[llvm-dev] lld: sigbus error handling

Rui Ueyama via llvm-dev
2017-10-24T01:30:44Z

On Mon, Oct 23, 2017 at 5:28 PM, Andrew Kelley <superjoe30 at gmail.com>
wrote:

> For Zig we use LLD as a library. So for us it would be better to avoid
> global state such as SIGBUS (or any other signal handlers), instead
> returning an error from the link function when linking fails. If lld can
> encapsulate this signal handling and prevent the application using lld from
> getting the signal directly, instead carefully handling the signal in LLD
> itself and translating it into a proper error code or message, this would
> be reasonable.
>

Signal handlers and signal masks are inherently process-wide, so there's no
way to encapsulate them to lld functions. So my plan is to change the name
of lld::{coff,elf}::link's `ExitEarly` parameter to `IsStandalone`, and we
(not only call exit(2) but also) set a signal handler only when the
argument is true. Since library users pass false to the parameter, it
shouldn't change the behavior of lld for the library use case.

On Mon, Oct 23, 2017 at 6:21 PM, Rui Ueyama via llvm-dev
<
> llvm-dev at lists.llvm.org> wrote:
>
>> 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?
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
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>>
>>
>
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