From Prof Brian Ripley:

The gcc-SAN checks newly report:

• checking whether package ‘data.table’ can be installed ... [255s/258s]
  WARNING
  Found the following significant warnings:
  assign.c:665:9: warning: ‘memset’ writing 1 byte into a region of
  size 0 overflows the destination [-Wstringop-overflow=]

from (they use LTO)

gcc -fsanitize=address,undefined,bounds-strict -fno-omit-frame-pointer
-shared -g -O2 -Wall -pedantic -mtune=native -Wno-stringop-truncation
-Wno-alloc-size-larger-than -flto=10 -fpic -L/usr/local/lib64 -o
data.table.so assign.o between.o bmerge.o chmatch.o cj.o coalesce.o
dogroups.o fastmean.o fcast.o fifelse.o fmelt.o forder.o frank.o fread.o
freadR.o froll.o frollR.o frolladaptive.o fsort.o fwrite.o fwriteR.o
gsumm.o idatetime.o ijoin.o init.o inrange.o nafill.o negate.o
nqrecreateindices.o openmp-utils.o programming.o quickselect.o
rbindlist.o reorder.o shift.o snprintf.o subset.o transpose.o types.o
uniqlist.o utils.o vecseq.o wrappers.o -fopenmp -lz
assign.c: In function ‘assign’:
assign.c:665:9: warning: ‘memset’ writing 1 byte into a region of size 0
overflows the destination [-Wstringop-overflow=]
665 | memset(s5 + 2, '\0', 1);
| ^
lto1: note: destination object is likely at address zero
assign.c:665:9: warning: ‘memset’ writing 1 byte into a region of size 0
overflows the destination [-Wstringop-overflow=]
lto1: note: destination object is likely at address zero

Please fix ASAP.