libgreen/rustuv cant write huge files

[tfogal]

It seems libgreen cannot write large files. See the gist at:

https://gist.github.com/tfogal/9762303#file-simple-rs

See specifically the 'dumpf32' implementation.

When running with rust from 2014-03-21 (2014032104056eae7dfsaucy) on Ubuntu, the output file in this example is only 2147479552 bytes, whereas it should be exactly 4000000000 bytes.

This was fixed on 2014-03-25 in 2014032104056eae7dfsaucy. However, one can induce failure by forcing libgreen, via:

extern crate green;
extern crate rustuv;
...
#[start]
fn start(argc: int, argv: **u8) -> int { green::start(argc, argv, main) }

The 'rustuv' is critical to prevent an early crash calling "Result::unwrap() on an Err value, but it limits the output file size as above.

From talking with @huonw and @eddyb on IRC, this appears to be an issue with libuv. eddyb pinpointed it to:

https://github.com/mozilla/rust/blob/master/src/librustuv/uvll.rs#L371-L384

the issue appears to be a mismatch in the type given and taken to/by libuv.

@eddyb pinged the libuv folks, who said this aspect has recently changed and Rust should upgrade before working around the current code. uv_fs_write apparently takes an array of buffers now, in particular.

[tfogal]

This is likely joyent/libuv#1215.