Browsing and debugging code with Qt Creator:

Download and installation

The current version can be downloaded from:

http://qt.nokia.com/downloads

Scroll down to the bottom of the page and look at the left. There you find binaries for different platforms. The part of Qt needed by Qt Creator is included in the binary. The current version runs fine under SLC5, under SLC4 there may be problems. Download the correct version, make it executable (chmod +r) and run the program, a dialog will come up (so you need to run an X11 session, either via a direct connection or via VNC) asking whether you agree with the license and where you want to store the program. To run the program: it has the name qtcreator and is stored in the bin directory of the directory in which everything is stored. Once the program is running: under the "Help" button at the left you will find a manual for the program.

Browsing code

With Qt Creator up and running a new project file (.pro) file can be produced. One can start with an empty file and add source files to it if needed while studying code one is interested in. This is an example of a .pro file used for browsing relevant code for the ReadoutApplication:
INCLUDEPATH += tdaq/installed/include \
    tdaq-common/installed/include \
    dqm-common/installed/include \
    boost \
    tdaq/installed/i686-slc4-gcc34-opt/include
SOURCES += tdaq/ROSApplication/src/ROSApplication.cpp \
    tdaq/ROSCore/src/IOManager.cpp \
    tdaq/ROSIO/src/DcTriggerIn.cpp \
    tdaq/ROSModules/src/RobinReadoutModule.cpp \
    tdaq/msg/src/Port.cxx \
    tdaq/ROSIO/src/ReleaseRequest.cpp \
    tdaq/ROSIO/src/GarbageCollectionRequest.cpp \
    tdaq/ROSModules/src/RobinDataChannel.cpp \
    tdaq/ROSCore/src/FragmentRequest.cpp \
    tdaq/ROSCore/src/RequestHandler.cpp \
    tdaq/ROSCore/src/Request.cpp \
    tdaq/ROSIO/src/ROSFragmentBuilder.cpp \
    tdaq/ROSEventFragment/src/FullFragment.cpp \
    tdaq/ROSEventFragment/src/ROBFragment.cpp \
    tdaq/ROSBufferManagement/src/Buffer.cpp \
    tdaq/ROSMemoryPool/src/MemoryPool_malloc.cpp \
    tdaq/ROSMemoryPool/src/MemoryPool_CMEM.cpp \
    tdaq/ROSMemoryPool/src/MemoryPool.cpp \
    tdaq/ROSRobin/src/lib/Rol.cpp \
    tdaq/ROSRobin/src/lib/Robin.cpp \
    tdaq/ROSMemoryPool/src/WrapperMemoryPool.cpp \
    tdaq/ROSIO/src/DcDataOut.cpp \
    tdaq/ROSModules/src/EthSequentialReadoutModule.cpp \
    tdaq/ROSModules/src/EthSequentialDataChannel.cpp \
    tdaq/ROSCore/src/SequentialDataChannel.cpp \
    tdaq/ROSIO/src/DataDrivenTriggerIn.cpp \
    tdaq/ROSIO/src/RODFragmentBuilder.cpp \
    tdaq/ROSIO/src/EmulatedTriggerIn.cpp \
    tdaq/ROSIO/src/DataDrivenTriggerIn.cpp
So one sees that the contents of the file is simple: it is a specification of the include paths and of the sources. There is one trick and that is that tdaq is a symbolic link to the tdaq software installation (in the same directory as the .pro file).  tdaq-common, dqm-common, and boost are also symbolic links to the tdaq-common, dqm-common and Boost installations (for Boost the link points to the directory with the includes for Boost). For afs the links are as follows:
boost -> /afs/cern.ch/atlas/project/tdaq/inst/sw/lcg/external/Boost/1.39.0_python2.5/slc4_ia32_gcc34/include/boost-1_39/boost
dqm-common -> /afs/cern.ch/atlas/project/tdaq/inst/dqm-common/dqm-common-00-10-00<>
tdaq -> /afs/cern.ch/atlas/project/tdaq/inst/tdaq/tdaq-02-00-03/
tdaq-common -> /afs/cern.ch/atlas/project/tdaq/inst/tdaq-common/tdaq-common-01-14-00
Once the .pro file and the links are in place the .pro file can be opened by Qt Creator (first press the "Edit" button at the left). Without compilation all include files are known to the IDE,  definitions are found by right clicking on the item of which the definition has to be found. For opening a source file, double click it in the list of files at the left. For finding a method in the file clicking <Select Symbol> at the right of the file name at the top of the windowand results in a list of methods. The cursor will jump to the one that is selected from the list.

An example .pro file and the links for afs can be found in:
/afs/cern.ch/user/v/vermeule/public/ReadoutApplication
One may have to experiment somewhat for getting familiar with how to useQt Creator. One thing that may not be obvious is how one adds a source file to the .pro file: click right on the name of the project and then select "Add Existing files". The appearance of text files can be improved by choosing another font: select from the "Tools"  menu the last item: "Options.." and then "Text Editor" at the left side of the dialog box. "LucidaTypewrite", Size 9 is a good choice

Debugging

It is possible to connect to a running application for debugging. Select "Debug" at the left of the window. This results at the bottom of the window in two subwindows. One is used for displaying the call stack (at the left) and the other for variables ot breakpoints or threads. It is possible to set breakpoints in the source code by clicking in the left margin of the source code subwindow. A red dot appears, the breakpoint can again be removed by clicking on the red dot. Connecting gdb to a running application is done by Debug->Start Debugging -> Attach to Running External Application. This results in a list of processes, from which the process can be selected associated with the .pro file. Once the process hits a breakpoint it will stop execution, variables can be inspected and one can continue with stepping through the code. If the process crashes before hitting a breakpoint a post-mortem analysis of the call stack and of values of variables is possible. It may occur that the process stops execution after attaching to it, click the green arrow at the top left of the left debugger subwindow if execution should continue.

Tip

The source window can be split in subwindows, in which the content of different source files can be displayed, by means of "Split" or "Split Side by Side" in the "Window" menu.