[CMake] Cmake absolute paths with gcc, __FILE__ , and logging

[Willy Lambert]

Hi all,

Short Story :

I am trying to convert an existing project from Manual Makefiles to
Cmake for building it.
We have a logger that rely on the __FILE__ define to say which file is
"writing" into the log but this is broken by the CMake default
behavior using absolute paths.
So I wonder if there is any way to have the file name in the code to
be able to log "Error : line XXX in file.cpp".




Long Story :



So I have for instance a source /home/me/src/main.cpp, compiled with
relative paths "gcc -o main.cpp".
So the logger say  "Error : line XXX in main.cpp".

Going further, if I have a file "dummy.hpp" included from main.cpp
that have for any reason an inlined function that log something, it
will say "Error : line YYYin dummy.hpp" from main.cpp. This is due to
the fact that gcc plays with __FILE__ behind the scene.

What defines the __FILE__ value is the path given to the preprocessor
(so the one given to gcc, so the one given by the makefile generated
by CMake). So now I have something like :
"Error : line XXX in /home/me/src/main.cpp"
which is very anoying because :
1/ it reduces lisibility
2/ it show a wrong path when the project is on another machine.


I tried to use the suggested trigger "set_source_files_properties" to
define my own __FILE__ but it doesn't works with included files (it
shows main.cpp instead oh dummy.hpp)
http://www.cmake.org/pipermail/cmake/2011-December/048281.html

So this way is a dead end because the compilator (and the one that
creates its command line)  is the only one to be aware of this
information.

Beside that, as I would really like to simplify the "VERBOSE=2 make"
output to be able to debug what CMake generates I currently have
plenty of path with 20 or more folder level including many "../..", I
am looking on making CMake giving relatives paths to gcc.

I have seen some thread about the use of CMAKE_USE_RELATIVE_PATHS, but
it seems that it is not working, and maybe with no will to support
this (is that true ?)
http://cmake.3232098.n2.nabble.com/CMAKE-USE-RELATIVE-PATHS-td4042914.html

Does anyone have succeeded with relatives path in CMake ?