[llvm-dev] lld: sigbus error handling

[Rui Ueyama via llvm-dev]

But that would disable mmap IO on systems that don't support fallocate. I'm
not sure if OpenBSD people are for example happy about that.

On Mon, Oct 30, 2017 at 2:03 PM, Rafael Avila de Espindola <
rafael.espindola at gmail.com> wrote:

> Rui Ueyama via llvm-dev <llvm-dev at lists.llvm.org> writes:
>
> > If your system does not support fallocate(2), we use ftruncate(2) to
> create
> > an output file. fallocate(2) succeeds even if your disk have less space
> > than the requested size, because it creates a sparse file. If you mmap
> such
> > sparse file, you'll receive a SIGBUS when the disk actually becomes full.
> >
> > So, lld can die suddenly with SIGBUS when your disk becomes full, and
> > currently we are not doing anything about it. It's sometimes hard to
> notice
> > that that was caused by the lack of disk space.
> >
> > I wonder if we should print out a hint (e.g. "Bus error -- disk full?")
> > when we receive a SIGBUS. Any opinions?
>
> I think we should change the llvm implementation of resize_file to fail
> if it cannot allocate the space. That is, it should only use ftruncate
> on OS X where apparently HFS allocates space with it.
>
> If resize_file fails than lld can fail gracefully or use annonymous
> memory and a plain write instead of mmap for producing the output.
>
> Cheers,
> Rafael
>
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