#2432 SEGV on eval_plots

[liuchenyifan]

gnuplot 5.5 (last modified in 9.18) on centos linux 7.7.1908

==4971== ERROR: AddressSanitizer: SEGV on unknown address 0x00000000000c (pc 0x00000068ac95 sp 0x7ffd6de9fec0 bp 0x000000000000 T0)
AddressSanitizer can not provide additional info.
#0 0x68ac94 (/root/uniafl_evaluation/asan_program/gnuplot+0x68ac94)
#1 0x463bc3 (/root/uniafl_evaluation/asan_program/gnuplot+0x463bc3)
#2 0x459f6c (/root/uniafl_evaluation/asan_program/gnuplot+0x459f6c)
#3 0x61b63b (/root/uniafl_evaluation/asan_program/gnuplot+0x61b63b)
#4 0x40772e (/root/uniafl_evaluation/asan_program/gnuplot+0x40772e)
#5 0x7f2728760554 (/usr/lib64/libc-2.17.so+0x22554)
#6 0x4084ec (/root/uniafl_evaluation/asan_program/gnuplot+0x4084ec)
==4971== ABORTING

information below from valgrind:

==4974== Memcheck, a memory error detector
==4974== Copyright (C) 2002-2017, and GNU GPL'd, by Julian Seward et al.
==4974== Using Valgrind-3.16.1 and LibVEX; rerun with -h for copyright info
==4974== Command: /root/pfuzz-new/p-fuzz/pfcon/programs/gnuplot ./bugs/SEGV_evalplots
==4974==
==4974== Invalid read of size 4
==4974== at 0x61D710: eval_plots (plot2d.c:3464)
==4974== by 0x44BB88: plot_command (command.c:1897)
==4974== by 0x4411AB: command (command.c:659)
==4974== by 0x4411AB: do_line (command.c:429)
==4974== by 0x5CD14B: load_file (misc.c:335)
==4974== by 0x406416: main (plot.c:636)
==4974== Address 0xc is not stack'd, malloc'd or (recently) free'd
==4974==
==4974==
==4974== Process terminating with default action of signal 11 (SIGSEGV)
==4974== Access not within mapped region at address 0xC
==4974== at 0x61D710: eval_plots (plot2d.c:3464)
==4974== by 0x44BB88: plot_command (command.c:1897)
==4974== by 0x4411AB: command (command.c:659)
==4974== by 0x4411AB: do_line (command.c:429)
==4974== by 0x5CD14B: load_file (misc.c:335)
==4974== by 0x406416: main (plot.c:636)
==4974== If you believe this happened as a result of a stack
==4974== overflow in your program's main thread (unlikely but
==4974== possible), you can try to increase the size of the
==4974== main thread stack using the --main-stacksize= flag.
==4974== The main thread stack size used in this run was 8388608.
==4974==
==4974== HEAP SUMMARY:
==4974== in use at exit: 34,611 bytes in 173 blocks
==4974== total heap usage: 290 allocs, 117 frees, 199,668 bytes allocated
==4974==
==4974== LEAK SUMMARY:
==4974== definitely lost: 0 bytes in 0 blocks
==4974== indirectly lost: 0 bytes in 0 blocks
==4974== possibly lost: 0 bytes in 0 blocks
==4974== still reachable: 34,611 bytes in 173 blocks
==4974== suppressed: 0 bytes in 0 blocks
==4974== Rerun with --leak-check=full to see details of leaked memory
==4974==
==4974== For lists of detected and suppressed errors, rerun with: -s
==4974== ERROR SUMMARY: 1 errors from 1 contexts (suppressed: 0 from 0)