Suppress warnings no inline ruby debug (#3107)

* Suppress unused warnings occurred due to -fno-inline

* Suppress warning occurred due to RUBY_DEBUG=1

array.c

@@ -5269,7 +5269,7 @@ static VALUE
 flatten(VALUE ary, int level)
 {
     long i;
-    VALUE stack, result, tmp, elt, vmemo;
+    VALUE stack, result, tmp = 0, elt, vmemo;
     st_table *memo;
     st_data_t id;
 

ext/stringio/stringio.c

@@ -1532,7 +1532,6 @@ strio_read(int argc, VALUE *argv, VALUE self)
     long len;
     int binary = 0;
 
-    rb_check_arity(argc, 0, 2);
     switch (argc) {
       case 2:
 	str = argv[1];
@@ -1572,6 +1571,8 @@ strio_read(int argc, VALUE *argv, VALUE self)
 	    len -= ptr->pos;
 	}
 	break;
+      default:
+        rb_error_arity(argc, 0, 2);
     }
     if (NIL_P(str)) {
 	rb_encoding *enc = binary ? rb_ascii8bit_encoding() : get_enc(ptr);

vm_insnhelper.h

@@ -140,7 +140,7 @@ CC_SET_FASTPATH(const struct rb_callcache *cc, vm_call_handler func, bool enable
 
 #if VM_CHECK_MODE > 0
 #define SETUP_CANARY() \
-    VALUE *canary; \
+    VALUE *canary = 0; \
     if (leaf) { \
         canary = GET_SP(); \
         SET_SV(vm_stack_canary); \