D, SCons, Dub

[Russel Winder via Digitalmars-d]

On Tue, 2017-04-18 at 07:34 +0000, Alex via Digitalmars-d wrote:
> 
[…]
> I know, I have been using your work in SCons to build in this 
> mode since it was first available.

Excellent. :-)

[…]
> > > 
> I realise there are no headers, that is the problem. SCons can't 
> tell whether a change to a module affects the interface, only 
> affects the implementation or only affects a unit test. This 
> means everything that imports a module is recompiled on every 
> edit, even if only the unit test was modified, or a formatting 
> change was made.

SCons should be immune to whitespace changes, but actual reformatting
is likely to be a change.

Hummm… it is not clear in my mind just now whether that dependency is
build into the SCons build DAG. Whilst the C and C++ builders go to
great lengths to deal with the #include dependency tree, I am not sure
the D tools parse the D source import dependency tree. It probably
should, but just now – I believe – it is just module by module
compilation. If there are API changes then SCons will not follow that
through for D codes. 
 
> I am not suggesting the D way is bad compared to C++, I am 
> suggesting we can have the best of both worlds by automatically 
> generating 'headers' or .di files from modules. Then having 
> dependent modules read only the .di file instead of the .d file.
> This way SCons won't recompile dependencies unless necessary. 
> This is the main purpose of using SCons (perfect incremental 
> builds) which is largely defeated currently by D.

I have never trodden the .di file path and so the SCons tools do not
generate them. A flag could easily be added so that an emitter of the
builder could generate the .di as well as the .o file. The tools are
not set up for that as yet, but it could be done.

Being sent small projects as test cases to drive adding features is
likely the best route. Feel free to send in issues on  https://github.c
om/russel/SCons_D_Experiment

[…]
> I know, I have been working through the guts of SCons for (a 
> little bit too long to mention)  trying to make it both output 
> two products with proper dependencies (.o and .di) and to find 
> the di files correctly. SCons seems to have an ability to find 
> the original .d files in the project even if the compiler can't.

It maybe that the missing link here is that the D builders currently do
not have emitters. With an emitter added doing the .di as well as .o
files should be very straightforward – but maybe not easy.

[…]
-- 
Russel.
=============================================================================
Dr Russel Winder      t: +44 20 7585 2200   voip: sip:russel.winder at ekiga.net
41 Buckmaster Road    m: +44 7770 465 077   xmpp: russel at winder.org.uk
London SW11 1EN, UK   w: www.russel.org.uk  skype: russel_winder
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: This is a digitally signed message part
URL: <http://lists.puremagic.com/pipermail/digitalmars-d/attachments/20170418/fb386fb1/attachment.sig>