Re: [automake] Dependency question with _LDADD

[Michel Briand]

Peter Johansson <address@hidden> - Wed, 27 Aug 2008 10:50:48 -0400

>Michel Briand wrote:
>>
>>>> ::::::::::::::
>>>> src/lib/Makefile.am
>>>> ::::::::::::::
>>>> # Library: libtraining
>>>> # Generates its own pkg-config definition file
>>>>
>>>> AM_CPPFLAGS = -DLIBRARY_VERSION=\"$(LIBRARY_VERSION)\"
>>>>       
>>> Why not put
>>>  AC_DEFINE([LIBRARY_VERSION], ...)
>>>
>>> in configure.ac, so you don't need the above?  Of course you may want to
>>> use a less generic name, e.g. TRAINING_LIBRARY_VERSION.
>>>
>>> Similar applies to -DPROGRAM_VERSION in src/bin/Makefile.am.
>>>
>>>     
>>
>> OK. That's a lot more concise. But having done this:
>>
>> # Step 1: extract version number from a source file
>> TRAINING_PROGRAM_VERSION=`cat PROGRAM_VERSION`
>>   
>Why do you keep that info in a separate file; why not just:
>
>TRAINING_PROGRAM_VERSION=1.0
>

Because program will evolve, hopefully, independently from the build
system. And as such, the program's version is independent from
configure.ac... So it should be stored in a separate file.

From a beginner's point of view the tutorial should enlighten the
difficult pattern of program versioning. That's more complex but do not
introduce a false pattern more difficult to fix later.

>
>
>> # Step 2: export this variable to Makefile
>> AC_SUBST(TRAINING_PROGRAM_VERSION)
>>   
>and if since you AC_SUBST the variable you could (if it is important) 
>create file PROGRAM_VERSION from a PROGRAM_VERSION.in
>
>Setting the version in configure.ac you can avoid all the headache with 
>setting dependencies correctly, especially for a beginners' template 
>that is not appropriate.
>>
>>> FWIW, you could actually add ../../LIBRARY_VERSION to this variable.
>>>
>>>     
>>
>> Yes, it works well too. I'll have all my dependencies handled that way.
>>
>> But working a little with it, I have one remark: 
>>
>> since, with AC_DEFINE, the version is stored in config.h and that all
>> source files depend on it, all my C files are rebuild (in lib or bin)
>> if I change the version file. The smart dependency is lost. So I'll
>> remove library's and program's versions from config.h and rely on the
>> old define on the command line. That's better for my need. But I wait
>> for you comments/tips on the AC_DEFINE I showed earlier in this mail.
>>
>>   
>Defining the version like that at command line, (as far as I can see) 
>you've lost the dependency, in other words, if you change the version 
>number it will not cause a re-compilation. If you want the smart 
>dependency, you could let aclocal create a version.h (AC_CONFIG_FILES) 
>from a version.h.in and then include version.h in only those c files in 
>which it is needed.
>
>Cheers,
>Peter
>

I'll try that, thank you Peter.

Cheers,
Michel
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