Generating a proprietary version list

Usage
1

Hi,

in a cmake project several sub directories have project()s with different proprietary version numbers. We are using a macro called by each affected CMakefile.txt like ARTEFACT_VERSION(“NAME” “1.2.3”). This writes a file artvers.txt with all the name=version entries by appending. To avoid duplicates on next run, there is a heuristic deleting the file first. It is important to see that currently the main project files that use this (indirectly) by add_subdirectory() do not handle any of that. Just by using at least one sub project that has a artvers.txt entry, the file currently gets created automatically.
It works, however, I cannot sort the entries, duplicate names lead to bad error behavior and the deletion mechanism does not feel to good.

But how to do it better/right?

I’m re-implementing the macro to not directly write to the file, but actually add to a global property (list). With a second marco the list is sorted and written by file(GENRATE). This works fine so far. My problem now is that I would need to call the second macro, the actual write, from every top level CMakefile.txt (and I may not even know all of them, there are quite a few, metrics talk about ~50.000 lines cmake files).

So I’m looking for a way to “register” a creation in first call of the ARTEFACT_VERSION() macro, but execute after all CMakefiles have been processed.

What I tried:
I cannot use file(GENRATE) with a variable, because apparently the variable is evaluated at call of file(GENERATE), not at time of actual generation (so it includes only the first artvers.txt entry). I cannot specify to use a global property in file(GENERATE). Then I tried custom_command()s (I have a hook available to make it run, I have a general target were I can add this as dependency), but only got some messy intermediate results; generating multiline files seems to make it ugly. Seems not to be the way either.

Now I wondering how to approach this correctly. There seems to be a mechanism where all this works, the @REPL@ mechanism, but I don’t know how to utilize that in my case.

I hope I explained well and someone can point me to the right direction.

Thanks for reading all this :slight_smile:

2

Check out cmake_language(DEFER ... CALL ...) (docs). You can use that to run something at a later point, including by specifying a directory scope in which the call should run. For example, the following would print a message at the end of the top level CMakeLists.txt:

cmake_language(DEFER
    DIRECTORY ${CMAKE_SOURCE_DIR}
    CALL message "This is the end of the top level CMakeLists.txt"
)

The command also supports options for associating an ID with the deferred command. You could potentially use that to only add the deferred command once, or you could just set a global property with a well known name (but make that name specific to your organisation to avoid clashes with other project’s names).

3

Thank you so much for pointing me to this nice feature!
(Unfortunately it is not available in the cmake-3.18 used by the project and apparently I cannot convince to update)