[cmake-developers] New OBJECT library feature

[Eric Noulard]

2012/3/19 Brad King <brad.king at kitware.com>:
> Hi Folks,
>
> I've just pushed a new 'object-library' topic and merged to 'next'
> for testing.  David Cole and I have been working on it for a couple
> of weeks.  The following documentation added to the add_library
> command explains:
>
> --------------------------------------------------------------------------
>  The signature
>
>   add_library(<name> OBJECT <src>...)
>
>  creates a special "object library" target.  An object library compiles
>  source files but does not archive or link their object files into a
>  library.  Instead other targets created by add_library or
>  add_executable may reference the objects using an expression of the
>  form $<TARGET_OBJECTS:objlib> as a source, where "objlib" is the
>  object library name.  For example:
>
>   add_library(... $<TARGET_OBJECTS:objlib> ...)
>   add_executable(... $<TARGET_OBJECTS:objlib> ...)
>
>  will include objlib's object files in a library and an executable
>  along with those compiled from their own sources.  Object libraries
>  may contain only sources (and headers) that compile to object files.
>  They may contain custom commands generating such sources, but not
>  PRE_BUILD, PRE_LINK, or POST_BUILD commands.  Object libraries cannot
>  be imported, exported, installed, or linked.

That's a great feature.
This would be useful for cross-compiled  target.

Is there a feature that could guarantee the order of appearance of
those objects / object library on the link line generated for
add_executable ?

By the way why wouldn't you authorize
target_link_libraries(exetarget objlibname) ?


> --------------------------------------------------------------------------
>
> Many of the documented restrictions are temporary until meaningful
> behavior can be defined and implemented for them in a future version.
> It is easiest to simply disallow all but the basic use case for now.

Ok this answers my previous question.

> This feature plays a role similar to autotools convenience libraries
> but works with all toolchains and under VS and Xcode.  We've updated
> all primary generators to support object libraries including the Ninja
> generator.  Until this goes into master watch out for conflicts when
> making changes to the other generators.
>

I'll test the feature.
-- 
Erk
Le gouvernement représentatif n'est pas la démocratie --
http://www.le-message.org