I would like to pass some options to a compiler. The option would have to be calculated at compile time - everytime when 'make' is invoked, not when 'cmake', so execute_process command does not cut it. (does it?)
For instance passing a date to a g++ compiler like that:
g++ prog.cpp -o prog -DDATETIME="17:09:2009,14:25"
But with DATETIME calculated at compile time.
Any idea how to do it in CMake?
Bounty edit:
A least hackish solution will be accepted.
Please note that I want to be able to exectue an arbitrary command at compile time, not only 'date'.
Edit 2:
It have to work on Linux, Windows (VS), Mingw, Cygwin and OS X. You can't assume Ruby, Perl or Python as they are non standard on Windows. You can assume BOOST, but I guess it's no use.
The goal is to force cmake to generate Makefile (in case of Linux) that when make is executed, will do the job.
Creating custom *.h file is ok, but it has to be initiated by a Makefile (or equivalent on other OS) by make. The creation of *.h doesn't have to (and shouldn't have to) use cmake.