Le Tue, 16 Dec 2008 12:26:26 -0800, Tyler Roscoe <ty...@cryptio.net> a écrit :
> I am using what I think is a common pattern to create some headers. > Following the example at > http://www.cmake.org/Wiki/CMake_FAQ#How_do_I_generate_an_executable.2C_then_use_the_executable_to_generate_a_file.3F, > I have an add_custom_command which calls a script (generateheader.py): > > add_custom_command ( > DEPENDS generateheader.py > OUTPUT results/header.h > COMMAND ${PYTHON_EXECUTABLE} > ARGS generateheader.py --infile=src/header.in.h > --outfile=results/header.h ) > > And then I have an add_custom_target to wrap the command in a target: > > add_custom_target ( > generateheader ALL > DEPENDS results/header.h > ) > > This seems to mostly do what it's supposed to do. When I run "make > all", the generateheader target runs and results/header.h is created. > When I run "make generateheader", same thing. > > So now the problem. > > When I do "make all", the generateheader target *always* runs, even if > results/header.h and generateheader.py are up-to-date. > > This is a problem because other targets depend on generateheader, so > when generateheader runs, all the dependent targets also run. This > makes it impossible for me to do a delta build. > > Some closer reading of the manual suggests that this is by design. > From > http://www.cmake.org/cmake/help/cmake2.6docs.html#command:add_custom_target: > > "Adds a target with the given name that executes the given commands. > The target has no output file and is ALWAYS CONSIDERED OUT OF DATE > even if the commands try to create a file with the name of the > target." > > Ok, so is it simply impossible to do delta builds if my build process > needs add_custom_command/add_custom_target invocations? Is there some > better way to have CMake create the headers for me? Does this behavior > of add_custom_target only occur when I add a new target dependent on > ALL? Why do you add "ALL" in your case? Won't generateheader be called when needed when you remove the ALL argument to add_custom_target? Note that another way to go is completely remove the add_custom_target and add the generated header to the concerned add_executable / add_library command. then you have to: set_source_files_properties(results/header.h PROPERTIES GENERATED true) in order to avoid to make add_library/add_executable shout at you about missing files. Then when the concerned libraries and/or executable are built CMake should automatically run your add_custom_command since it advertise it has the missing "results/header.h" as output. -- Erk _______________________________________________ CMake mailing list CMake@cmake.org http://www.cmake.org/mailman/listinfo/cmake
