[cmake-developers] Function overrides

[Wojciech Knapik]

On Thu, May 30, 2013 at 10:16:47PM +0200, Wojciech Knapik wrote:

> On Thu, May 30, 2013 at 08:01:16PM +0200, Wojciech Knapik wrote:
> 
> > On Thu, May 30, 2013 at 11:39:01AM -0400, Brad King wrote:
> > 
> > > On 05/30/2013 11:14 AM, Wojciech Knapik wrote:
> > 
> > > > PS. I know you can achieve this by providing a wrapper for the
> > > > user to use instead of the standard function, but that's not
> > > > nearly as nice, is it ?
> 
> Since I'm likely not getting any further with the function overriding
> issue, I'm thinking of other ways to do this, but they're all bad.
> 
> Let's say I'd like to write two unrelated modules, that provide some
> functionality related to add_executable(). I could just provide a
> function to call in addition to add_executable(). This would require
> modifying all the CMakeLists calling that function and adding the call
> to the one the module provides. That's not DRY, since I could just
> call one function that calls the two. So, to remove this problem, I
> create a wrapper in the module, that calls add_executable() and my
> function.  Let's call it add_foo_executable() (provided by module
> foo). So I edit all the CMakeLists and substitute occurrences of
> add_executbale() with add_foo_executable(). That could be hundreds of
> changes, but let's say for now this is ok. Then I include the second
> module bar, that also provides a function and a wrapper. I can't use
> the new wrapper, because I already use the old one. I can't fuse the
> wrappers together, so the only way out is to create a third wrapper
> outside both of these modules, that calls add_executable() and the two
> functions provided by the two modules. That sort of works, but now I
> have to edit all the CMakeLists again and I've effectively coupled my
> code and the two modules together.  But let's say for now, that that's
> not wrong in any way.
> 
> A few months pass, a few more modules get written and it all turns out
> to work quite nicely, so I decide to publish them as open source, for
> everyone's benefit. How do I distribute these modules and allow people
> to use any combination of them ? Do I create a separate wrapper for
> every combination ? Do I create a series of if(COMMAND ...) in the one
> wrapper ? Where do I define that wrapper ? If I put it in each of the
> modules (wrapped in if(NOT COMMAND ...)), that's copy-pasting code, if
> I create a third module with just that function, the modules are no
> longer standalone.
> 
> There's no good way out of this.  Or I don't see one.  Which is it ?

I good really use some guidance on this. Anyone care to comment ?

WK