Using Ubuntu Debug Packages in GDB (2)

From last blog, I’ve demostrated the usage of Ubuntu *-dbg packages. However, not all *-dbg packages seem to work as libssl0.9.8-dbg. For instance, libcurl3-dbg and libqt4-dbg packages do not work. I’m afraid some debug info are missing in these two packages. I’m not sure.

I googled a lot, but was not able to find a solution. So I decided to build the debug version of the two library myself. Here are steps for libcurl:

After all, the compiled binary is located in /home/gonwan/testgdb/curl-7.19.7/lib/.libs/. Note, this is a hidden folder.

Here comes our test code:

Build commands:

I use /usr/lib/libcurl.so.4 instead of lcurl, since lcurl will link the binary to /usr/lib/libcurl-gnutls.so.4. But I currently cannot afford it :(. Last, start our GDB:

It prints the backtrace now, though I’m not so accustomed to console debugging. I add the LD_LIBRARY_PATH environment to let our test program find our homemade version of libcurl.so.4. In fact, we can run ldd like following lines. You see the re-direction?

Later, I successfully made it possible to debug Qt source code in IDE. I chose QtCreator, since it has both windows and linux version, and it’s easy to install and configure. I also built my homemade version of Qt:

I only built the most common modules, excluding webkit, script, xmlpatterns, phonon, multimedia and declarative modules. It took only 25 minutes to finish (An entire build under windows may take 3 – 4 hours.). After all, start your QtCreator, create a Qt console project with the source below:

Build the project in debug mode. And now, here’s the magic: Go to Project tab –> Run Settings –> Run Environment, append our homemade Qt library path to LD_LIBRARY_PATH. In my example, it’s /home/gonwan/testgdb/qt4-x11-4.6.2/lib. Ok, you’re almost done! Go back to the Edit tab, set a breakpoint at line 4 (or line 3 as you like), press F5 to start debugging the project. Then continue pressing F11, you will find GDB has stepped into Qt source code! Let me take a screenshot:

qtcreator_qt4debug

In order to load our homemade *.so, we can also run “make install”.

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