spnego.c:1430:2: error: ‘len’ may be used uninitialized in this function on ARM

v9_16 and v9_11 (but not on main) produce a build warning on Debian 9-based Armbian with gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516 on Odroid HC1, a single board system (32-bit armv7l CPU). As we compile on this OS with the same compiler in the CI, where the warning does not manifest, it might be ARM-specific.

v9_16:

gcc  -include /export/data/bind9/config.h -I/export/data/bind9 -I../.. -I. -I../../lib/dns -Iinclude -I/export/data/bind9/lib/dns/include -I../../lib/dns/include     -I/export/data/bind9/lib/isc/include -I../../lib/isc -I../../lib/isc/include -I../../lib/isc/unix/include -I../../lib/isc/pthreads/include   -I/usr/include  -I/usr/include/json-c -I/usr/include/libxml2  -I/usr/include/arm-linux-gnueabihf   -DGSSAPI -DUSE_ISC_SPNEGO -DISC_MEM_DEFAULTFILL=1 -DISC_LIST_CHECKINIT=1 -fno-omit-frame-pointer -fno-optimize-sibling-calls -O1 -g -Wall -Wextra -pthread -fPIC  -W -Wall -Wmissing-prototypes -Wcast-qual -Wwrite-strings -Wformat -Wpointer-arith -Wno-missing-field-initializers -fno-strict-aliasing -Wshadow -Werror  -c spnego.c
spnego.c: In function ‘gss_init_sec_context_spnego’:
spnego.c:1430:2: error: ‘len’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  memmove(p, buf, buf_size);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
spnego.c:1510:9: note: ‘len’ was declared here
  size_t len;
         ^~~
cc1: all warnings being treated as errors

v9_11:

gcc  -I/export/data/bind9 -I../.. -I. -I../../lib/dns -Iinclude -I/export/data/bind9/lib/dns/include -I../../lib/dns/include -I/export/data/bind9/lib/isc/include -I../../lib/isc -I../../lib/isc/include -I../../lib/isc/unix/include -I../../lib/isc/pthreads/include -I../../lib/isc/noatomic/include  -I/usr/include  -D_REENTRANT -DUSE_MD5 -DOPENSSL -DGSSAPI -DUSE_ISC_SPNEGO -DISC_LIST_CHECKINIT=1 -D_GNU_SOURCE -fno-omit-frame-pointer -fno-optimize-sibling-calls -O1 -g -Wall -Wextra  -I/usr/include/libxml2   -fPIC  -W -Wall -Wmissing-prototypes -Wcast-qual -Wwrite-strings -Wformat -Wpointer-arith -fno-strict-aliasing -fno-delete-null-pointer-checks -Wshadow -Werror  -c spnego.c
spnego.c: In function ‘gss_init_sec_context_spnego’:
spnego.c:1438:2: error: ‘len’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
  memmove(p, buf, buf_size);
  ^~~~~~~~~~~~~~~~~~~~~~~~~
spnego.c:1521:9: note: ‘len’ was declared here
  size_t len;
         ^~~
cc1: all warnings being treated as errors