try this

Author: jhawthorn

gc/default/default.c

@@ -467,7 +467,7 @@ enum gc_mode {
 typedef struct rb_objspace {
     struct {
         alignas(64) size_t increase;
-        size_t limit;
+        alignas(64) size_t limit;
 #if MALLOC_ALLOCATED_SIZE
         size_t allocated_size;
         size_t allocations;
@@ -587,7 +587,7 @@ typedef struct rb_objspace {
 
 #if RGENGC_ESTIMATE_OLDMALLOC
         alignas(64) size_t oldmalloc_increase;
-        size_t oldmalloc_increase_limit;
+        alignas(64) size_t oldmalloc_increase_limit;
 #endif
 
 #if RGENGC_CHECK_MODE >= 2