[CMake] library path stripping

[Andreas Pakulat]

On 08.06.11 20:00:54, Andreas Naumann wrote:
> Am 08.06.2011 15:02, schrieb Eric Noulard:
> >2011/6/8 Andreas Naumann<Andreas-Naumann at gmx.net>:
> >>Am 08.06.2011 11:56, schrieb Eric Noulard:
> >>>2011/6/8 Andreas Naumann<Andreas-Naumann at gmx.net>:
> >>>
> >>>>Hi @all,
> >>>>
> >>>>I have some problem with the library usage in cmake.
> >>>>
> >>>>It seems to me, that cmake removes the full path of the library, if the
> >>>>path
> >>>>is in the environment variable LIBRARY_PATH.
> >>>>This behaviour cause problems at our system, such that the linker links
> >>>>against the wrong library.
> >>>>
> >>>>Is there an option to avoid this splitting?
> >>>>
> >>>Did you read that:
> >>>http://www.cmake.org/Wiki/CMake_RPATH_handling
> >>>
> >>>Which version of CMake are you using?
> >>>On which system ?
> >>>
> >>>
> >>>
> >>We are using version 2.8.2 and 2.8.4 on Debian and Suse Linux.
> >>
> >>I've read the hints on RPATH handling, but there it is said, that:
> >>"By default if you don't change any RPATH related settings, CMake will link
> >>the executables and shared libraries with full RPATH to all used libraries
> >>in the build tree"
> >Yes.
> >And you did not mention it but the probleme you have occurs when using
> >the executable **directly from the build dir** right?
> what do you mean with "using"? I cannot even link the executable,
> because cmake removes the path from the library without adding the
> directory to the library directories.
> 
> >>This means, if I don't set anything related to RPATH, cmake should not strip
> >>the path from the library, should it?
> >No it shoudn't for the binary in the buitd tree but...
> >if you do "make install" the installed binaries will have no RPATH unless
> >you set
> >
> >SET(CMAKE_INSTALL_RPATH "${CMAKE_INSTALL_PREFIX}/lib")
> >
> ># add the automatically determined parts of the RPATH
> ># which point to directories outside the build tree to the install RPATH
> >SET(CMAKE_INSTALL_RPATH_USE_LINK_PATH TRUE)
> >
> I don't even want to install, just build and use.
> >>I played with the example and it was a bit hard to understand, when the path
> >>is stripped from the library.
> >>The problem arises before linking the executable.
> >This is a different issue.
> >Could you copy/paste the
> >
> >add_executable
> >and
> >target_link_libraries
> >
> >statement you use for the offending executable?
> >
> simple:
> project("test")
> 
> cmake_minimum_required(VERSION 2.8)
> set(MYLIB /home/andreas/cmake_test/lib/libfoo.so)
> add_executable(foo_exec test.cc)
> target_link_libraries(foo_exec ${MYLIB})
> 
> So the executable gets the full name and the example works, if the
> environment variable library_path is not set to
> /home/andreas/cmake_test/lib. The link command is:
> 
> /usr/bin/c++      CMakeFiles/foo_exec.dir/test.cc.o  -o foo_exec
> -rdynamic /home/andreas/cmake_test/lib/libfoo.so
> -Wl,-rpath,/home/andreas/cmake_test/lib
> 
> If I set LIBRARY_PATH to /home/andreas/cmake_test/lib, the directory
> is stripped and the link-command gets:
> 
> /usr/bin/c++      CMakeFiles/foo_exec.dir/test.cc.o  -o foo_exec
> -rdynamic -lfoo

I can reproduce this here with CMake 2.8.4.

And before someone else asks (since I thought that might be the error),
the envvar is really "LIBRARY_PATH", i.e. not LD_LIBRARY_PATH.

The strange thing is that there's no occurrence of this specific string
anywhere in the cmake sources. There are all kinds of occurrence of
LD_... or CMAKE_... but no string matching just LIBRARY_PATH. So its
unclear why CMake respects that envvar.

Andreas