make sure last_log changes, but isn't null on append

test/append-test-log.c

@@ -21,6 +21,7 @@
 
 #include <u.h>
 #include <libc.h>
+#include <stdio.h>
 
 #include "../9unit.h"
 #include "util.h"
@@ -31,6 +32,14 @@
 static void append_to_empty(TestState *);
 static void append_to_existing(TestState *);
 
+static void chk_ptr_chg(
+	TestState *,
+	const char *,
+	const char *,
+	const void *,
+	const void *
+);
+
 // Public Functions
 
 void
@@ -105,6 +114,50 @@ append_to_existing(TestState *s)
 		test.first_log,
 		&first
 	);
+
+	// last should change
+	print("\t\tlast_log\n");
+	chk_ptr_chg(
+		s,
+		"\t\t\t",
+		"ERROR: append_test_log(): last_log:",
+		test.last_log,
+		&second
+	);
+}
+
+static void
+chk_ptr_chg(
+	TestState *s,
+	const char *prefix,
+	const char *context,
+	const void *actual,
+	const void *prohibited
+)
+{
+	char str[STR_BUF_SIZE];
+
+	// make sure it's changed
+	print(prefix);
+	print("changed\n");
+	snprintf(str, STR_BUF_SIZE, "%s changed:", context);
+	chk_ptr_ne(
+		s,
+		str,
+		actual,
+		prohibited
+	);
+
+	// make sure it's not null
+	print(prefix);
+	print("not null\n");
+	snprintf(str, STR_BUF_SIZE, "%s not null:", context);
+	chk_ptr_ne(
+		s,
+		str,
+		actual,
+		0
+	);
 }
 
 //jl