| 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 |