Fix dup2 in the case where the two fds are equal.
dup3's behavior differs from dup2 in this case, so we need to paper
over that in the C library.
Change-Id: I313cd6f226db5e237f61866f324c5ecdd12bf762
diff --git a/tests/unistd_test.cpp b/tests/unistd_test.cpp
index f5c0524..f54a461 100644
--- a/tests/unistd_test.cpp
+++ b/tests/unistd_test.cpp
@@ -801,3 +801,22 @@
VERIFY_SYSCONF_NOT_SUPPORT(_SC_XOPEN_UUCP);
#endif // defined(__BIONIC__)
}
+
+TEST(unistd, dup2_same) {
+ // POSIX says of dup2:
+ // If fildes2 is already a valid open file descriptor ...
+ // [and] fildes is equal to fildes2 ... dup2() shall return
+ // fildes2 without closing it.
+ // This isn't true of dup3(2), so we need to manually implement that.
+
+ // Equal and valid.
+ int fd = open("/proc/version", O_RDONLY);
+ ASSERT_TRUE(fd != -1);
+ ASSERT_EQ(fd, dup2(fd, fd));
+ ASSERT_EQ(0, close(fd)); // Check that dup2 didn't close fd.
+
+ // Equal, but invalid.
+ errno = 0;
+ ASSERT_EQ(-1, dup2(fd, fd));
+ ASSERT_EQ(EBADF, errno);
+}