum value instead of a bool, indicating
the level of diagnostics.
Updated shims related to current dir to use the new APIs. Added a new
test for current dir ops in isolation without halting machine.
move OsStr helpers to a separate file
Moved OsStr read/write functions from `src/helpers.rs` to `src/shims/os_str.rs`, in order to keep `src/helpers.rs` from bloating too much.
Add directory-related shims
This PR adds support for `mkdir`, `rmdir`, `opendir`, `closedir`, and `readdir64_r`.
Open directory streams are tracked through a HashMap indexed by pointer locations, which holds directory iterators. Since `DIR` is an opaque type in glibc, I represent them with 1-byte allocations, and then just use their pointers in HashMap lookups.
Tests are included to exercise the new functionality.
