[llvm-dev] Need help with code generation

[Rui Ueyama via llvm-dev]

On Tue, Mar 22, 2016 at 12:41 AM, David Blaikie via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

>
>
> On Mon, Mar 21, 2016 at 4:35 PM, Rafael Espíndola <
> rafael.espindola at gmail.com> wrote:
>
>>
>> On Mar 21, 2016 5:49 PM, "David Blaikie" <dblaikie at gmail.com> wrote:
>> >
>> >
>> >
>> > On Mon, Mar 21, 2016 at 2:46 PM, Rafael Espíndola <
>> llvm-dev at lists.llvm.org> wrote:
>> >>
>> >> 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.
>> >
>> >
>> > I think it does, actually - that patches will be accepted to fix pretty
>> much any crash in LLVM. (llc isn't a user facing tool, so that's a
>> praticularly low priority -
>>
>> I am pretty sure clang crashes if you translate the above example to C.
>>
>> Philosophical question: what is the difference of a non bug and a bug of
>> such low priority that it is never fixed?
>>
>  One where contributors are encouraged to provide patches to fix things,
> versus one where contributors are told that there is a high bar to get such
> a patch contributed seems like a pretty big difference to me.
>
> It changes who's willing to contribute to the project, or build tools
> based on it.
>

The documented policy should handle that issue.


> - David
>
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