Cryptic error when unable to write target file due to permission problems

[absurdhero]

On Mac OS, I was compiling a source file in a directory where I didn't have permission to create a new file like so:

$ rustc -o hello hello.rs
error: Could not write output: x86_64-a

It wasn't clear that this was an file IO issue and I could find no mention of this error in docs. The subject of the message was misleading and it looked to me like a code generation error due to the mention of "x86_64-a".

The error would be more clear if it printed the name of the file it was attempting to write instead of the architecture.

[huonw]

Triage: Appears to be slightly better, but I can only test on linux:

$ mkdir noperm && cd noperm/
$ echo 'fn main() {}' > test.rs
$ chmod -w .
$ rustc test.rs
error: Could not write output: Error opening output file 'test.o'

[huonw]

@pnkfelix says that the output is the same on OSX as on Linux, so I'm closing this. Feel free to reopen with more details about how to recreate the directory/file structure if you can still reproduce it.