On 01/29/2014 09:22 AM, Brad King wrote: > I explained here: > > http://www.cmake.org/pipermail/cmake-developers/2014-January/009487.html > > how the '$' in a value changes some core logic from a short-circuit > to a complex evaluation. However, the question now is why does this > one COMPILE_DEFINITIONS property value get evaluated so many times > that it becomes so noticeable. > > How many directories (add_subdirectory) and targets (add_library or > add_executable) does the project have?
To follow up here, we managed to find the reason the '$' makes things so slow. It can actually happen with only a single evaluation. The problem is the value ends up being appended to a very large string (a list of include directories) and then passed through a macro argument. Since macros re-parse their arguments the large string goes through ExpandVariablesInString and is very slow now that the '$' prevents use of the fast-path. There is separate ongoing work to improve the ExpandVariablesInString slow-path performance, but for now we managed to solve the problem for this Qt4 case with a simple change: Qt4Macros: Make QT4_CREATE_MOC_COMMAND a function http://cmake.org/gitweb?p=cmake.git;a=commitdiff;h=7beba986 -Brad -- Powered by www.kitware.com Please keep messages on-topic and check the CMake FAQ at: http://www.cmake.org/Wiki/CMake_FAQ Kitware offers various services to support the CMake community. For more information on each offering, please visit: CMake Support: http://cmake.org/cmake/help/support.html CMake Consulting: http://cmake.org/cmake/help/consulting.html CMake Training Courses: http://cmake.org/cmake/help/training.html Visit other Kitware open-source projects at http://www.kitware.com/opensource/opensource.html Follow this link to subscribe/unsubscribe: http://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
