print.c: warning: null destination pointer

On Fedora 33 with custom experimental gcc snapshot version 11.0.0 20210124 I get the following warning:

/opt/gcc-latest/bin/gcc  -I/home/newman/isc/ws/bind9 -I../.. -I./unix/include -I. -I./include -I./include -I/home/newman/isc/ws/bind9/lib/isc/include -I../../lib/isc -I../../lib/isc/include -I../../lib/isc/unix/include -I../../lib/isc/pthreads/include -I../../lib/isc/x86_32/include  -D_REENTRANT  -D_GNU_SOURCE -fno-omit-frame-pointer -fno-optimize-sibling-calls -O1 -g -Wall -Wextra -fsanitize=address,undefined -DISC_MEM_USE_INTERNAL_MALLOC=0  -I/usr/include/libxml2    -fPIC  -W -Wall -Wmissing-prototypes -Wcast-qual -Wwrite-strings -Wformat -Wpointer-arith -fno-strict-aliasing -fno-delete-null-pointer-checks  -c print.c
/opt/gcc-latest/bin/gcc  -I/home/newman/isc/ws/bind9 -I../.. -I./unix/include -I. -I./include -I./include -I/home/newman/isc/ws/bind9/lib/isc/include -I../../lib/isc -I../../lib/isc/include -I../../lib/isc/unix/include -I../../lib/isc/pthreads/include -I../../lib/isc/x86_32/include  -D_REENTRANT  -D_GNU_SOURCE -fno-omit-frame-pointer -fno-optimize-sibling-calls -O1 -g -Wall -Wextra -fsanitize=address,undefined -DISC_MEM_USE_INTERNAL_MALLOC=0  -I/usr/include/libxml2    -fPIC  -W -Wall -Wmissing-prototypes -Wcast-qual -Wwrite-strings -Wformat -Wpointer-arith -fno-strict-aliasing -fno-delete-null-pointer-checks  \
	-DVERSION=\"9.11.27\" \
	-DLIBINTERFACE=161 \
	-DLIBREVISION=4 \
	-DLIBAGE=0 \
	-c ./version.c
print.c: In function ‘lwres__print_sprintf’:
print.c:32:9: warning: null destination pointer [-Wformat-overflow=]
   32 |         vsprintf(str, format, ap);
      |         ^~~~~~~~~~~~~~~~~~~~~~~~~