support/BPath: Flatten should work on empty BPath

BPath::Flatten() on an empty path returns B_OK in BeOS R5, just
writing an empty entry_ref to the povided buffer. The Haiku
implementation has some additional validation that causes B_NO_INIT to
be returned instead.

This patch attempts to recreate the same behavior of BeOS in this
situation.

* Don't check for initialization in BPath::Flatten(). Instead,
  just write an empty entry_ref to the provided buffer if the BPath is
  empty.
* Fix estimation of expected size when testing the return value of
  BPath::FlattenedSize().
* Clean up warning by removing unecessary forward-declaration of
  CppUnit::Test.

Change-Id: I88880cbb298bdcb594c9c8fef48314165c49e9e5
Reviewed-on: https://review.haiku-os.org/c/haiku/+/2115
Reviewed-by: Adrien Destugues <[email protected]>
Reviewed-by: Axel Dörfler <[email protected]>

src/kits/storage/Path.cpp

@@ -431,18 +431,18 @@ BPath::Flatten(void* buffer, ssize_t size) const
 		return flattenedSize;
 	if (size < flattenedSize)
 		return B_BAD_VALUE;
-	status_t status = InitCheck();
-	if (status != B_OK)
-		return status;
 
 	// convert the path to an entry_ref
 	BEntry entry;
 	entry_ref ref;
-	status = entry.SetTo(Path());
-	if (status == B_OK)
-		status = entry.GetRef(&ref);
-	if (status != B_OK)
-		return status;
+
+	if (Path() != NULL) {
+		status_t status = entry.SetTo(Path());
+		if (status == B_OK)
+			status = entry.GetRef(&ref);
+		if (status != B_OK)
+			return status;
+	}
 
 	// store the entry_ref in the buffer
 	flattened_entry_ref& fref = *(flattened_entry_ref*)buffer;

src/tests/kits/storage/PathTest.cpp

@@ -1352,8 +1352,8 @@ PathTest::FlattenableTest()
 		// flatten the path
 		struct flattened_ref { dev_t device; ino_t directory; char name[1]; };
 		size = path.FlattenedSize();
-		ssize_t expectedSize	// hehe, that's hacky ;-)
-			= (ssize_t)((flattened_ref*)NULL)->name + strlen(ref.name) + 1;
+		ssize_t expectedSize
+			= sizeof(dev_t) + sizeof(ino_t) + strlen(ref.name) + 1;
 		CPPUNIT_ASSERT( size ==  expectedSize);
 		CPPUNIT_ASSERT( path.Flatten(buffer, sizeof(buffer)) == B_OK );
 		// check the flattened data

src/tests/kits/storage/PathTest.h

@@ -8,8 +8,6 @@
 #include <StorageDefs.h>
 #include <SupportDefs.h>
 
-class CppUnit::Test;
-
 class PathTest : public BasicTest
 {
 public: