[CMake] Re-executing CMake from the Makefile.

[Bill Hoffman]

Óscar Fuentes wrote:
> Bill Hoffman <bill.hoffman at kitware.com>
> writes:
> 
>> Óscar Fuentes wrote:
>>> Currently, when `make' is executed and a CMakeList.txt file is out of
>>> date, `cmake' is automatically invoked and then `make' continues. Is it
>>> possible to do this (on a reliable way) with an arbitrary file?
>>>
>>> I need to re-execute `cmake' whenever certain file changes. I wonder if
>>> is possible to do this from `make' itself, so the user does not need to
>>> remember that he must execute `cmake' first.
>>>
>> If the file you depend on is part of the input to cmake then cmake
>> will do that automatically.  You could use the configure_file command
>> to do this.  If you did something like this:
>>
>>  configure_file(/my/file/input dummyout)
>>
>> Then when ever /my/file/input changed cmake would re-run at make time.
> 
> Will this work if /my/file/input is the output of some intermediate
> `make' execution?
> 
> I mean:
> 
> $ make  # invoke make, which may modify /my/file/input at some point
> 
> Will `make' invoke `cmake' on the fly and keep running with the new
> makefiles regenerated by `cmake'?
> 
> If this is not possible, I would like to stop `make' when
> /my/file/output changes, possibly showing some message to the user
> instructing him to invoke `make' again.
> 
You could just return an error code from the command that builds the 
/my/file/output, that should stop make from running.

> All this is because /my/file/input actually is an script that is used
> for determining which libraries the executables depends on. The current
> build system builds the libraries, then the script and finally the
> executables. As initially it is impossible for `cmake' to stablish
> dependencies between libraries and executables, I wish the build to stop
> or restart once the script is built and re-execute cmake so it can use
> the script for inquiring what the dependencies are, re-generate the
> makefiles and continue the build.
> 

Why does the script need to be constructed at make time?  Seems like you 
could push a bit more of the work into the script itself and all should 
be good.

-Bill