~~Title: Enlightenment debugging~~ ==== Enlightenment Debugging ==== This tutorial aims at providing a comprehensive and reproducible documentation to debug Enlightenment. It is divided in two sections: * [[#Debugging_Enlightenment_using_GDB|GDB]] * [[#Valgrind|Valgrind]] Before debugging make sure your debug symbols are enabled, if not, go to the [[/docs/distros/#Enable_debug_symbols_Optional|Enable debug symbols]] section. === Debugging Enlightenment using GDB === In order to use GDB, we will simulate a crash in Enlightenment. Start by running Enlightenment on a machine. Then switch to another tty (CTRL+ALT+F1 for tty1). At that point, 2 processes are interesting, ''enlightenment'' and ''enlightenment_start''. Indeed, ''enlightenment'' is traced by ''enlightenment_start''. Then setup SEGV to segfault enlightenment. kill -SIGSEGV $(pidof enlightenment) ''enlightenment_start'' will open a pop-up named Enlightenment Error. This pop-up indicates that Enlightenment segfaulted and allows to recover or log out but also detaches from the child process (Enlightenment) and let advanced users use GDB to debug it. #gdb on the running enlightenment process gdb enlightenment $(pidof enlightenment) After a bit a prompt is available, if you want, you can save the traces in a log: #save the traces in log.txt set logging file log.txt set logging on == Backtrace == Use the backtrace command to get information about frames to know where the segfault is coming from. (gdb) bt #0 0xb7d539f8 in select () from /lib/tls/libc.so.6 #1 0xb7dff66a in _XEnq () from /usr/X11R6/lib/libX11.so.6 #2 0xb7dffa7e in _XRead () from /usr/X11R6/lib/libX11.so.6 #3 0xb7e01795 in _XReadEvents () from /usr/X11R6/lib/libX11.so.6 #4 0xb7defa88 in XNextEvent () from /usr/X11R6/lib/libX11.so.6 #5 0x0809b698 in e_alert_show ( text=0x80a34f0 "This is very bad. Enlightenment has segfaulted.\nThis is not meant to happen and is likely a sign of a\nbug in Enlightenment or the libraries it relies on.\n\nYou can gdb attach to this process now to try"...) at e_alert.c:136 #6 0x0808f706 in e_sigseg_act (x=11, info=0x80a9fb0, data=0x80aa030) at e_signals.c:54 #7 #8 0xb7d539f8 in select () from /lib/tls/libc.so.6 #9 0xb7f814ee in _ecore_main_select (timeout=0) at ecore_main.c:338 #10 0xb7f819ba in _ecore_main_loop_iterate_internal (once_only=0) at ecore_main.c:575 #11 xb7f81a2b in ecore_main_loop_begin () at ecore_main.c:79 #12 0x08059bb3 in main (argc=1, argv=0xbffff144) at e_main.c:551 As you can see in the stack trace, GDB finds the segfault in libc and pops to the main function in e_main. But it doesn't seem credible to have a bug in libc or x, the important thing is Enlightenment has its own segfault handler which is very explicit on frame 5. The e_sigseg_act() function at frame 6 is called directly from the kernel when the program segfaults, meaning enlightenment causes the segfault. So, the segfault comes from the select function (a libc function) at frame 8 called in _e_core_main_select_function at frame 9. == Go in a frame == So, the reason of segfault seems to be at frame 9, when ''select'' function is called. Let's go to frame 9: fr 9 #9 0xb7f814ee in _ecore_main_select (timeout=0) at ecore_main.c:338 338 ret = select(max_fd + 1, &rfds, &wfds, &exfds, t); (gdb) l 333 } 334 } 335 #ifndef WIN32 336 if (_ecore_signal_count_get()) return -1; 337 #endif 338 ret = select(max_fd + 1, &rfds, &wfds, &exfds, t); 339 if (ret < 0) 340 { 341 if (errno == EINTR) return -1; 342 } The first command **//fr 9//** gives useful information: name of the file, number of the line, the function called, ... The second command **//l//** lists the code around the called function. Another useful command allows to print the variables, the parameters, helping you to find out the problem, a wrong parameter, a null pointer... (gdb) p ret $1 = -4 (gdb) p rfds $2 = {__fds_bits = {1280, 0 }} (gdb) p wfds $3 = {__fds_bits = {0 }} (gdb) p exfds $4 = {__fds_bits = {0 }} GDB is important to start debugging, it will help you to resize the problem even if sometimes is not enough. ---- === Valgrind === Valgrind aims at finding memory problems but for that Enlightenment needs to be run through Valgrind. == Prerequisites == This tutorial will present 3 different ways to run enlightenment through Valgrind: * Remote debugging * Xephyr invocation * Xinit invocation The easiest way is certainly Xephyr because it allows to target a window on a X server host, sadly Xephyr doesn't yet support OpenGL and any issue that may be related to it will need to use the Xinit version. == Remote Debugging == Enlightenment_start launcher will handle setting up environment variables, paths, and launching any other required services before Enlightenment starts. Fortunately, there are some options in enlightenment_start that allow to run Enlightenment through Valgrind: $enlightenment_start --help Options: -valgrind[=MODE] Run enlightenment from inside valgrind, mode is OR of: 1 = plain valgrind to catch crashes (default) 2 = trace children (thumbnailer, efm slaves, ...) 4 = check leak 8 = show reachable after processes finish. all = all of above -massif Run enlightenment from inside massif valgrind tool. -callgrind Run enlightenment from inside callgrind valgrind tool. -valgrind-log-file= Save valgrind log to file, see valgrind's --log-f First of all, get the IP address of your host machine and connect to it, then on the distant machine, launch X: #launch X on tty1 sudo X -ac :1 & For example, if you want to check leak and save traces in a log file: export DISPLAY=:1 enlightenment_start -valgrind=4 -valgrind-log-file=log.txt At that point, Enlightenment should have started on your host machine. If the session is closed then the summary of Valgrind should look like: ==1488== ==1488== HEAP SUMMARY: ==1488== in use at exit: 4,479,487 bytes in 24,302 blocks ==1488== total heap usage: 336,239 allocs, 311,937 frees, 88,068,674 bytes allocated ==1488== ==1488== LEAK SUMMARY: ==1488== definitely lost: 825 bytes in 15 blocks ==1488== indirectly lost: 39 bytes in 2 blocks ==1488== possibly lost: 384 bytes in 1 blocks ==1488== still reachable: 4,478,239 bytes in 24,284 blocks ==1488== suppressed: 0 bytes in 0 blocks ==1488== Rerun with --leak-check=full to see details of leaked memory ==1488== ==1488== For counts of detected and suppressed errors, rerun with: -v ==1488== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0) == Valgrind Invocation - Xinit == Create a file called .xinitrc-debug in your home with the following content: #!/bin/sh ulimit -c unlimited log_file="$HOME/enlightenment-xinit-debug-valgrind.log" #path of you installation enlightenment_install_path=/usr/local #set vars LD_LIBRARY_PATH="$enlightenment_install_path/lib" PATH="$enlightenment_install_path/bin:$PATH" #log to file echo "using installation at $enlightenment_install_path" echo "LD_LIBRARY_PATH=$LD_LIBRARY_PATH" > $log_file echo "PATH=$enlightenment_install_path/bin: ... " >> $log_file #start e with valgrind $enlightenment_install_path/bin/enlightenment_start -valgrind 2>&1 | tee -a "$log_file" You can now start a debugging session, after X was closed if it is not the case log out: /usr/bin/xinit ~/.xinitrc-debug -- :1 -nolisten tcp == Valgrind Invocation - Xephyr == Xephyr is a display server implementing the X11 display server protocol which targets a window on a X Server host. So, for this it is important that X is launched, you can even do it in your usual window manager under X. Of course, you need to install Xephyr. Xephyr -ac -br -noreset -screen 800x600 :1 *ac: disable access control restrictions *br: create root window with black background *noreset: don't reset after last client exists *screen 800x600: Specify screen characteristics A black screen should now be displayed, and the interesting thing for us is that you can launch a window manager on it with Valgrind in addition: DISPLAY=:1 enlightenment_start -valgrind