Migrating dmd to D?

[Iain Buclaw]

On Feb 28, 2013 1:31 AM, "Walter Bright" <newshound2 at digitalmars.com> wrote:
>
> On 2/27/2013 4:57 PM, H. S. Teoh wrote:
>>
>> How will this work with the continual stream of fixes that the current
>> C++-based compiler is getting? I assume we're not just going to put DMD
>> development on hold.
>
>
> I've done many projects consisting of converting a medium sized code base
from one language to another. The way that works is to do it incrementally.
Incrementally means:
>
> 1. at each step (i.e. pull request) we will have a fully functioning D
compiler that passes its test suite
>
> 2. there is no divergence in code bases because there is not a divergent
code base.
>
>
>> Also, wouldn't this be a good time to review some of the current designs
>> in DMD that may be hampering the full implementation of features that
>> we'd like, such as discrepancies with TDPL, etc.? Would it make sense to
>> redesign some of the code currently causing hard-to-fix issues as we're
>> porting that part of DMD into D? It seems a bit counterproductive to
>> simply transcribe the current buggy code into D, only to rewrite it
>> later when (if) we finally get round to fixing it.
>
>
> My experience chiming in - never ever ever attempt to refactor while
translating. What always happens is you wind up with a mess that just
doesn't work.
>
>
>
>> Finally, I think somebody has brought up the idea of "freezing" a
>> particular subset of D that the D compiler can use in its own code,
>> preferably a reasonably simple subset that is safe from breaking changes
>> down the road (it would be pathetic if a breaking change causes the
>> compiler to be unable to compile itself, because the source code uses a
>> language construct that was later deemed to need redesign)g . As DMD is
>> ported over to D, it should be restricted to using only this subset of
>> the language, so that it does not hamper future developments of the
>> language unnecessarily.
>
>
> Experience chiming in - a successful model is that the HEAD is compiled
by the previous official release of D.
>

Once HEAD is compiled by the previous release (or system D compiler), it
might be a good practice for HEAD to compile itself too. Then this compiler
built by HEAD will then build the library.

Regards
Iain
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