On Mar 7, 2012, at 11:43 AM, Andreas Pakulat wrote:
> On 07.03.12 10:10:27, Michael Jackson wrote:
>> In an effort to speed up the build of a project that uses Qt (and moc) I
>> tried an alternate approach with the moc files. Normally I use the basic
>> idea of gathering the headers that need to be "moc'ed" and feed those to moc
>> with this type of CMake Code:
>>
>> QT4_WRAP_CPP( FilterWidgets_Generated_MOC_SRCS ${QFilterWidget_HDRS}
>> ${FilterWidget_GEN_HDRS})
>>
>> The in the Add_Executable(...) call include the
>> ${FilterWidgets_Generated_MOC_SRCS} variable to the list of sources. In my
>> project I have at least 30 auto-generated files which all get moc'ed. That
>> gives me an additional 60 compiled files. So I tried the idea of #include
>> "moc_[some_file.cxx]" in each of the auto-generated .cpp files for each
>> Widget. This would cut the number of files compiled in half. The issue is
>> that since they are being #include'ed in the .cpp files then they do NOT
>> need to be compiled themselves so I took the
>> ${FilterWidgets_Generated_MOC_SRCS} out of the list of sources in the
>> add_executable() call. What happened is that CMake did NOT run moc on those
>> headers because there were now NOT included in the build.
>>
>> So for that version of the cmake code I have something like this:
>>
>> QT4_WRAP_CPP( FilterWidgets_Generated_MOC_SRCS ${FilterWidget_GEN_HDRS})
>> QT4_WRAP_CPP( FilterWidgets_MOC_SRCS ${QFilterWidget_HDRS} )
>>
>> Is there a way to forcibly run the moc step even if the resulting source
>> files are NOT directly included in the add_executable? Custom_Command?
>> Add_Depends?
>
> A few options I can think of:
>
> - Use the automoc developed as part of KDE (its pure-Qt though)
> https://projects.kde.org/projects/kdesupport/automoc/repository
> - Use the automoc function from FindQt4.cmake
> - Use the new automoc function in CMake 2.8.7
>
> All of these will help handle the qt4_wrap_cpp stuff for you as long as
> you have the #include. Note that I think there's at least 2 or 3
> differnet filenames for the include depending on which of the above you
> use (foo.moc vs moc_foo.cpp vs. moc_foo.cxx or something like that).
>
> If none of them is an option for you then I guess using
> add_custom_target and add_dependencies is the way to go.
>
> Andreas
>
I looked into the automoc functionality and after some tinkering around I think
there is still a disconnect in my cmake code. When are the source/header files
scanned by automoc to determine if they will have moc run on them.
Currently during cmake time I generate a blank header and source file (well,
there is a #error ... in them) which then get over written by a new files
during build time. The new files are complete and proper C++ source
files/headers with the Q_OBJECT macro in the header and #include "moc_*.cpp" in
the source file. When I compile (using makefiles on OS X currently as a test) I
get an error that the moc_*.cpp file can not be found and searching the entire
build directory does not reveal the file. If I run CMake again and compile then
the auto moc files do appear. From this I think that automoc runs during CMake
time. Is this correct?
--
Mike J.
--
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