[cmake-developers] Splitting roles of CMAKE_INSTALL_PREFIX

[Stephen Kelly]

Brad King wrote:
> Both roles are already widely used.  There is user code that:
> 
> * Sets CMAKE_INSTALL_PREFIX to change the install dest (role 1).
> * Uses CMAKE_INSTALL_PREFIX as the target install dest (role 2).
> 
> Moving one role into a separate variable will require user code for
> at least one of the two roles to be updated to support the case
> when the values are different.  Role 2 is probably more common.

In cmake code you mean? I imagine there are lots of bash scripts or aliases 
which invoke cmake with -DCMAKE_INSTALL_PREFIX (I use an alias).

> We've split variables like this before.  When cross compiling was
> first added CMAKE_SYSTEM_NAME was kept as the target and a new
> CMAKE_HOST_SYSTEM_NAME variable was added for the host.  For
> consistency with that approach perhaps your proposed variable
> CMAKE_HOST_INSTALL_PREFIX could take over role 1 when set.
> 
> Thoughts?

I think CMAKE_EXTERNAL_INSTALL_PREFIX would be a better name. 

I'd prefer the ability to make CMAKE_HOST_INSTALL_PREFIX mean 'the location 
to install host tools when doing a HOST+TARGET build' in the future.

Thanks,

Steve.