[CMake] Supporting large numbers of projects

[Bill Hoffman]

KSpam wrote:
> My company is using CMake to build a large number of projects (~300).  The 
> developers have complaints regarding the size (and load-time, etc) of the 
> top-level solution file.  I am attempting to address their concerns.
> 
> Take this hypothetical project hierarchy:
> 
> module-1/
> 	sub-module-1/
> 		project-1
> 	...
> 	sub-module-n/
> 		project-n/
> ...
> module-n/
> 	sub-module-1/
> 		project-1/
> 	sub-module-n/
> 		project-n/
> 
> In Linux, I can simply change to module-1/sub-module-1/project-1 and build 
> from there.  Any dependencies of the project will automatically be built as 
> well.  Unfortunately, this does not work with Visual Studio on Windows.  On 
> Windows, the dependencies are not automatically built when opening up a lower 
> level solution file.  Will this be addressed in CMake 2.6?
> 
> One option I have given to the users is the ability to switch between source 
> and binary modules or sub-modules.  For instance, the project would have the 
> following options:
> 
> MY_BUILD_module-1:BOOL
> MY_BUILD_sub-module-1:BOOL
> ...
> MY_BUILD_module-n:BOOL
> MY_BUILD-sub-module-n:BOOL
> 
> When all of the projects are built, I can manually switch off the build 
> options for some of the modules and sub-modules.  This allows us to create 
> partial-source deliverables to customers (i.e. module-1 is delivered as 
> headers and libs, and module-n is delivered as source).  This also reduces 
> the complexity of the top-level solution file.  Additionally, this allows us 
> to build sets of code against tagged release binaries.
> 
> To accomplish this scheme, I have to manipulate "*_LINK_TYPE", "*_LIB_DEPENDS" 
> variables for modules and sub-modules that are turned OFF (I am using 
> INTERNAL CACHE variables for this).  I found that I have to configure twice 
> prior to generating the build files any time a "MY_BUILD_*" option is 
> toggled.
> 
> Ideally, I would like a way to prevent the generation of the build files until 
> the second configure completes.  Is there a way for me to accomplish this?
> 

If you use the project command in each sub project cmake 2.6 will do the 
right thing and create sub-solutions that include all targets that they 
use in the larger project.

-Bill