llvm dev - Jan 2013 - [LLVMdev] Using C++'11 language features in LLVM itself

On 1/10/2013 12:11 PM, dag at cray.com wrote:
> Pawel Wodnicki <root at 32bitmicro.com> writes:
> 
>>  Clang is good enough to bootstrap itself on practically
>> any platform I can think of or it can be cross-bootstrapped
>> if needed.
> 
> You're completely ignoring communities that compile code outside
> llvm+clang.  Any compiler chosen by that group has to be able to
> correctly compile hundres if not thousands of source code files.  It is
> not easy to find such a compiler and that makes it an arduous process to
> upgrade.  Of course upgrades are done, but they're done conservatively.
> 
>                             -David
> 
> 
 As you have pointed out the reality is that for a long time
there will be a lot of different C++ code to maintain and for
practical reasons it makes no sens to throw away time tested tools
just to use some modern C++ style.  At the same time I am not
convinced that it is worth the effort to introduce some C++11
features into LLVM and try to stay compatible with all these other
compilers.

 So if the goal is to be able to use *any* however broken C++ compiler
to build LLVM and stay compatible with the platform compiler
then perhaps we should approach it differently. Ideally source
translation in clang could be used to "lower" C++11 code to
either C++03 or even C++98, worst case just use CPP backend.

 I realize that Cfront approach does not have a good
track record but this could be a C++front translating
C++11 to older version of the C++ language.

Paweł

Pawel Wodnicki <root at 32bitmicro.com> writes:
>  So if the goal is to be able to use *any* however broken C++ compiler
> to build LLVM and stay compatible with the platform compiler
No one ever said that.  We're simply trying to determine which
reasonable set of compilers to support.

                                -David

On Thu, Jan 10, 2013 at 2:11 PM, Pawel Wodnicki <root at 32bitmicro.com>
wrote:
> On 1/10/2013 12:11 PM, dag at cray.com wrote:
> > Pawel Wodnicki <root at 32bitmicro.com> writes:
> >
> >>  Clang is good enough to bootstrap itself on practically
> >> any platform I can think of or it can be cross-bootstrapped
> >> if needed.
> >
> > You're completely ignoring communities that compile code outside
> > llvm+clang.  Any compiler chosen by that group has to be able to
> > correctly compile hundres if not thousands of source code files.  It
is
> > not easy to find such a compiler and that makes it an arduous process
to
> > upgrade.  Of course upgrades are done, but they're done
conservatively.
> >
> >                             -David
> >
> >
>
>  As you have pointed out the reality is that for a long time
> there will be a lot of different C++ code to maintain and for
> practical reasons it makes no sens to throw away time tested tools
> just to use some modern C++ style.  At the same time I am not
> convinced that it is worth the effort to introduce some C++11
> features into LLVM and try to stay compatible with all these other
> compilers.
>
It's not a matter of *all* compilers.  Once we establish a baseline, it
only matters for those compilers.

>
>  So if the goal is to be able to use *any* however broken C++ compiler
> to build LLVM and stay compatible with the platform compiler
> then perhaps we should approach it differently. Ideally source
> translation in clang could be used to "lower" C++11 code to
> either C++03 or even C++98, worst case just use CPP backend.
>
>  I realize that Cfront approach does not have a good
> track record but this could be a C++front translating
> C++11 to older version of the C++ language.
>
I wouldn't expect this to be a part of LLVM itself; if someone needs to
support an old/broken compiler, they can make this work themselves.

>
> Paweł
>
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>


-- 

Thanks,

Justin Holewinski
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On 1/10/2013 1:28 PM, Justin Holewinski wrote:
>
> It's not a matter of *all* compilers.  Once we establish a baseline, it
> only matters for those compilers.
So far it appears that the baseline is very limited, compared to the set 
of compilers actively in use.

-Krzysztof

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