[libc-commits] [libc] [libc] Add some checks to the mmap wrapper (PR #197694)

[Jeff Bailey via libc-commits]

================
@@ -41,3 +42,40 @@ TEST_F(LlvmLibcMMapTest, Error_InvalidSize) {
 
   EXPECT_THAT(LIBC_NAMESPACE::munmap(0, 0), Fails(EINVAL));
 }
+
+TEST_F(LlvmLibcMMapTest, FileOffsets) {
+  int fd = LIBC_NAMESPACE::memfd_create("mmap_test", MFD_CLOEXEC);
+  ASSERT_NE(fd, -1);
+  ASSERT_ERRNO_SUCCESS();
+  LIBC_NAMESPACE::cpp::scope_exit close_fd(
+      [&]() { ASSERT_THAT(LIBC_NAMESPACE::close(fd), Succeeds()); });
+
+  // Check that we can map a file from offset zero. This succeeds even though
+  // the file is empty.
+  void *addr = LIBC_NAMESPACE::mmap(nullptr, 47, PROT_READ,
+                                    MAP_ANONYMOUS | MAP_PRIVATE, fd, 0);
----------------
kaladron wrote:

Is the MAP_ANONYMOUS needed here if it's backed by a zero-length file?



https://github.com/llvm/llvm-project/pull/197694