[cmake-developers] A policy for Policies

Stephen Kelly steveire at gmail.com
Sat Jun 6 10:16:18 EDT 2015


Alex Merry wrote:

> I'm not sure the term REQUIRED_IF_USED is clear enough - I'm certainly
> confused by quite what you mean by it.

You'll find it if you grep for it in cmake.git.

> The main reason for keeping policies around, as I see it, is to allow old
> projects to keep building with newer versions of CMake.

Actually the reason is to give projects notification and time to port to the 
NEW behavior, while also making it possible for them to get OLD behavior if 
they are close to their own release and can't port at that time.

Setting a policy to REQUIRED_IF_USED in the cmake source means that if 
someone tries 

 cmake_policy(SET CMP0011 OLD)

they will get an informative error instead of no warning.

Thanks,

Steve.




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