valgrind ./switcher_danfysik
==26831== Memcheck, a memory error detector
==26831== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==26831== Using Valgrind-3.15.0 and LibVEX; rerun with -h for copyright info
==26831== Command: ./switcher_danfysik
==26831==
Opened successfully /dev/ttyUSB0
==26831== Warning: ignored attempt to set SIGKILL handler in sigaction();
==26831==          the SIGKILL signal is uncatchable
==26831== Warning: ignored attempt to set SIGSTOP handler in sigaction();
==26831==          the SIGSTOP signal is uncatchable
==26831== Invalid read of size 8
==26831==    at 0x5332AB2: XtIsSubclass (in /usr/lib64/libXt.so.6.0.0)
==26831==    by 0x407A41: xs_wprintf (switcher_danfysik.c:1517)
==26831==    by 0x402FFB: main (switcher_danfysik.c:415)
==26831==  Address 0x8 is not stack'd, malloc'd or (recently) free'd
==26831==
==26831==
==26831== Process terminating with default action of signal 11 (SIGSEGV)
==26831==  Access not within mapped region at address 0x8
==26831==    at 0x5332AB2: XtIsSubclass (in /usr/lib64/libXt.so.6.0.0)
==26831==    by 0x407A41: xs_wprintf (switcher_danfysik.c:1517)
==26831==    by 0x402FFB: main (switcher_danfysik.c:415)
==26831==  If you believe this happened as a result of a stack
==26831==  overflow in your program's main thread (unlikely but
==26831==  possible), you can try to increase the size of the
==26831==  main thread stack using the --main-stacksize= flag.
==26831==  The main thread stack size used in this run was 8388608.
==26831==
==26831== HEAP SUMMARY:
==26831==     in use at exit: 268,444 bytes in 1,823 blocks
==26831==   total heap usage: 3,085 allocs, 1,262 frees, 413,576 bytes allocated
==26831==
==26831== LEAK SUMMARY:
==26831==    definitely lost: 0 bytes in 0 blocks
==26831==    indirectly lost: 0 bytes in 0 blocks
==26831==      possibly lost: 10,310 bytes in 96 blocks
==26831==    still reachable: 258,134 bytes in 1,727 blocks
==26831==         suppressed: 0 bytes in 0 blocks
==26831== Rerun with --leak-check=full to see details of leaked memory
==26831==
==26831== For lists of detected and suppressed errors, rerun with: -s
==26831== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)
Segmentation fault (core dumped)