llvm dev - Mar 2016 - Need help with code generation

On 21 March 2016 at 17:20, James Molloy via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Rafael,
>
> How can a high quality product crash by design? I understand the lack of
> structured error handling, and I understand asserting (which in release
mode
> would be silent) on internal errors. But on an input? How can an
application
> be taken seriously when crashes are design features?
>
> And I certainly didn't see consensus or in fact the suggestion of this
in
> the other thread, unless I glazed over an important part.
>
It can crash because .o files are not user input. They are generated.
To get one you need a broken assembler or a broken hardware.

Sorry if lld is not the linker you want, but that is the one we are writing.

As for how it will be taken seriously, well, we seem to be on good
track to be able to link freebsd and to do so faster than gold.

Cheers,
Rafael

2016/03/21 22:23 "Rafael Espíndola" <rafael.espindola at
gmail.com>:
>
> On 21 March 2016 at 17:20, James Molloy via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Rafael,
> >
> > How can a high quality product crash by design? I understand the lack
of
> > structured error handling, and I understand asserting (which in
release
mode
> > would be silent) on internal errors. But on an input? How can an
application
> > be taken seriously when crashes are design features?
> >
> > And I certainly didn't see consensus or in fact the suggestion of
this
in
> > the other thread, unless I glazed over an important part.
> >
>
> It can crash because .o files are not user input. They are generated.
> To get one you need a broken assembler or a broken hardware.
>
> Sorry if lld is not the linker you want, but that is the one we are
writing.
>
> As for how it will be taken seriously, well, we seem to be on good
> track to be able to link freebsd and to do so faster than gold.
I think this point is worth emphasizing. LLD is actually much faster than
gold.
> Cheers,
> Rafael
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> I think this point is worth emphasizing. LLD is actually much faster than
> gold.
So's "exit(1)".

Tim.

I was writing a response but David and Tim got there first more eloquently.
+1 to both of them.

I also find your tone worryingly totalitarian, Rafael.
On Mon, 21 Mar 2016 at 21:23, Rafael Espíndola <rafael.espindola at
gmail.com>
wrote:
> On 21 March 2016 at 17:20, James Molloy via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Rafael,
> >
> > How can a high quality product crash by design? I understand the lack
of
> > structured error handling, and I understand asserting (which in
release
> mode
> > would be silent) on internal errors. But on an input? How can an
> application
> > be taken seriously when crashes are design features?
> >
> > And I certainly didn't see consensus or in fact the suggestion of
this in
> > the other thread, unless I glazed over an important part.
> >
>
> It can crash because .o files are not user input. They are generated.
> To get one you need a broken assembler or a broken hardware.
>
> Sorry if lld is not the linker you want, but that is the one we are
> writing.
>
> As for how it will be taken seriously, well, we seem to be on good
> track to be able to link freebsd and to do so faster than gold.
>
> Cheers,
> Rafael
>
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It seems that it is repeating the same discussion again, unfortunately. I
believe that everybody can at least accept either is reasonable choice.
Also, I'd like to mention that LLD developers who are actually hacking the
thing everyday are thinking that that is a reasonable choice as far as I
can tell. So why don't we go with the decision I wrote in the doc?

On Mon, Mar 21, 2016 at 10:35 PM, James Molloy <james at
jamesmolloy.co.uk>
wrote:
> I was writing a response but David and Tim got there first more
> eloquently. +1 to both of them.
>
> I also find your tone worryingly totalitarian, Rafael.
> On Mon, 21 Mar 2016 at 21:23, Rafael Espíndola <rafael.espindola at
gmail.com>
> wrote:
>
>> On 21 March 2016 at 17:20, James Molloy via llvm-dev
>> <llvm-dev at lists.llvm.org> wrote:
>> > Rafael,
>> >
>> > How can a high quality product crash by design? I understand the
lack of
>> > structured error handling, and I understand asserting (which in
release
>> mode
>> > would be silent) on internal errors. But on an input? How can an
>> application
>> > be taken seriously when crashes are design features?
>> >
>> > And I certainly didn't see consensus or in fact the suggestion
of this
>> in
>> > the other thread, unless I glazed over an important part.
>> >
>>
>> It can crash because .o files are not user input. They are generated.
>> To get one you need a broken assembler or a broken hardware.
>>
>> Sorry if lld is not the linker you want, but that is the one we are
>> writing.
>>
>> As for how it will be taken seriously, well, we seem to be on good
>> track to be able to link freebsd and to do so faster than gold.
>>
>> Cheers,
>> Rafael
>>
>
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----- Original Message -----
> From: "Rafael Espíndola via llvm-dev" <llvm-dev at
lists.llvm.org>
> To: "James Molloy" <james at jamesmolloy.co.uk>
> Cc: "llvm-dev" <llvm-dev at lists.llvm.org>, "Bruce
Hoult" <bruce at hoult.org>
> Sent: Monday, March 21, 2016 4:23:10 PM
> Subject: Re: [llvm-dev] Need help with code generation
> 
> On 21 March 2016 at 17:20, James Molloy via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> > Rafael,
> >
> > How can a high quality product crash by design? I understand the
> > lack of
> > structured error handling, and I understand asserting (which in
> > release mode
> > would be silent) on internal errors. But on an input? How can an
> > application
> > be taken seriously when crashes are design features?
> >
> > And I certainly didn't see consensus or in fact the suggestion of
> > this in
> > the other thread, unless I glazed over an important part.
> >
> 
> It can crash because .o files are not user input. They are generated.
> To get one you need a broken assembler or a broken hardware.
Linker inputs come from .a and .so files which are shipped and long-lived (i.e.
subject to file-system/transfer corruption), and might contain data crafted by a
malicious party. So, are we just talking about segfaults under
otherwise-controlled circumstances (i.e. I could install some signal handlers to
catch all such cases), or are we talking about arbitrary buffer overruns? The
latter seems like a potential security problem.

Thanks again,
Hal
> Sorry if lld is not the linker you want, but that is the one we are
> writing.
> 
> As for how it will be taken seriously, well, we seem to be on good
> track to be able to link freebsd and to do so faster than gold.
> 
> Cheers,
> Rafael
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> 
-- 
Hal Finkel
Assistant Computational Scientist
Leadership Computing Facility
Argonne National Laboratory