[CMake] patch on Windows

[Nils Gladitz]

On 12.01.2014 01:39, Rob McDonald wrote:
> Where does CMake get its patch implementation?

As far as I know CMake does not have a patch implementation.

>
> I'm using a patch step with ExternalProject_Add on Windows (and other 
> platforms).
>
> I had it working on one Windows machine - which unfortunately just got 
> knocked off a desk and will never be recovered.  The same files on a 
> different Windows machine doesn't work.
>
> 'patch' is not recognized as an internal or external command.
>
> Looks like CMake can't find 'patch', but I thought it was built-in.  I 
> was using 2.8.8, but when I ran into this, I upgraded to 2.8.12.1 -- 
> no change.

I think if your PATCH_COMMAND literally contained "patch" (without path) 
the only way it was working before is that it was somewhere in your PATH 
environment.

> Is there a FindPATCH.cmake I need to use?  For Windows patching, am I 
> better off just carrying new copies of the changed files and copying 
> them over in the patch step?

I don't think cmake provides a FindPATCH.cmake but there wouldn't be one 
to be found per default on a standard windows installation either.
The PATCH_COMMAND can be anything. For something portable I'd try to 
stick to "${CMAKE_COMMAND} -E" (command mode) or "${CMAKE_COMMAND} -P" 
(script mode).
-E provides copy commands while -P would allow you to read and write 
files and perform e.g. regular string or regexp substitutions.

Nils