[llvm-dev] FileCheck feature request- by default ignore IR-"headers"

[Justin Bogner via llvm-dev]

"Keane, Erich via llvm-dev" <llvm-dev at lists.llvm.org> writes:
> I hope this is the right place for this.
>
> Anyway, the primary usage for the utility "FileCheck" is to pattern
> match for specific values in a stream.  This is perfectly consistent
> and deterministic for the most part!  However, when validating clang's
> LLVM-IR generation, it is possible to make an invalid match against
> the top few generated lines (the LLVM-IR Headers), which are
> inconsistent.
>
> For example (from my personal pain), we have a test:
> clang/test/CodeGen/debug-info-macro.c that has a 'check-not' on the
> word "macros".  Unfortunately, my SVN workspace name was "ms_macros",
> which gave me a false match.  I'm a bit ashamed to say how long this
> took me to figure out :)

This is a bug in the test and an annoyingly common pitfall when it comes
to writing "CHECK-NOT" checks - it should be checking for something more
specific.

> Anywya, to my feature request: to prevent someone else from going
> through this pain again, would it be possible to have FileCheck ignore
> these first 4 lines as default behavior?  I suspect there might be a
> few tests that would want to validate those headers, though I expect
> those are the vast minority, so I would think this should be opt in.

Unfortunately this isn't really practical to do - FileCheck is
completely unaware of what kind of file it's checking, so it wouldn't
know when to skip those couple of lines (many tests are not IR!).