# ./configure --enable-ubsan --enable-asan
...
checking checking for ubsan... yes
checking for gcc support of -fsanitize=undefined... yes
checking for gcc support of -fsanitize=undefined... yes
checking checking for asan... yes
checking for gcc support of -fsanitize=address... yes
checking for gcc support of -fsanitize=address... yes
...
Tested autoconf changes:
make check
passes as well.Rest of changes LGTM.