Steps to reproduce:
1. compile any vala code (you probably have to use debug config)
2. debug vala application

What happens:
Executable contains absolute(!) paths where source files resided before compilation.

In Fedora 24's tracker build I get lines like these in backtraces:

+ Trace 236545

What should happen:
As C applications behave, vala paths should be relative to project root.

Additional info:
• Reproducible builds are only possible when having the exact same filesystem layout. Reproducible builds would be good for checking integrity of both your distribution and your compiler
• Data leak

Created attachment 350591 [details] [review]
codegen: Don't include the full absolute path in line directives

Only write the source's filename without any path.

Review of attachment 350591 [details] [review]:

If possible, I think the patch should make use of context.basedir
If context.basedir is "." then remove the current working directory file path from the source reference, otherwise remove context.basedir path?

Created attachment 350848 [details] [review]
codegen: Don't include the full absolute path in line directives

Only write source's filename prepended by the path relative to the
directory the valac call origined from.

Attachment 350848 [details] pushed as 49e5fc6 - codegen: Don't include the full absolute path in line directives