Merge "Add a unit test for %n."

tests/stdio_test.cpp

@@ -183,6 +183,18 @@ TEST(stdio, printf_ssize_t) {
   snprintf(buf, sizeof(buf), "%zd", v);
 }
 
+#if !defined(__GLIBC__)
+TEST(stdio, snprintf_n_format_specifier_not_implemented) {
+  char buf[32];
+  int i = 0;
+  // We deliberately don't implement %n, so it's treated like
+  // any other unrecognized format specifier.
+  EXPECT_EQ(5, snprintf(buf, sizeof(buf), "a %n b", &i));
+  EXPECT_EQ(0, i);
+  EXPECT_STREQ("a n b", buf);
+}
+#endif
+
 TEST(stdio, snprintf_smoke) {
   char buf[BUFSIZ];