[CMake] Re: Parsing cmake command line parameters

[Rodolfo Schulz de Lima]

James Bigler wrote:

> What is it that people want beyond -DBUILD_THIS_THAT_WHATEVER:BOOL=TRUE 
> could provide?
> 
> Do they want: --enable-build_this_that_whatever?


People that work with embedded systems might want a stripped down 
version of a library, for instance. So disabling features might be a 
strong use case.

> I also don't understand why we have to parse the whole CMakeLists.txt 
> structure.  We should treat these command line args like we cache 
> variables like CPack does when you configure different builds.

But in the first time cmake is run, there's no cache and no way to know 
what are the command line parameters. Is must run the whole build to 
know that. So the first time 'cmake . --help' runs, the whole build 
should be parsed and executed.

But... what if we have this extreme case?

IF("${CMAKE_BUILD_TYPE}" STREQUAL "Debug")
      add_command_line_parameter(whatever)
ENDIF()

That is, the parameter is bound to another parameter? It's not 
impossible to imagine a case where each time we run cmake --help, a 
different set of parameters is shown. I know, that's stupid, but corner 
cases usually are...

Regards,
rod