[CMake] autoheader

[BRM]

Yes, my solution does have a more global variable list. However, I think that in this case it works to your advantage as you only have to build the list once and no one has to explicitly know about each list. This makes using a find function (e.g. FindQt()) easier to write - it just has append to a global list; and its done. Otherwise, you'd have to prove yet-another-parameter to it so it could append to your specific list, but then what if you have more than one list? (e.g. a C header, a CPP header, and a Java header) If you append and pull from a single list, then all three could get all the information from the same run; if otherwise you'd have to provide multiple lists to the various find functions.

The disadvantage with the two lines you proposed is that the builder of the list - everyone entering something into the list - would have to know about the file.
Where as the method I proposed, everyone would just add on to the list - registering to a master list - and then the project designer could pull out what they want.
It has a simplicity to it.

Drawing the line on how 'global' the list is is another question - though I would probably make it only as global as the results of any find function would be. (By this, I mean when moving between CMakeLists.txt input files.)

Personally, I think that if this is going to be done the API needs to be not just clean, but also elegant. Tacking on another variable to pass in one or more lists to every single find function so you can have the definitions is not clean nor elegant. The alternative to allowing Find functions to do the work for you is to have the user define everything themselves - and that will become very messy, very quickly especially once people start pulling in other CMakified projects from other people.

So in this particular case, I think a global list serves the overall need better, and will result a much nicer and easier to use API.

Just 2 cents for the pot

Ben



----- Original Message ----
From: Bill Hoffman <bill.hoffman at kitware.com>
To: BRM <bm_witness at yahoo.com>
Cc: Bill Hoffman <bill.hoffman at kitware.com>; CMake <cmake at cmake.org>
Sent: Tuesday, March 31, 2009 12:26:04 PM
Subject: Re: [CMake] autoheader

BRM wrote:
> How about:
> 
> 
> # Each variable can have a registered filter name - packages/programs/libraries would use their name
> cmake_autoheader_add_variable(has_some_other_package, filter_name)
> # user controls what the output file is
> #     User can generate a C #define method (default method if no language is specified)
> cmake_autoheader(C, path/to/cmake/autoheader_output.h [filter_name_list])
> #    User can generate a C++ const methods
> cmake_autoheader(CXX, path/to/cmake/autoheader_output.hpp [filter_name_list])
> 
> - if filter name list is not provided, all entries are entered into the header file
> - if filter is list is provided:
>      - if name listed and is preceeded by an exclamation (!) then that name is not entered
>      - if name is listed then it is entered
>      - if name is not listed, then it is not entered
> 
> Likely it would be good to have a parameter that would specify the default behavior of the filter list - enter or not enter - for names not listed.
> I think a default of 'not enter' would be good if the list is being provided, and this could be overridden and then the list becomes a 'not enter' list.
> 
> So:
> 
> # package defines its own automatically
> find_package(some package)
>    if (some_package_found)
>        -> cmake_autoheader_add_variable(has_some_package, some_package)
> ...
> # user can add it too
> cmake_autoheader_add_variable(has_some_other_package, some_other_package)
> 
> # user controls what the output file is
> #     User can generate a C #define method (default method if no language is specified)
> cmake_autoheader(C, path/to/cmake/autoheader_output.h some_other_package)
> #    User can generate a C++ const methods
> cmake_autoheader(CXX, path/to/cmake/autoheader_output.hpp some_package)
> 
> 
> just another 2 cents...
> 
I am not sure where things would be stored in this API?  Seems to global

Maybe the autoheader should be some sort of target...

cmake_add_autoheader(C /path/to/cmake/autoheader_output.h)
cmake_add_autoheader_variable(/path/to/cmake/autoheader_output.h VAR)


-Bill