| CMP0003 | |
| ------- | |
| Libraries linked via full path no longer produce linker search paths. | |
| This policy affects how libraries whose full paths are NOT known are | |
| found at link time, but was created due to a change in how CMake deals | |
| with libraries whose full paths are known. Consider the code | |
| :: | |
| target_link_libraries(myexe /path/to/libA.so) | |
| CMake 2.4 and below implemented linking to libraries whose full paths | |
| are known by splitting them on the link line into separate components | |
| consisting of the linker search path and the library name. The | |
| example code might have produced something like | |
| :: | |
| ... -L/path/to -lA ... | |
| in order to link to library A. An analysis was performed to order | |
| multiple link directories such that the linker would find library A in | |
| the desired location, but there are cases in which this does not work. | |
| CMake versions 2.6 and above use the more reliable approach of passing | |
| the full path to libraries directly to the linker in most cases. The | |
| example code now produces something like | |
| :: | |
| ... /path/to/libA.so .... | |
| Unfortunately this change can break code like | |
| :: | |
| target_link_libraries(myexe /path/to/libA.so B) | |
| where "B" is meant to find "/path/to/libB.so". This code is wrong | |
| because the user is asking the linker to find library B but has not | |
| provided a linker search path (which may be added with the | |
| link_directories command). However, with the old linking | |
| implementation the code would work accidentally because the linker | |
| search path added for library A allowed library B to be found. | |
| In order to support projects depending on linker search paths added by | |
| linking to libraries with known full paths, the OLD behavior for this | |
| policy will add the linker search paths even though they are not | |
| needed for their own libraries. When this policy is set to OLD, CMake | |
| will produce a link line such as | |
| :: | |
| ... -L/path/to /path/to/libA.so -lB ... | |
| which will allow library B to be found as it was previously. When | |
| this policy is set to NEW, CMake will produce a link line such as | |
| :: | |
| ... /path/to/libA.so -lB ... | |
| which more accurately matches what the project specified. | |
| The setting for this policy used when generating the link line is that | |
| in effect when the target is created by an add_executable or | |
| add_library command. For the example described above, the code | |
| :: | |
| cmake_policy(SET CMP0003 OLD) # or cmake_policy(VERSION 2.4) | |
| add_executable(myexe myexe.c) | |
| target_link_libraries(myexe /path/to/libA.so B) | |
| will work and suppress the warning for this policy. It may also be | |
| updated to work with the corrected linking approach: | |
| :: | |
| cmake_policy(SET CMP0003 NEW) # or cmake_policy(VERSION 2.6) | |
| link_directories(/path/to) # needed to find library B | |
| add_executable(myexe myexe.c) | |
| target_link_libraries(myexe /path/to/libA.so B) | |
| Even better, library B may be specified with a full path: | |
| :: | |
| add_executable(myexe myexe.c) | |
| target_link_libraries(myexe /path/to/libA.so /path/to/libB.so) | |
| When all items on the link line have known paths CMake does not check | |
| this policy so it has no effect. | |
| Note that the warning for this policy will be issued for at most one | |
| target. This avoids flooding users with messages for every target | |
| when setting the policy once will probably fix all targets. | |
| This policy was introduced in CMake version 2.6.0. CMake version | |
| |release| warns when the policy is not set and uses OLD behavior. Use | |
| the cmake_policy command to set it to OLD or NEW explicitly. | |
| .. include:: DEPRECATED.txt |