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| This page describes how you can debug a KIO ioslave.
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| ==How to Get Debug Output==
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| === GUI (Qt5/KF5 instructions) ===
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| # Launch the <code>kdebugsettings</code> tool, either from terminal or from KRunner (the latter can be invoked with Alt + F2)
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| # Type the name of the KIO Slave (e.g. ftp, http, ...). (If it's not listed, it doesn't use categorized debug output, so either its output is always on, or commented out in the code, in which case it needs to be ported to qCDebug)
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| # From the drop-down menu next to each KIO Slave you're interested in, select '''Full Debug'''
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| # Press '''OK''' to close the dialog and the save your changes
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| # You can either run <code>kdeinit5</code> in terminal, in which case the output from any IO slave that's started afterwards will show up in that terminal OR
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| # Alternatively log out then log back in, and additional debug info will typically end up in ~/.X.err, ~/.xsession-errors or ~/.local/share/sddm/xorg-session.log
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|
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| Notes:
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| * If you have rebuilt an IO Slave from source with some changes you'll need ensure that <code>kdeinit5</code> will pick it up; this works with KIO from the KDE repos:
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| {{Input|1=<nowiki>
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| cd <path to build dir>/bin
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| export LD_LIBRARY_PATH=$PWD
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| export QT_PLUGIN_PATH=$PWD
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| kdeinit5</nowiki>}}
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| ** in the first <code>cd</code> command you change to the directory containing the compiled binaries, in KIO case it's ''<build dir>/bin''.
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|
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| * Instead of using <code>kdebugsettings</code>, you can change the Qt logging categories rules temporarily, in terminal:
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| {{Input|1=<nowiki>
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| export QT_LOGGING_RULES="*kio*=true"
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| </nowiki>}}
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| ** for more information see [https://doc.qt.io/qt-5/qloggingcategory.html this].
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| === GUI (Qt4/kdelibs4 instructions) ===
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|
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| # Press ALT+F2.
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| # Enter 'kdebugdialog --fullmode' without the quotes and press enter.
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| # Select the desired number in the "Debug area", e.g. 7103 for http.
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| # In the [Information] box, select "File" as the output.
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| # Enter the desired file name, e.g. /tmp/kio_http.log.
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| # Press OK to close the dialog.
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| # Press ALT+F2, type ''kdeinit4'' and press enter or alternatively log out of KDE and log back in.
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| This will print additional debug info to the stderr of your kdeinit process, which typically ends up in ~/.X.err, ~/.xsession-errors or ~/.local/share/sddm/xorg-session.log
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|
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| ===Manual (Qt4/kdelibs4 instructions)===
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| It is useful to redirect the debug output of your particular slave to a file
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| instead of stderr. E.g. I myself use the following lines in
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| $KDEDIR/share/config/kdebugrc.
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| <pre>
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| [7113]
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| InfoOutput=0
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| InfoFilename=/tmp/http
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| [7103]
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| InfoOutput=0
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| InfoFilename=/tmp/http
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| </pre>
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| This redirects all debug info for areas 7103 and 7113 (as used by kio_http)
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| to the file /tmp/http.
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|
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| To get debug information from the SMB slave you can add the following to
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| kioslaverc:
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| <pre>
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| [SMB]
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| DebugLevel=100
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| </pre>
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| This will print additional debug info to the stderr of your kdeinit process,
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| which typically ends up in ~/.X.err, ~/.xsession-errors or ~/.local/share/sddm/xorg-session.log
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|
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| ==How does an io-slave get started?==
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| Your application requests 'klauncher' via DBus for a slave. If 'klauncher' does not have an idle slave ready, it will ask kdeinit to start a new one. kdeinit forks and dlopens the library that contains the io-slave.
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| Then it calls a function called kdemain() in the library.
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|
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| ==Attaching gdb to an io-slave==
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| ===If KDE_FORK_SLAVES is not set===
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| If <code>KDE_FORK_SLAVES</code> environment variable is ''not set'', your application asks <code>klauncher</code> via DBus for an io-slave. If <code>klauncher</code> does not have an idle io-slave ready, it will ask <code>kdeinit</code> to start a new one. <code>kdeinit</code> forks and dlopens the library that contains the requested io-slave.
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| Then it calls a function called <code>kdemain()</code> in the library.
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|
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| Due to the above sequence it is rather hard to get an io-slave in your debugger. But wait there is hope! You can start </code>klauncher</code> in such a way that io-slaves for a certain protocol (the first parameter of KIO::SlaveBase() constructor of the Slave class) are started in debug mode.
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|
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| E.g. to start all 'http' slaves in debug mode, you type:
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| <pre>
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| KDE_SLAVE_DEBUG_WAIT=http kdeinit5
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| </pre>
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|
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| This will restart 'kdeinit' and 'klauncher'.
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|
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| Note:
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| The string after the equal signal designates the name of a service, not the name of the slave! E.g. if you want to debug the kio_imap4, you must use:
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| <pre>
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| KDE_SLAVE_DEBUG_WAIT=imap kdeinit5
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| </pre>
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|
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| For example, these commands won't work:
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| <pre>
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| KDE_SLAVE_DEBUG_WAIT=imap4 kdeinit5
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| KDE_SLAVE_DEBUG_WAIT=143 kdeinit5
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| </pre>
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|
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| When your application now requests an http io-slave, the io-slave will be started kdeinit, but before it calls kdemain() (cq. main()) it will suspend the slave by sending it a SIGSTOP signal.
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|
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| In the terminal from which you started kdeinit you will get a message like this:
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| <pre>
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| kdeinit: Suspending process
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| kdeinit: 'gdb kdeinit 16779' to debug
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| kdeinit: 'kill -SIGCONT 16779' to continue
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| </pre>
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|
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| You can now debug your slave by using <code>gdb kdeinit 16779</code> in a terminal.
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|
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| Note that modern Linux Kernels disable ptrace. If gdb says "ptrace: Operation not permitted." then you need to use a command like this:
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| <pre>
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| echo 0 | sudo tee /proc/sys/kernel/yama/ptrace_scope
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| </pre>
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|
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| If you don't want to debug a slave you can let it continue by sending it a SIGCONT, with e.g. <code>kill -SIGCONT 16779</code>. Be aware that slaves will not be killed while they are suspended.
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|
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| Once you have started gdb, you can set e.g. breakpoints and then resume the slave by typing <code>continue</code> (or <code>c</code> for short). The debugger will return immediate with a message that a "SIGSTOP has been received" so you will have to type <code>continue</code> a second time.
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|
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| See also [[Development/Tutorials/Debugging/Debugging_on_MS_Windows#Debugging_kioslaves|Windows-specific notes on debugging io-slaves]].
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| ===If KDE_FORK_SLAVES is set=== | | ===If KDE_FORK_SLAVES is set=== |
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| Read the previous section, because a lot of what it said applies here too, the only difference is how the io-slave is started.
| | The only difference between this section and the previous one is how the io-slave is started. |
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| If you set the <code>KDE_FORK_SLAVES</code> environment variable: | | If the io-slaves are forked (this became the default since Frameworks 5.86, before that you needed to set the <code>KDE_FORK_SLAVES</code> environment variable, e.g. <code>export KDE_FORK_SLAVES=1</code> and start the application from that terminal). |
| {{Input|1=<nowiki>
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| export KDE_FORK_SLAVES=1 | |
| </nowiki>}} | |
| then start your application from that terminal, a dedicated io-slave will be created for your application in-process. In this case to attach gdb to the io-slave, first find the pid of the io-slave process, you can do that by examining the output of e.g.:
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| <pre>
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| ps -ef | grep kdeinit
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| </pre>
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|
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| let's say you're trying to debug the Trash io-slave, the output should contain something like:
| | Now when you start your application, a dedicated io-slave will be created in-process by the <code>kioslave</code> executable. To make the io-slave start then wait for debug, just like with the kdeinit/klauncher approach, you need to export <code>KDE_SLAVE_DEBUG_WAIT</code>, for example: |
| <pre> | |
| username 29333 29156 0 17:57 ? 00:00:00 trash.so [kdeinit5] trash local:/run/user/1000/klauncherJvaxHq.1.slave-socket local:/run/user/1000/<app-name>nUqbkc.4.slave-socket
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| </pre> | |
| or you could simply use:
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| <pre> | | <pre> |
| ps -ef | grep trash.so
| | // Will start any io-slave then call `kill -SIGSTOP pid` to make it wait for debugging, |
| </pre>
| | // e.g. you can create a breakpoint ...etc |
| the pid is 29333 in this case. Note that you may need to examing the output before starting your application and after starting it, in case there are other io-slaves already running.
| | export KDE_SLAVE_DEBUG_WAIT=all |
| | kioslave5: Suspending process to debug io slave(s): all |
| | kioslave5: 'gdb kioslave5 28008' to debug |
| | kioslave5: 'kill -SIGCONT 28008' to continue |
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| To attch gdb to that io-slave process:
| | // This will do the same but only for kio_file |
| <pre>
| | export KDE_SLAVE_DEBUG_WAIT=file |
| gdb --pid 29333
| | kioslave5: Suspending process to debug io slave(s): file |
| </pre>
| | kioslave5: 'gdb kioslave5 25208' to debug |
| (if there is only one trash.so process running you can use <code>gdb --pid $(pidof trash.so)</code>
| | kioslave5: 'kill -SIGCONT 25208' to continue |
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| and then follow the same debugging steps from the previous section.
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| ==Debugging io-slaves with valgrind== | |
| KLauncher can be told to run certain io-slaves through valgrind. The following
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| command can be used to let klauncher run all https io-slaves via valgrind:
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| <pre>
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| KDE_SLAVE_VALGRIND=https kdeinit5
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| </pre>
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| The valgrind output will appear as the stderr output of the kdeinit process.
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| The $VALGRIND_OPTS environment variable can be used to pass options to valgrind.
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| If you want to use a different skin:
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| <pre>
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| KDE_SLAVE_VALGRIND_SKIN=callgrind ( for example )
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| </pre> | | </pre> |
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| == specific kioslaves ==
| | then follow the same debugging steps from the previous section. |
| * [[Guidelines_and_HOWTOs/Debugging/Debugging IOSlaves/Debugging kio_fish|kio_fish]]
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| * [[Guidelines_and_HOWTOs/Debugging/Debugging IOSlaves/Debugging kio_sftp|kio_sftp]]
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| * [[Guidelines_and_HOWTOs/Debugging/Debugging IOSlaves/Debugging kio_smb|kio_smb]]
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If KDE_FORK_SLAVES is set
The only difference between this section and the previous one is how the io-slave is started.
If the io-slaves are forked (this became the default since Frameworks 5.86, before that you needed to set the KDE_FORK_SLAVES environment variable, e.g. export KDE_FORK_SLAVES=1 and start the application from that terminal).
Now when you start your application, a dedicated io-slave will be created in-process by the kioslave executable. To make the io-slave start then wait for debug, just like with the kdeinit/klauncher approach, you need to export KDE_SLAVE_DEBUG_WAIT, for example:
// Will start any io-slave then call `kill -SIGSTOP pid` to make it wait for debugging,
// e.g. you can create a breakpoint ...etc
export KDE_SLAVE_DEBUG_WAIT=all
kioslave5: Suspending process to debug io slave(s): all
kioslave5: 'gdb kioslave5 28008' to debug
kioslave5: 'kill -SIGCONT 28008' to continue
// This will do the same but only for kio_file
export KDE_SLAVE_DEBUG_WAIT=file
kioslave5: Suspending process to debug io slave(s): file
kioslave5: 'gdb kioslave5 25208' to debug
kioslave5: 'kill -SIGCONT 25208' to continue
then follow the same debugging steps from the previous section.
