Versioning best practices

[Thomas Kuehne]

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Lars Ivar Igesund schrieb am 2007-01-24:
> I've been looking at what D and the compilers provide to help with
> successfully versioning D source code in such a way that it minimizes
> duplication of code (and in the process ease organization of said code),
> ease readability and ease building.
[...]
> Do you think that the current tools are adequate?

Most of the times versioning is the wrong approach. I think C's
(and to a lesser extend C++'s) non-existing compile time reflection
forced everyone to use versioning instead of "featuring".

I'll use Flectioned[1] as a sample.

the problem: support 5 different D APIs
* dmd-1.001
* dmd-1.00
* dmd-0.177
* gdmd-0.21
* gdmd-0.20
("Normal" programs shouldn't notice the differences, they are however
crucial for Flectioned.)

the solution:
* targeted operation system / binary format
# flectioned.d:755: version(linux){

* new GC features
# flectioned.d:495: static if(is(typeof(si.flags)))

* changed member names for some TypeInfo classes
# flectioned.d:1443: static if(is(typeof((new typeof(ti)()).value)))

The rest is done with generic logic that handles issues like mangling
bugs without requiring "static if" or "version".

Thomas

[1] runtime reflection for D:
http://svn.dsource.org/projects/flectioned/downloads/flectioned.zip

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