add a test which ensures that bit shift right is an arithmetic shift, not logical shift.

docs/mc-data-spec.md

@@ -39,13 +39,8 @@ Where \*.mca files are the newer variant.
 
 ### coordinate conversions
 ```c
-// block->chunk:
+return (x >> 4); // block->chunk
-return (x / 16) - sgn(x);
+return (x >> 5); // chunk->region
-return (x >> 4) - (x & 0x80000000);
-
-// chunk->region:
-return (x / 32) - sgn(x);
-return (x >> 5) - (x & 0x80000000);
 ```
 
 

test/dat.h

@@ -2,10 +2,12 @@
 
 #include "../src/util/conf.h"
 #include "../src/util/types.h"
+#include "t_arith.h"
 #include "t_conf.h"
 #include "test.h"
 
 testdat tests[] = {
+	{"ensure SAR",  test_sar,                NULL									    },
 	{"k=v",         test_procbuf,            &(struct test_procbuf){"key=val", "key", "val", 0}                              },
 	{"sometxt",     test_procbuf,            &(struct test_procbuf){"sometxt", "sometxt", "", CONF_ESYNTAX}                  },
 	{"comment",     test_procbuf,            &(struct test_procbuf){"# comment", "", "", CONF_ENODAT}                        },

test/t_arith.h

@@ -0,0 +1,8 @@
+#pragma once
+
+#include "test.h"
+
+int test_sar(void *dat) {
+	(void)dat;
+	return assert_true(-3 >> 5 == -1);
+}