Qt Moc'ing multiple files in parallel under msbuild - visual-studio-2010

Question

Using the Qt Visual studio plugin it seems to take care of most of almost everything in a seemless manner. Unfortunately it does the moc'ing using a CustomBuild step in msbuild. This results in a serial moc'ing, one after another. Is there a way to convince msbuild to do them in parallel - I'm tired of 7 cores sitting on their laurels like me.
I've seen msbuild's BuildInParallel, but I'm not sure how to make that apply here.
msbuild snippet:
<Project>
...
<ItemGroup>
<CustomBuild Include="a_class4.h">
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">$(QTDIR)\bin\moc.exe;%(FullPath)</AdditionalInputs>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Moc%27ing %(Identity)...</Message>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">.\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp</Outputs>
<Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">"$(QTDIR)\bin\moc.exe" "%(FullPath)" -o ".\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp" -DUNICODE -DWIN32 -DQT_LARGEFILE_SUPPORT -DQT_CORE_LIB -DQT_GUI_LIB "-I." "-I.\GeneratedFiles" "-I$(QTDIR)\include" "-I.\GeneratedFiles\$(ConfigurationName)\." "-I$(QTDIR)\include\qtmain" "-I$(QTDIR)\include\QtCore" "-I$(QTDIR)\include\QtGui" "-I." "-I." "-I." "-I."</Command>
</CustomBuild>
<CustomBuild Include="a_class3.h">
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">$(QTDIR)\bin\moc.exe;%(FullPath)</AdditionalInputs>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Moc%27ing %(Identity)...</Message>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">.\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp</Outputs>
<Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">"$(QTDIR)\bin\moc.exe" "%(FullPath)" -o ".\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp" -DUNICODE -DWIN32 -DQT_LARGEFILE_SUPPORT -DQT_CORE_LIB -DQT_GUI_LIB "-I." "-I.\GeneratedFiles" "-I$(QTDIR)\include" "-I.\GeneratedFiles\$(ConfigurationName)\." "-I$(QTDIR)\include\qtmain" "-I$(QTDIR)\include\QtCore" "-I$(QTDIR)\include\QtGui" "-I." "-I." "-I." "-I."</Command>
</CustomBuild>
</ItemGroup>
...
</Project>

Answer 1

You can build in parallel using jom:
http://labs.qt.nokia.com/2009/03/27/speeding-up-visual-c-qt-builds/

Answer 2

I am not very familiar with Visual Studio projects ... so don't know if the "CustomBuild" ItemGroup name and its metadata names bear significance. If they do, you might need to
Modify the ItemGroup name to something else
Identify the msbuild targets file which handles that and fix it for parallel processing
Here is a standalone msbuild file that can execute things in parallel.
Notes:
The ping -n 30 -w 1000 127.0.0.2>nul command has been added so that I could launch process explorer and find enough time to count how many instances of ping.exe were spawned.
I was trying to ping 127.0.0.2 because I wanted ping not to finish earlier.
There is nothing practically useful happening in the file ... only echoing properties as a proof of concept.
<Project xmlns="http://schemas.microsoft.com/developer/msbuild/2003" DefaultTargets="RunMe">
<ItemGroup>
<CustomBuild Include="a_class4.h">
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">$(QTDIR)\bin\moc.exe;%(FullPath)</AdditionalInputs>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Moc%27ing %(Identity)...</Message>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">.\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp</Outputs>
<Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">"$(QTDIR)\bin\moc.exe" "%(FullPath)" -o ".\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp" -DUNICODE -DWIN32 -DQT_LARGEFILE_SUPPORT -DQT_CORE_LIB -DQT_GUI_LIB "-I." "-I.\GeneratedFiles" "-I$(QTDIR)\include" "-I.\GeneratedFiles\$(ConfigurationName)\." "-I$(QTDIR)\include\qtmain" "-I$(QTDIR)\include\QtCore" "-I$(QTDIR)\include\QtGui" "-I." "-I." "-I." "-I."</Command>
</CustomBuild>
<CustomBuild Include="a_class3.h">
<AdditionalInputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">$(QTDIR)\bin\moc.exe;%(FullPath)</AdditionalInputs>
<Message Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">Moc%27ing %(Identity)...</Message>
<Outputs Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">.\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp</Outputs>
<Command Condition="'$(Configuration)|$(Platform)'=='Debug|Win32'">"$(QTDIR)\bin\moc.exe" "%(FullPath)" -o ".\GeneratedFiles\$(ConfigurationName)\moc_%(Filename).cpp" -DUNICODE -DWIN32 -DQT_LARGEFILE_SUPPORT -DQT_CORE_LIB -DQT_GUI_LIB "-I." "-I.\GeneratedFiles" "-I$(QTDIR)\include" "-I.\GeneratedFiles\$(ConfigurationName)\." "-I$(QTDIR)\include\qtmain" "-I$(QTDIR)\include\QtCore" "-I$(QTDIR)\include\QtGui" "-I." "-I." "-I." "-I."</Command>
</CustomBuild>
</ItemGroup>
<Target Name="RunMe">
<Message Text="First populate an ItemGroup such that we can use it for parallel processing"/>
<ItemGroup>
<InputForParallelInvoke Include="$(MSBuildThisFileFullPath)">
<Properties>InputFile=%(CustomBuild.Identity);
AdditionalInputs=%(CustomBuild.AdditionalInputs);
Message=%(CustomBuild.Message);
Outputs=%(CustomBuild.Outputs);
Command=%(CustomBuild.Command)</Properties>
</InputForParallelInvoke>
</ItemGroup>
<MSBuild Projects="#(InputForParallelInvoke)" Targets="InvokeInParallel" BuildInParallel="True" />
</Target>
<Target Name="InvokeInParallel">
<Exec Command="ping -n 30 -w 1000 127.0.0.2>nul & echo Properties=$(InputFile) ##### $(AdditionalInputs) ##### $(Message) ##### $(Outputs) ##### $(Command)"/>
</Target>
</Project>
When I invoke it on via msbuild thus msbuild /m \path\to\file /p:Configuration=Debug;Platform=Win32 I see 2 instances of ping.exe.
Hope this helps solve your problem.