What does
UndefinedBehaviorSanitizer:DEADLYSIGNAL
==752==ERROR: UndefinedBehaviorSanitizer: SEGV on unknown address 0x000000439000 (pc 0x000000428b5b bp 0x7ffdc38f56b0 sp 0x7ffdc38f5380 T752)
==752==The signal is caused by a READ memory access.
#0 0x428b5a in crack /root/sandbox/crack.c:70:35
#1 0x42804e in main /root/sandbox/crack.c:21:21
#2 0x7ff3677e0b96 in __libc_start_main /build/glibc-OTsEL5/glibc-2.27/csu/../csu/libc-start.c:310
#3 0x402b39 in _start (/root/sandbox/crack+0x402b39)
UndefinedBehaviorSanitizer can not provide additional info.
==752==ABORTING
mean? (It's obviously an error).