On Sep 26, 2008, at 2:28 PM, Bill Hoffman wrote:

Mike Jackson wrote:
I started noticing some warnings when I am linking my project executables that bascially says libraries are listed multiple times on the link line. Now this is just a warning so I _could_ ignore it but I am curios about how cmake is working at this point. Here is what I have:
Library MXADataModel built by CMake.
It depends on Expat, Tiff and HDF5 (which are installed on the local filesystem and NOT build by cmake). I have some Examples that are built in the same project as the MXADataModel library. Lets take one of those examples as and "example"..
SET (DATAIMPORT_EXAMPLE_SOURCES
${MXA_SOURCE_DIR}/src/Examples/DataImport/main.cpp
${MXA_SOURCE_DIR}/src/Examples/DataImport/SimpleImportExample.cpp
${MXA_SOURCE_DIR}/src/Examples/DataImport/ExampleImportDelegate.cpp
${MXA_SOURCE_DIR}/src/Examples/DataImport/ ExampleImportDelegateFactory.cpp
)
SET (DATAIMPORT_EXAMPLE_HEADERS
 ${MXA_SOURCE_DIR}/src/Examples/DataImport/SimpleImportExample.h
 ${MXA_SOURCE_DIR}/src/Examples/DataImport/ExampleImportDelegate.h
${MXA_SOURCE_DIR}/src/Examples/DataImport/ ExampleImportDelegateFactory.h
)
source_group(src\\Examples\\DataImport FILES $ {DATAIMPORT_EXAMPLE_SOURCES} ${DATAIMPORT_EXAMPLE_HEADERS})
ADD_EXECUTABLE(DataImportExample ${DATAIMPORT_EXAMPLE_SOURCES})
TARGET_LINK_LIBRARIES(DataImportExample ${MXADATAMODEL_LIB_NAME} )
MXADATAMODEL_LIB_NAME is the name of the MXADataModel library that is built earlier in the project and has dependencies on hdf5, tiff and expat. If I use the code as is then cmake will actually add the tiff, hdf5 and expat libraries to the link line. Is CMake _supposed_ to do that? This is building shared libraries and tiff, expat and hdf5 are all dylibs also. Building MXADataModel as a static library shows the same behavior. This is on OS X 10.5.5 with Xcode 3.1.x tooling generating Makefiles. Same thing using Xcode generated targets. So maybe I just don't understand how linking works on OS X? Just wondering if I make changes to the CMake files will it mess up windows builds?
Yes, cmake automatically chains this stuff.

add_library(a ...)
target_link_library(a b c)

add_executable(foo ...)
target_link_libraries(foo a)

This will cause foo to link to a b c.

With CMake 2.6.2 you can stop this from happening with a target property:

http://www.cmake.org/cmake/help/ cmake2.6docs.html#prop_tgt:LINK_INTERFACE_LIBRARIES

-Bill

And just to be clear this will work on all platforms, all compilers?

Mike.

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