[CMake] Best way to handle application data path for local run vs. installation

[Dmitry Marakasov]

Hi!

This question bugs me for a long time so I though maybe someone has
a solution. I have a project which includes an application and some
data for it. An application needs to know path to its data files, so
I pass it via compiler definition: ADD_DEFINITIONS(-DDATADIR="...")

The problem is that this path is different based on whether I want to
run the application from build directory:

ADD_DEFINITIONS(-DDATADIR="${PROJECT_SOURCE_DIR}/data")

or want to install it systemwide:

ADD_DEFINITIONS(-DDATADIR="${CMAKE_INSTALL_PREFIX}/share/myapp")

I want my project to both run from build directory and to be
installable systemwide, without the need to rebuild or specify extra
options.

- I don't want to make an applications search for its data relative
  to executable path
  - There's no cross-platform way to get an executable path
  - This will break when executable is moved or hardlinked
- I don't want to try both paths, as this is error prone, as installed
  executable may pick data files from repository or vice versa
- I don't want to make user specify additional cmake flags like
  -DSYSTEMWIDE_INSTALLATION or -DRUN_LOCALLY.
- I don't want to use any wrapper scripts
- I don't want to build two executables

The best solution would be for cmake to fix path in executable file
right after installation, something similar to what cmake does with
rpaths. Or there could be a cross-platform way for executable to know
whether it was installed which I've missed.

Any ideas?

-- 
Dmitry Marakasov   .   55B5 0596 FF1E 8D84 5F56  9510 D35A 80DD F9D2 F77D
amdmi3 at amdmi3.ru  ..:  jabber: amdmi3 at jabber.ru      http://amdmi3.ru