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From Andre Fischer <>
Subject Re: [proposal] replace with a central Makefile.
Date Fri, 18 Oct 2013 14:52:32 GMT
On 18.10.2013 15:58, janI wrote:
> On 18 October 2013 15:00, Andre Fischer <> wrote:
>> On 18.10.2013 14:02, janI wrote:
>>> sd
>>> On 18 October 2013 13:36, Andre Fischer <> wrote:
>>>   On 18.10.2013 11:32, janI wrote:
>>>>   Hi.
>>>>> due to the discussion in thread "Mentor a new build system", I have
>>>>> made a
>>>>> proposal for a central Makefile located in main.
>>>>>   Hi Jan,
>>>> it is great that you are going to improve this part of the build system.
>>>>    But I think that we need more details about how the proposed build
>>>> system
>>>> works.  Without them I can not really evaluate the proposal.
>>>>   First of all, I agree with juergens remarks that this should be
>>> discussed
>>> before implemented, hence the wiki page.
>>> Secondly this has nothing directly to do with the proposed build system,
>>> its a simple replacement of in the current system.
>> Yes, that is how I understood it.  I just did not know how to call the
>> replacement.
>>> I know that works, but having a Makefile in main, would make us
>>> one step closer on being compatible with the distros. To me this job is a
>>> simple cleanup, not something we deadly need, but nice to have.
>>>   Some remarks regarding the missing options:
>>>> --from <module>
>>>>      This is one of the more important options and one that I use
>>>> frequently
>>>> (also in the form --all:<module>).
>>>>      Note that if you are in <moduleA> and call 'make --from <moduleB>'
>>>> then
>>>> all modules are built
>>>>      a) which <moduleA> depends on
>>>>      b) but not those that <moduleB> depends on
>>>>      c) Both <moduleA> and <moduleB> are built.
>>>>   I have changed the documentation.
>>> I use the --all:<module> myself very often, and have changed the
>>> documentation, because it is of course supported.
>>> The difference is that you do the call in main, but that is a minor detail
>>> that can be easily corrected (have <module>/Makefile calling
>>> main/Makefile.
>>> I have also changed documentation on --html due to juergens comments.
>> I am not sure that we understand --from and --since in the same way so I
>> will try to explain what I think they do.
>> Let's imagine that we have a simple project with modules A, B, C, D and E.
>> where B depends on A, C on B, D on C, and E on D.
>> A ' make all' would mean 'make E'.  The dependencies would then lead to
>> building modules A, B, C, D, E in this order.
>> If I am in E and call 'make --from C' then only C, D, and E should be
>> built.  A 'make --since C' would only build D and E.
>> If I am in D and call 'make --from B' then modules B, C, and D are built.
>>   Call 'make --since B' to build only C and D.
>> Note that 'make --from' accepts more than one module name (while 'make
>> --all:<module>' does not).
>> Note also that in the above case (stand in D, call 'make --from B') module
>> A is not built, regardless of whether there are changes in A or not.
>>   Whereas a simple call to make (still standing in D) would build all
>> modules that D depends on, directly or indirectly.  Thus the options
>> '--from' and '--since' exist to actively exclude modules from being built.
>> The whole thing becomes a little bit more complicated with multiple
>> options to '--from' (I never use '--since' and also don't know a valid use
>> case so I will ignore it for now) and more complex dependencies then in the
>> simple example above.  Let's say that if we stand in instsetoo_native and
>> call 'make --from svx sfx2'.  Note that svx depends on sfx2.  This would
>> build svx, sfx2 and all modules that depend (directly or indirectly) on svx
>> OR sfx2.
> got it, now I just have one problem, why would you not build the dependent
> modules, if they needed to be built, thats a scenario I dont understand.
> With a central makefile, <module>/makefile will not be called so we do not
> waste cpu cycles.
> With the .done files, we know when a module was last built and all modules
> that depend it should be rebuilt which the rule
> <module>.done : <module_depend>.done
> will ensure, so If we have A -> B -> C -> D
> I go in B, and call make, then when I go in D and make, B,C,D will be made.
> If we have A -> B -> D   C -> D
> and do the same then only D will be made.
> So --from is not really saving anything ?

a) In your example you first go into B then, in a second step, into D.  
The '--from' option lets you do the same (well, not really the same, but 
see below) just from D.

b) You go first to B and call make.  This makes A, if necessary, then 
B.  The making of A is exactly the thing that you want to prevent with 
the '--from' option.  Go into D and call 'make --from B'.  A is not built.

c) After the discussion with you I am not sure if we still need --from 
because the two reasons I know for its existence my not be relevant with 
the new approach.

c1) With the '--from' option you can tweak the dependency rules at 
runtime (a bit).  This allows you to exclude projects from being built 
when you know that that is not necessary.  But from experience I know 
that can lead to very subtle errors.  Letting the system determine what 
to built is usually more reliable.

c2) With a 'build --all' still builds every module on which the 
one you are standing in depends on.  When those modules have been built 
previously, then no compilation takes place.  But calling dmake for a 
couple of directories for close to 200 modules (when you stand in 
instsetoo_native) takes a lot of time (several minutes on Windows), even 
when no file has to be compiled.  This wasteful way of doing nothing can 
be prevented with the --from option.
However, with the new approach and its .done flag files you can 
determine which modules need to be built much faster.  You don't have to 
call dmake on directories that where already built.  Hm, but this again, 
does only work if your .done files have dependencies on all relevant 
source files.   That is something that is missing at least from my script.

So, reasons for the existence of '--from' are a result of old/slow 
computers, slow files systems (still valid on Windows), missing global 
dependencies (which we now have for gbuild) and impatient developers.

>> While this is easy to do with eg Perl I am not sure how to handle this
>> with just a Makefile.  The straightforward approach with handling
>> <module>.done files does not work.  And that is one of the reasons why I
>> don't think that (GNU) makefiles are a good solution for any problem.  Most
>> of us are used to program object oriented/imperative.  Makefiles require a
>> declarative approach. Maybe the use of Perl is not such a bad idea.  Maybe
>> it would be better to reimplement with a lot fewer options and
>> with better readable code.
> I agree that makefiles are nowhere near a good solution to many of these
> problems, but its like windows, I dont like it, but everybody uses it.
> We could easily write a new, that also took care of the local
> makefiles, but our build system would not be in the mainstream, and e.g.
> the distros would not like to integrate AOO.
> I have over the last years followed research in building systems, and there
> are (sadly enough) nobody that tries a real object oriented aproach. Also
> if you look at packages like visual studio, QT, eclipse they all use the
> principle of makefiles with declarative approach.
> So my simple question is, do we want to approach the main road (makefiles
> for unix, visual studio for windows/mac) or do we want to have better but
> non standard system.

Good analysis.  Maybe I should answer with Faust: "Zwei Seelen wohnen, 
ach! in meiner Brust" (two souls alas! are dwelling in my breast).  The 
pragmatist says to use the make.  It is good enough for others, it is 
good enough for use.
On the other hand, when I start a new project I usually start with the 
question of what are the best tools for the problem at hand. And make 
does not seem to be the first or the best answer.  Look at our dmake or 
gbuild system.  Both don't use make in a standard way. gmake even 
defines its own language, object oriented and imperative, on top of the 
GNU make macros.  That is, for me, an act of desperation.
I have made experiments with an alternative approach, a domain specific 
language somewhat similar to Java.  I personally like this approach because
a) it uses the paradigm that I already use when writing C++ code. That 
means that I can apply my existing knowledge to the build process and 
that I don't have to remember all the tricks and pitfalls of makefiles.
b) as expected it was much easier to handle file dependencies and 
parallel processing of build jobs in Java than adding object orientation 
and imperative control flow to makefiles.

If I had the time and if I would be the one working on it then I would 
prefer an non-Makefile approach.  But maybe I am just suffering too much 
from one of the 'three great virtues of a programmer': hubris.

You are the one who leads the build project changes, so you have to 
decide which approach to use.  I am not trying to make your life harder 
(than necessary), I am only trying to point out some of the pitfalls 
that I have encountered in the past.  And to prevent you from removing 
features that I use :-)

> rgds
> jan I.
> Ps. its always refreshing to discuss with you, you often have an
> alternative approach, which is not just a dream but doable.

Thanks. That makes two of us.

Have a nice weekend,

>> -Andre
>>>   --prepare
>>>>      Also one option that is important for our every day work.  Use case:
>>>> You make changes in <module> and are not sure if these changes are
>>>> compatible/incompatible.  To be on the safe side you discard the output
>>>> of
>>>> all depending modules.  To save time you keep the output of all other
>>>> modules.
>>>>      Often used together with '--from' like 'make --prepare --from svx' to
>>>> prepare a build after making changes in svx.
>>>>   Documentation changed, funny thing is that svx does not clear correctly
>>> on
>>> my ubuntu build.
>>>   --since <module>
>>>>      A variant of '--from'.  The only difference is that <module> itself
>>>> is
>>>> not built.
>>>>      If your proposed approach is similar to what my script produces then
>>>> it
>>>> is not too difficult to support --from/--since.  I made some experiments
>>>> in
>>>> this direction but was to lazy to finish them.
>>>>   My approach is very similar, but I failed to see how --since is
>>> supported.
>>> And question is if its real important.
>>>   --job
>>>> --pre_job
>>>> --post_job
>>>>     These are sometimes handy to run a non-standard command for all
>>>> modules.
>>>>   I have added them, they are by the way a good example why we need a
>>> discussion I have never used them.
>>> However maybe the real discussion is "do we want to replace build and have
>>> a main/Makefile instead?"
>>>   - I have not used the rest of the unsupported options and would not miss
>>>> them.  Others may have other sets of options that are important to them.
>>>> Some general remarks:
>>>> - Why keep one makefile per module?  Why not put all the inter-module
>>>> dependencies into one file (like my script does)?
>>>>   Ups, I did not explain that correctly, I propose 1 Makefile
>>> "main/Makefile"
>>> with all inter-module and 1 Makefile "<module>/Makefile" that today just
>>> will call the old makefiles as described in prj/build.lst
>>> - Why not use the oportunity to move (a part of) the build environment out
>>>> of the way to, say, build/ ?
>>>>   You have guessed my next step.
>>>   - How are dependencies between modules handled (just the manual
>>>> dependencies from prj/build.lst or also the file dependencies introduced
>>>> by
>>>> gmake).
>>>>   See doc. on --from. Its done with <module>.done files
>>>   - How is the output of the individual calls to dmake or GNU make
>>>> handled/made accessible.  Ie. if there is a build error, how can I look
>>>> up
>>>> the corresponding build output?
>>>>   see doc. script make_log
>>>   - Are the gmake makefiles included (run in the same process) or is GNU
>>>> make started for them it its own process?
>>>>   For a start they would be called (own process), but its something where
>>> I
>>> have no strong opinions.
>>> Please (just to be sure), this proposal has nothing to do with the
>>> students
>>> work, its simply because I saw a positive discussion on removing
>>> ,
>>> and spent a couple of hours looking at it. If there is a preference not to
>>> remove I will simply forget it.
>>> rgds
>>> jan I.
>>>> Regards,
>>>> Andre
>>>>   It has been roughly tested it, thanks to a clever utility from andre.
>>>>> As discussed contains a lot of options, which need to be
>>>>> considered in a makefile.
>>>>> My suggestion is on
>>>>> build.pl_versus_makefile<http:**//**
>>>>> Build_System_Analysis:build.**pl_versus_makefile<>
>>>>> Please feel free to edit/comment on the page. I have reduced to options
>>>>> a
>>>>> lot, and some of them might be in use.
>>>>> thanks in advance for your comments.
>>>>>   ------------------------------****----------------------------**
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