Re: [eigen] Eigen 3.1 release plans

[Christoph Hertzberg <chtz@xxxxxxxxxxxxxxxxxxxxxxxx>]

On 02.05.2012 11:24, Gael Guennebaud wrote:
> The problem is that I'm pretty sure some users are already using it,
> so we cannot simply remove or rename it. Updating its documentation
> should at least discourage new users to rely on it. For old users I
> see you proposed to raise a warning if EDTRM is defined and add a new
> more explicit token. Perhaps it would be enough to add a warning in
> the release note, which is, I think, what is the most likely to be
> read by developers.

Well, EITHER you decide to support EDTRM (until 4.0), then you will 
first and foremost have to warn __developers who rely on Matrices being 
ColumnMajor__, i.e. basically everyone who uses .data(), Map, etc.
OR you decide to deprecate it, which is best done by actually raising a 
warning during compilation not just a release note. Otherwise, you will 
likely miss some people who have the flag hidden somewhere in their 
build-system or people who at some point start to use third-party 
libraries which define this flag somewhere, thus giving them either 
spurious linker errors or, even worse, subtle undefined behavior.

Surely, it would have been better to deprecate it before releasing 3.0, 
especially, as you promised API stability for 3.x, but it is a hard 
decision for a feature that in itself breaks API compatibility ...

Christoph


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Dipl.-Inf. Christoph Hertzberg
Cartesium 0.049
Universität Bremen
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