adts: DynHashTbl: safely handle calling clear() right before dtor

vfs: remove second call to tree_init (now done by vfs_mount)
vfs_tree: fix memory leak due to not destroying root node. commented and
armor-plated things while at it.

This was SVN commit r3647.

source/lib/adts.h

@@ -115,8 +115,13 @@ public:
 
 	void clear()
 	{
-		free(tbl);
-		tbl = 0;
+		// note: users might call clear() right before the dtor runs,
+		// so safely handling calling this twice.
+		if(tbl)
+		{
+			free(tbl);
+			tbl = 0;
+		}
 		num_entries = 0;
 		// rationale: must not set to 0 because expand_tbl only doubles the size.
 		// don't keep the previous size because it may have become huge and

source/lib/res/file/vfs.cpp

@@ -782,7 +782,6 @@ void vfs_display()
 // splitting this into a separate function.
 static void vfs_init_once(void)
 {
-	tree_init();
 	mount_init();
 }
 
@@ -805,5 +804,4 @@ void vfs_shutdown()
 {
 	trace_shutdown();
 	mount_shutdown();
-	tree_shutdown();
 }

source/lib/res/file/vfs_mount.cpp

@@ -617,7 +617,6 @@ LibError vfs_mount(const char* V_mount_point, const char* P_real_path, int flags
 LibError mount_rebuild()
 {
 	tree_clear();
-	tree_init();
 	remount_all();
 	return ERR_OK;
 }
@@ -677,7 +676,7 @@ void mount_init()
 
 void mount_shutdown()
 {
-	tree_clear();
+	tree_shutdown();
 	mount_unmount_all();
 }
 

source/lib/res/file/vfs_tree.cpp

@@ -420,30 +420,39 @@ static LibError lookup(TDir* td, const char* path, uint flags, TNode** pnode)
 //
 //////////////////////////////////////////////////////////////////////////////
 
+// this is a pointer to node_alloc-ed memory instead of a static TDir for
+// 2 reasons:
+// - no NLSO shutdown order issues; validity is well defined
+//   (namely between tree_init and tree_shutdown)
+// - bonus: tree_init can use it when checking if called twice.
+//
+//
 static TDir* tree_root;
 
-// rationale: can't do this in tree_shutdown - we'd leak at exit.
-// calling from tree_add* is ugly as well, so require manual init.
+
+// establish a root node and prepare node_allocator for use.
+//
+// rationale: calling this from every tree_add* is ugly, so require
+// manual init.
 void tree_init()
 {
+	// must not call more than once without intervening tree_shutdown
+	debug_assert(!tree_root);
+
 	node_init();
 
+#include "nommgr.h"	// placement new
 	void* mem = node_alloc();
 	if(mem)
-	{
-#include "nommgr.h"
 		tree_root = new(mem) TDir("", "");
 #include "mmgr.h"
-	}
-}
-
-
-void tree_shutdown()
-{
-	node_shutdown();
 }
 
 
+// empty all directories and free their memory.
+// however, node_allocator's DynArray still remains initialized and
+// the root directory is usable (albeit empty).
+// use when remounting.
 void tree_clear()
 {
 	tree_root->clearR();
@@ -451,6 +460,26 @@ void tree_clear()
 }
 
 
+// shut down entirely; destroys node_allocator. any further use after this
+// requires another tree_init.
+void tree_shutdown()
+{
+	// tree_shutdown should be preceded by tree_init, so ought to be valid.
+	debug_assert(tree_root);
+
+	// careful! do not call tree_clear because it will un-map all
+	// node memory, which would cause the dtor below to fail.
+	tree_root->clearR();
+
+	// we've still got to destroy the root node (otherwise its
+	// hash table will leak).
+	tree_root->~TDir();
+	tree_root = 0;
+
+	node_shutdown();
+}
+
+
 // write a representation of the VFS tree to stdout.
 void tree_display()
 {

source/lib/res/file/vfs_tree.h

@@ -26,14 +26,19 @@ class TDir;
 #include "vfs_mount.h"	// Mount
 
 
-
+// establish a root node and prepare node_allocator for use.
 extern void tree_init();
+
+// shut down entirely; destroys node_allocator. any further use after this
+// requires another tree_init.
 extern void tree_shutdown();
 
 extern void tree_display();
 
-// empties the tree and frees all resources. this is used when
-// rebuilding VFS and on exit.
+// empty all directories and free their memory.
+// however, node_allocator's DynArray still remains initialized and
+// the root directory is usable (albeit empty).
+// use when remounting.
 extern void tree_clear();
 
 extern time_t tree_most_recent_mtime();