Remove thread-blocking call to `libc::stat` in `Path::stat`

[alexcrichton]

This should instead use the rt::io::file interface which does not block the thread. Additionally, this should remove the default_stat functions in the path/mod.rs file along with related definitions.

This is a pretty good first project for anyone wanting to sink their teeth into some library work! It's a bit of refactoring and should result in a nice large negative diffstat!

[hatahet]

What about calls to lstat() in path/posix.rs?

[hatahet]

It seems that there is no 1-to-1 mapping of libc::stat to rt::io::FileStat. Particularly, the latter is missing fields, such as mode, and OS-specific attributes, such as birthtime on MacOS and FreeBSD. I suppose that FileStat will have to have those fields added to it.

[alexcrichton]

The lstat function should not exist in that current form, and it's fine to drop fields for now. A rust Path should work the same on all platforms, not create different structs with different fields (very easy to miscompile on other platforms).

[hatahet]

When I changed the implementation of Path::stat() in posix.rs to call rt::io::file::stat() and then make check, I hit a compiler error:

task '<unnamed>' failed at 'Unhandled condition: io_error: rt::io::IoError{kind: OtherIoError, desc: "no such file or directory", detail: None}', /Users/.../dev/local/github/rust/src/libstd/condition.rs:131
error: internal compiler error: unexpected failure
note: the compiler hit an unexpected failure path. this is a bug
note: try running with RUST_LOG=rustc=1 to get further details and report the results to github.com/mozilla/rust/issues
task '<unnamed>' failed at 'explicit failure', /Users/.../dev/local/github/rust/src/librustc/rustc.rs:395

I do have an export RUST_LOG=rustc=1, but nothing extra seems to be printed. Should I file a separate issue for this?

[alexcrichton]

The calls to rt::io::file::stat will raise on the io_error condition when they encounter an error. In this case it looks like the error was that a file was not found. The return value of stat will be None, but you'll need to explicitly catch the error as well for now (and ignore it or continue to propagate it).

[hatahet]

If it is fine to drop fields for now, I suppose we should remove tests that reference such fields. E.g. in libstd/run.rs:587 we have assert_eq!(parent_stat.st_dev, child_stat.st_dev); for two tests: test_keep_current_working_dir() and test_change_working_directory

[hatahet]

Both the fields in question exist in uv_stat_t, I suppose I will just add them to FileStat then in that case.

[alexcrichton]

Feel free to modify FileStat as much as you need, especially if there's information inside of uv_stat_t on all platforms, then feel free to add it in!