make ext/coverage ASAN friendly

ext/coverage/coverage.c

@@ -11,6 +11,7 @@
 #include "gc.h"
 #include "internal/hash.h"
 #include "internal/thread.h"
+#include "internal/sanitizers.h"
 #include "ruby.h"
 #include "vm_core.h"
 
@@ -150,6 +151,9 @@ method_coverage_i(void *vstart, void *vend, size_t stride, void *data)
     VALUE ncoverages = *(VALUE*)data, v;
 
     for (v = (VALUE)vstart; v != (VALUE)vend; v += stride) {
+        void *poisoned = asan_poisoned_object_p(v);
+        asan_unpoison_object(v, false);
+
 	if (RB_TYPE_P(v, T_IMEMO) && imemo_type(v) == imemo_ment) {
 	    const rb_method_entry_t *me = (rb_method_entry_t *) v;
 	    VALUE path, first_lineno, first_column, last_lineno, last_column;
@@ -189,6 +193,10 @@ method_coverage_i(void *vstart, void *vend, size_t stride, void *data)
 		rb_hash_aset(methods, key, rcount);
 	    }
 	}
+
+        if (poisoned) {
+            asan_poison_object(v);
+        }
     }
     return 0;
 }