It is possible to get segfaults in many situations while using valac by giving to him relative paths.

Here's some examples of segfaults.

A simple patch is attached to fix those segfaults. But we should review all FileStream.open to avoid those crashes:

$ mkdir -p foo/bar
$ :> foo/bar/cow.vala
$ valac -C foo/bar/cow.vala -d foo
Segmentation fault

Another one:

$ mkdir -p foo/bar foo2
$ :> foo/bar/cow.vala
$ cd foo2
$ valac --library ../foo/bar/lib -C ../foo/bar/test.vala -d ../foo/bar

Do the --library should accept paths? I thought 'name' is just for 'library name' not library path.

Do we really want to concatenate all relative paths to the destination directory? shouldn't we just get the filename?

It is not specified anywhere which should be the correct way to react in such situations.