[cmake-developers] Alias targets for 2.8.12

[Brad King]

On 08/01/2013 05:26 AM, Stephen Kelly wrote:
> it would be useful for KDE Frameworks to have ALIAS targets in CMake 2.8.12.
> 
>  http://thread.gmane.org/gmane.comp.kde.devel.core/80233/focus=80247
> 
> I finished the topic and pushed it to next in case it can go into that 
> release. 
> 
> I won't be available most of today to change it if needed, but I can fix it 
> up tomorrow if needed.

The topic looks like a great start.  I won't promise to take it
for 2.8.12 yet but let's proceed with review.

- The documentation in add_library and add_executable lists a bunch
  of things one can't do but not an example of what one can do.
  I think this documentation should have an explicit list of what
  is intended and allowed and then exclude everything else.  That
  way if we missed a use case we can treat it as a bug later and
  add the error case.

- Should add_executable be (dis)allowed to add a library alias,
  and vice-versa for add_library?

- The documentation does not mention that alias targets cannot be
  installed or exported.

- Add more "positive" use cases (or "negative" if not allowed)
  to the test suite:

  - add_custom_command/add_custom_target COMMAND argv0 translation
  - add_test NAME/COMMAND signature argv0 translation
  - generator expression references e.g. $<TARGET_FILE:...> in
    add_test and add_custom_* commands
  - Alias for an object library with $<TARGET_OBJECTS:...>
  - Look for other uses of cmMakefile FindTargetToUse and
    FindTarget; all of them need tests for alias behavior and/or
    should be preceded by !IsAlias checks (many are already done).

- How does this interact with $<TARGET_PROPERTY:NAME>?

- When "if(TARGET xyz)" returns true how can one tell from CMake
  code whether xyz is an alias or a real target?  Can one get the
  real target if it is an alias?

Thanks,
-Brad