fix UPER BIT STRING trailer encoding

skeletons/BIT_STRING.c

@@ -487,17 +487,20 @@ BIT_STRING_encode_uper(const asn_TYPE_descriptor_t *td,
 
     if(csiz->effective_bits >= 0 && !inext) {
         int add_trailer = (ssize_t)size_in_bits < csiz->lower_bound;
-        ASN_DEBUG("Encoding %zu bytes (%ld), length in %d bits", st->size,
-                  size_in_bits - csiz->lower_bound, csiz->effective_bits);
+        ASN_DEBUG(
+            "Encoding %zu bytes (%ld), length (in %d bits) trailer %d; actual "
+            "value %zd",
+            st->size, size_in_bits - csiz->lower_bound, csiz->effective_bits,
+            add_trailer,
+            add_trailer ? 0 : (ssize_t)size_in_bits - csiz->lower_bound);
         ret = per_put_few_bits(
-            po,
-            add_trailer ? csiz->lower_bound : (ssize_t)size_in_bits - csiz->lower_bound,
+            po, add_trailer ? 0 : (ssize_t)size_in_bits - csiz->lower_bound,
             csiz->effective_bits);
         if(ret) ASN__ENCODE_FAILED;
         ret = per_put_many_bits(po, st->buf, size_in_bits);
         if(ret) ASN__ENCODE_FAILED;
         if(add_trailer) {
-            static uint8_t zeros[16];
+            static const uint8_t zeros[16];
             size_t trailing_zero_bits = csiz->lower_bound - size_in_bits;
             while(trailing_zero_bits > 0) {
                 if(trailing_zero_bits > 8 * sizeof(zeros)) {
@@ -623,6 +626,7 @@ BIT_STRING_random_fill(const asn_TYPE_descriptor_t *td, void **sptr,
     for(b = buf; b < bend; b++) {
         *(uint8_t *)b = asn_random_between(0, 255);
     }
+    *b = 0; /* Zero-terminate just in case. */
 
     if(*sptr) {
         st = *sptr;