>>> On 28-11-2010 at 9:10, in message <alpine.deb.2.00.1011272348290.11...@ybpnyubfg.ybpnyqbznva>, "Alan W. Irwin" <ir...@beluga.phys.uvic.ca> wrote: > On 2010-11-28 06:39+0100 Michael Hertling wrote: > >> On 11/27/2010 06:45 PM, Alan W. Irwin wrote: >>> I just discovered that many Linux distros these days use the >>> --as-needed Linux linker option by default. At first glance that >>> option makes a lot of sense since it tends to reduce startup times. >>> But I guess there are some caveats as well which is probably why CMake >>> does not adopt this linker option by default for Linux builds. >>> However, I would at least like to try this option for my own Linux >>> builds without forcing it using target_link_libraries. Is it possible >>> to specify linker options such as --as-needed using environment >>> variables and/or -D options? >> >> On Linux, CMake takes account of the LDFLAGS environment variable >> for the initial configuration of the build directory, so saying >> >> LDFLAGS="-Wl,--as-needed" cmake <path/to/srcdir> >> >> enables "--as-needed" for this build directory - forever. > > Thanks, Michael, that was exactly what I needed. I was completely > unaware that environment variable worked for CMake despite many years > of using CMake on Linux. Is the LDFLAGS environment variable > documented for CMake anywhere? I couldn't find it in the > documentation you get with "cmake --help-full", and it is also not > documented at http://www.cmake.org/Wiki/CMake_Useful_Variables. The > useful environment variables CXXFLAGS, CFLAGS, and FFLAGS that allow > you to specify general compiler flags in a convenient way are > undocumented as well, and that is a real shame. > > Alan > __________________________ > Alan W. Irwin > > Astronomical research affiliation with Department of Physics and Astronomy, > University of Victoria (astrowww.phys.uvic.ca). > > Programming affiliations with the FreeEOS equation-of-state implementation > for stellar interiors (freeeos.sf.net); PLplot scientific plotting software > package (plplot.org); the libLASi project (unifont.org/lasi); the Loads of > Linux Links project (loll.sf.net); and the Linux Brochure Project > (lbproject.sf.net).
Hi Alan, You may find the following links of interest. They discuss the virtues and risks of using --as-needed in the light of underlinking and overlinking; and how to fix broken packages in distributions. http://wiki.mandriva.com/en/Overlinking http://wiki.mandriva.com/en/Underlinking http://www.gentoo.org/proj/en/qa/asneeded.xml Regards, Marcel Loose. _______________________________________________ Powered by www.kitware.com Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Follow this link to subscribe/unsubscribe: http://www.cmake.org/mailman/listinfo/cmake
