GNU gdb (Gentoo 7.11.1 vanilla) 7.11.1
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Reading symbols from /usr/bin/Xorg...done.

warning: core file may not match specified executable file.
[New LWP 21624]
[New LWP 21629]
[New LWP 21628]
[New LWP 21627]

warning: Could not load shared library symbols for linux-vdso.so.1.
Do you need "set solib-search-path" or "set sysroot"?
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".
Core was generated by `/usr/bin/X -nolisten tcp -auth /var/run/sddm/{b40d68c0-714a-4f62-9962-b29e13c81'.
Program terminated with signal SIGABRT, Aborted.
#0  0x00007f9c6c141128 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
54	  return INLINE_SYSCALL (tgkill, 3, pid, selftid, sig);
[Current thread is 1 (Thread 0x7f9c6e5a5900 (LWP 21624))]
#0  0x00007f9c6c141128 in __GI_raise (sig=sig@entry=6) at ../sysdeps/unix/sysv/linux/raise.c:54
#1  0x00007f9c6c14257a in __GI_abort () at abort.c:89
#2  0x00007f9c6c17de11 in __libc_message (do_abort=do_abort@entry=2, fmt=fmt@entry=0x7f9c6c272020 "*** Error in `%s': %s: 0x%s ***\n") at ../sysdeps/posix/libc_fatal.c:175
#3  0x00007f9c6c183926 in malloc_printerr (action=3, str=0x7f9c6c26eea9 "free(): invalid pointer", ptr=<optimized out>, ar_ptr=<optimized out>) at malloc.c:5007
#4  0x00007f9c6c18411e in _int_free (av=0x7f9c6c4a1b00 <main_arena>, p=<optimized out>, have_lock=0) at malloc.c:3868
#5  0x00007f9c67d56a8e in backlight_disable (b=0x21c4170)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/backlight.c:524
#6  0x00007f9c67deb973 in sna_output_backlight_disable (sna_output=0x21c4110)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:887
#7  0x00007f9c67debabb in sna_output_backlight_on (sna_output=0x21c4110)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:943
#8  0x00007f9c67df42fc in sna_output_create_ranged_atom (output=0x21c41e0, atom=0x0, 
    name=0x7f9c67df42fc <sna_output_create_ranged_atom+14> "u\320H\211UȉM\304D\211E\300L\211M\270dH\213\004%(", min=32765, max=1026054688, value=35406096, immutable=0)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:4278
#9  0x00007f9c67dec555 in sna_crtc_force_outputs_off (crtc=0x21c1ca0)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:1283
#10 0x00007f9c67decf6a in overlap (a=0x8302e0 <screenInfo>, b=0x830310 <screenInfo+48>)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:1627
#11 0x00007f9c67df149e in __sna_crtc_set_mode (crtc=0x21c1ca0)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:3064
#12 0x00007f9c67df1b78 in sna_mode_adjust_frame (sna=0x2365e30, x=0, y=37117488)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_display.c:3170
#13 0x00007f9c67e04c63 in sna_save_screen (screen=0x7f9c6c1411b0 <__restore_rt>, mode=32668)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_driver.c:363
#14 0x00007f9c67e04d39 in sna_setup_capabilities (scrn=0x220fa40, fd=1)
    at /usr/src/debug/x11-drivers/xf86-video-intel-2.99.917_p20161024/325570e731b5819e28ce6bae72242914bb2d7f8e/src/sna/sna_driver.c:392
#15 0x0000000000466c4e in dixSaveScreens (client=<optimized out>, on=on@entry=1, mode=mode@entry=0)
    at /usr/src/debug/x11-base/xorg-server-1.18.4/xorg-server-1.18.4/dix/window.c:3149
#16 0x000000000056ee2e in mieqProcessInputEvents () at /usr/src/debug/x11-base/xorg-server-1.18.4/xorg-server-1.18.4/mi/mieq.c:631
#17 0x0000000000475c89 in ProcessInputEvents () at /usr/src/debug/x11-base/xorg-server-1.18.4/xorg-server-1.18.4/hw/xfree86/common/xf86Events.c:168
#18 0x0000000000435d0e in Dispatch () at /usr/src/debug/x11-base/xorg-server-1.18.4/xorg-server-1.18.4/dix/dispatch.c:386
#19 0x0000000000439e23 in dix_main (argc=11, argv=0x7ffd3d286b58, envp=<optimized out>) at /usr/src/debug/x11-base/xorg-server-1.18.4/xorg-server-1.18.4/dix/main.c:300
#20 0x00007f9c6c12e670 in __libc_start_main (main=0x424090 <main>, argc=11, argv=0x7ffd3d286b58, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, 
    stack_end=0x7ffd3d286b48) at ../csu/libc-start.c:289
#21 0x00000000004240c9 in _start () at ../sysdeps/x86_64/start.S:118