[CMake] control dependencies in cmake stage

[Mark Abraham]

Hi,

Sure, this is straightforward to do all at make time, if you're prepared to
find out what the names of the generated files are. They must follow some
pattern ;-). Solutions with make-time globbing are surely impossible, and
Petr's IF idea seems brittle to me.

See (for example)
https://github.com/gromacs/gromacs/blob/master/src/gromacs/CMakeLists.txt#L154.
The idea is that you have some target that does the generation, and you
make the eventual library/executable depend on its output files. The target
that contains the generation command has its own dependencies, so you don't
have to re-generate if those don't go out of date. In that example,
gmx_configure_version_file just wraps configure_file(), which sets up that
dependency chain. You'd need an add_custom_command(), it seems, whose
OUTPUT had the list of generated files. There's no problem to use
add_library() with a file generated in the build tree - just mention it in
an output.

There are several much more complicated examples at
https://github.com/gromacs/gromacs/blob/master/docs/CMakeLists.txt. For
example, we build a gmx binary that writes the same text we display with
"gmx topic -h" instead as topic.rst restructedText, which is then parsed
with Sphinx to produce manpages that go in the tarball via CPack, or to
produce HTML to go on our webpage. Helper scripts mostly live in
https://github.com/gromacs/gromacs/tree/master/cmake

Cheers,

Mark


On Tue, Mar 10, 2015 at 6:06 PM, Tomasz Majchrowski <usenet at majchrowski.de>
wrote:

> (sorry if you received this message twice)
>
> Hi Mark
>
> This is the  set of C++ source code files. This set will be compiled
> during the make stage. Ideally will be to move generation to make stage.
> Unfortunately I don't  know the name of the files that will be generated
> before generation phase occurs.
>
> Therefore I can't use set_source_files_properties( foo.cxx PROPERTIES
> GENERATED true) in cmake stage. Please drop a line if you know how to
> bypass this limitation.
>
> Thanks, Tomasz.
>
> 2015-03-10 7:05 GMT+01:00 Mark Abraham <mark.j.abraham at gmail.com>:
>
>> Hi,
>>
>> What are you generating that must be done at cmake time?
>>
>> Mark
>> On 09/03/2015 5:36 pm, "Tomasz Majchrowski" <usenet at majchrowski.de>
>> wrote:
>>
>>> Hi,
>>>
>>> I'm wondering if there is an easy way to control the dependencies in the
>>> cmake stage. Basically I would like skip execution of some script run over
>>> execute_process in case some input files didn't change.
>>>
>>> The regular way will be to use add_custom_command & add_custom_target
>>> however those required targets, so the make stage.
>>>
>>> Please advice how to proceed in case there is need to control this
>>> already in cmake stage?
>>>
>>> Thanks, Tomasz.
>>>
>>>
>>> --
>>> Pozdrawiam/Best regards/Mit freundlichen Grüßen, Tomasz Majchrowski,
>>> Information Technology and Services Consultant and Contractor
>>>
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>>
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