[llvm-dev] Need help with code generation

[Rafael Espíndola via llvm-dev]

On 21 March 2016 at 17:34, Tim Northover via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
>> My understanding is that clang and llvm themselves are designed this way
>> (crash when the unexpected happens).
>
> I don't think so. I'd view any Clang crash as a bug (probably to be
> prioritised below silent CodeGen and many others, but not "working as
> designed").
>
>> For example the fact that clang forks itself to be able to report diagnostics
>
> That seems like just trying to make our own job easier to me. I think
> the entire point of the fork is to get a backtrace we can fix, and
> point out where the user should send it.
>
>> llvm is full of report_fatal_error() (or worse, assertions that can fire on unexpected user input).
>
> A bit of a grey area since LLVM isn't itself a user-facing tool, but I
> think I'd still say that a report_fatal_error that's not actionable by
> the user is actually an LLVM bug. And a segfault definitely so.

It is completely trivial to crash llvm. A case I wrote today in
another thread while waiting for tests to run:

target triple = "x86_64-unknown-linux-gnu"
@".data" = global i32 42

That will crash "llc -filetype=obj". The fact that it is considered a
bug doesn't mean much if there is no coordinated effort to fix them.

Right now lld is already harder to crash than llvm. We are just being
honest about the fact that it is possible to craft a .o file that will
crash it.

Cheers,
Rafael