Development/Tutorials/Debugging/Debugging symbols

Debugging symbols allow you to debug your application better. Debugging symbols are added to your binary by the compiler. You have to decide during the cmake step if you want debugging symbols or not. To compile your application with debugging symbols, use

cmake . -DCMAKE_BUILD_TYPE=debugfull

to compile it without debugging symbols, use

cmake . -DCMAKE_BUILD_TYPE=release

Depending on your decision, output generated with the command kDebug will also be (debugfull) or not be (release) added to your application.

As an example, let's write an application that crashes:

main.cpp

    
#include <KApplication>
#include <KAboutData>
#include <KCmdLineArgs>
#include <KMessageBox>
#include <iostream>
 
using namespace std;

int main (int argc, char *argv[])
{
    KAboutData aboutData( "tutorial1", 0, ki18n("Tutorial 1"), "1.0",
                          ki18n("Displays a KMessageBox popup"),
                          KAboutData::License_GPL,
                          ki18n("(c) 2009"), ki18n("Some text..."),
                          "http://tutorial.com/",
                          "[email protected]");
 
    KCmdLineArgs::init( argc, argv, &aboutData );
    KApplication app;

    KMessageBox::questionYesNo( 0, i18n( "Hello World" ) );
    int* i;
    cout << "i is at " << i << " value " << *i << endl;
    i=(int*)0x400890;
    cout << "i is at " << i << " value " << *i << endl;
    // We now try to read from memory address 0x400891
    i=(int*)0x400891;
    cout << "i is at " << i << " value " << *i << endl;

    return 0;
}

CMakeLists.txt

project (tutorial1)
find_package(KDE4 REQUIRED)
include (KDE4Defaults)
include_directories(${KDE4_INCLUDES})
set(tutorial1_SRCS main.cpp)
kde4_add_executable(tutorial1 ${tutorial1_SRCS})
target_link_libraries(tutorial1 ${KDE4_KDEUI_LIBS})
install(TARGETS tutorial1  ${INSTALL_TARGETS_DEFAULT_ARGS})

Now let's compile this without debugging symbols:

cmake . -DCMAKE_BUILD_TYPE=release && make -j4

We see that the resulting file is small:

# ll tutorial1
-rwxr-xr-x 1 root root 18133 Jul 11 18:07 tutorial1

With debugging symbols, the file is bigger:

cmake . -DCMAKE_BUILD_TYPE=debugfull && make
# ll tutorial1
-rwxr-xr-x 1 root root 260256 Jul 11 18:09 tutorial1