Precompiled header support in MOC

loladiro

AFAIK, this is already implemented using:
@
-f[<file>] force #include, optional file name\n"
@

EDIT: never mind, looks like that remove the normal include files.

loladiro

I've had a look at it and it's actually really easy to implement. I can open a merge request with the changes (won't get to it until Sunday though).

ZapB

I've not looked in detail but does it not work if you just use the PRECOMPILED_HEADER variable in your .pro file as described "here":http://doc.qt.nokia.com/4.7-snapshot/qmake-precompiledheaders.html?

jds21

Thanks for the replies. I created a bug report under the category "suggestion" : https://bugreports.qt.nokia.com/browse/QTBUG-20785 .

I have found the /FI compile option for the c compiler which I think I can use instead. ( http://msdn.microsoft.com/en-us/library/8c5ztk84(v=VS.100).aspx ).

I have been using cmake rather than qmake so far, so the PRECOMPILED_HEADER variable was not an option.

steno

If using vs2010, the pre compiled headers switch is pretty much obsolete imo. I find the /MP much more usefull in compiling huge projects, which is incompatible with the /Yu switch.

loladiro

I have created a "merge request":https://qt.gitorious.org/qt/qtbase/merge_requests/41 for this feature

jds21

steno : To me the pch is not obsolete. I think it depends greatly on the project type, and it is important to benchmark. I use /MP and /Yu together - I think it is only the pch generation (/Yc) that is not compatible with /MP. The combination gives faster compile times on my projects than either on its own, the pch giving 50% reduction in time and the MP another 20%.

I prefer not to use /FI as it implicitly adds an include you cannot see in the source code, which can have unexpected consequences.

loladiro : thanks for the merge request.

steno

So what do you do, have another propject create the pre-compiled header and just use it with another project using the /MP switch?

jds21

I use /MP for the whole project, it seems that /Yc overrides it for the one file that generates the pch. I'm actually using a cmake macro, which also sets the dependency of the pch-users on the pch binary. VS may do this automatically if you manually setup the project, I'm not sure.

_nob

I actually hacked the Cmake-Script to include StdAfx.h for me. First test seems to work.

@

PATCHED QT4_WRAP_CPP for use with StdAfx

Original source: Qt4Macros.cmake

MACRO (PCH_QT4_WRAP_CPP outfiles )

get include dirs

QT4_GET_MOC_FLAGS(moc_flags)
QT4_EXTRACT_OPTIONS(moc_files moc_options ${ARGN})

FOREACH (it ${moc_files})
GET_FILENAME_COMPONENT(it ${it} ABSOLUTE)
QT4_MAKE_OUTPUT_FILE(${it} moc_ cxx outfile)
set (moc_flags_append "-fStdAfx.h" "-f${it}") # StdAfx hack.

message (STATUS "Moc Flags append ${moc_flags_append}")

QT4_CREATE_MOC_COMMAND(${it} ${outfile} "${moc_flags};${moc_flags_append}" "${moc_options}")
SET(${outfiles} ${${outfiles}} ${outfile})
ENDFOREACH(it)
ENDMACRO (PCH_QT4_WRAP_CPP)
@

loladiro

Starting with Qt5, the moc will now support the -b<file> option to add optional includes.

joonhwan

great.