2012/6/14 Daniel Pfeifer <dan...@pfeifer-mail.de>: > 2012/6/14 David Cole <david.c...@kitware.com>: >> Sounds awesome to me! >> >> When can you submit a patch? :-) >> > > Thanks for the motivation! While I would like to contribute a patch, I > have absolutely no idea where to start. > Should it go to cmAddExecutableCommand.cxx and > cmAddLibraryCommand.cxx? Or rather directly to the generator(s)? > > Given that the required changes are probably very small (the > implementation that I linked above is less than 100 lines of CMake > code), it is maybe more effort for you to get me started than it is to > implement it... :-)
David, did you decide whether you want to implement that feature by yourself or give me an introduction to the CMake architecture? Where can I find more help? I am a little lost between global and local generators. cheers, Daniel >> On Thu, Jun 14, 2012 at 4:36 AM, Daniel Pfeifer <dan...@pfeifer-mail.de> >> wrote: >>> >>> Hi, >>> >>> In a private mailing with Dave Abrahams and Brad King I wrote a >>> proposal of how I imagine PCH support should be implemented. Brad >>> asked me to send it to this list for further discussion. >>> Please note that even though I use present tense in the proposal, >>> nothing descibed below is implemented yet. >>> We have a similar implementation for PCH [1], but the interface >>> differs to this proposal. >>> >>> [1] >>> https://github.com/ryppl/ryppl/blob/develop/cmake/Modules/RypplPrecompileHeader.cmake >>> >>> cheers, Daniel >>> >>> >>> >>> CMakeLists.txt changes >>> ---------------------- >>> There are new target properties PRECOMPILE_HEADER and >>> PRECOMPILE_HEADER_<config>. These properties may be set to a list of >>> header files: >>> >>> set_property(TARGET target APPEND PROPERTY PRECOMPILE_HEADER >>> <boost/spirit/karma.hpp> >>> "my/precompiled/header.h" >>> ) >>> >>> >>> changes to source files >>> ----------------------- >>> None. All source files should be written as if there was no PCH >>> support. That means that each file should include all the headers it >>> requires. Nothing more, nothing less. >>> >>> That especially means that source files should *NOT* include an >>> "all.h", "precompile.h", or "stdafx.h" file. Nothing breaks if they >>> do, but it may impact compile times if precompiled headers are not >>> supported. >>> >>> >>> file(s) to precompile >>> --------------------- >>> Special header files that contain all the system headers may be >>> created and added to the PRECOMPILE_HEADER property. However, the >>> system headers may also be added directly to PRECOMPILE_HEADER. >>> >>> If custom files are created, it is important to note that a special >>> PCH_SUPPORTED guard is *NOT* required. >>> >>> >>> What is done behind the scenes >>> ------------------------------ >>> CMake creates the actual header file that is going to be precompiled >>> during the config step inside the current binary directory. The >>> complete filename encodes the target name and the configuration (eg. >>> "${CMAKE_CURRENT_BINARY_DIR}/${target}_${config}_pch.hpp") and >>> contains one #include directive for each element in the >>> PRECOMPILE_HEADER/PRECOMPILE_HEADER_<config> list. If the element is >>> wrapped in angle brackets, it is included unmodified, otherwise the >>> *absolute path* is used in double quotes. The generated header file >>> for the above example may look like this: >>> >>> /* generated by CMake 2.8.x */ >>> #include <boost/spirit/karma.hpp> >>> #include "/home/daniel/workspace/foo/my/precompiled/header.h" >>> >>> >>> This header file is compiled before all object files of the target; ie >>> the object files depend on the compiled header. >>> >>> >>> MSVC specific >>> ------------- >>> MSVC requires a source file to compile the header. This source file is >>> generated by CMake alongside the header file and may be called >>> <target>_pch.cpp, for example. It contains just one line: an #include >>> directive that includes the configured header file. >>> >>> The precompiled header (pch_binary) is created by compiling the source >>> file (pch_source) with "/Yc\"${pch_header}\" /Fp\"${pch_binary}\"". >>> >>> For the MSVC IDE, pch_binary might be "$(IntDir)/${target}.pch". >>> >>> All other source files are compiled with "/Yu\"${pch_header}\" >>> /FI\"${pch_header}\" /Fp\"${pch_binary}\"". >>> >>> /Yc = create pch >>> /Yu = use pch >>> /FI = force include >>> /Fp = name pch binary >>> >>> >>> GCC specific >>> ------------ >>> In GCC the pch_binary is created by compiling the header file directly >>> (no extra source file is required). The pch_binary must be >>> "${pch_header}.pch", there is no way to change that. Here, it pays off >>> again that we generate the actual pch_header in the binary directory. >>> >>> The compile flags to compile the header are "-x c++-header" and the >>> output file must be set with "-o ${pch_binary}" >>> >>> All the other source files are compiled with "-include ${pch_header}" >>> (force include), it may also be a good idea to pass "-Winvalid-pch". >>> -- >>> >>> 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://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers >> >> -- 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://public.kitware.com/cgi-bin/mailman/listinfo/cmake-developers
