Re: 8193072: File.delete() should remove its path from DeleteOnExitHook.files

[Ivan Gerasimov]

Hi Brian!

I believe this would introduce a behavior change in a scenario lile:
File f = ...;
f.deleteOnExit();
f.delete();
f.createNewFile();
I.e. when the with the same name is recreated.  Current behavior is to 
unlink such a file before exiting, no matter if it were explicitly 
deleted and then recreated or not.

With kind regards,
Ivan


On 7/8/19 1:11 PM, Brian Burkhalter wrote:
https://bugs.openjdk.java.net/browse/JDK-8193072 
<https://bugs.openjdk.java.net/browse/JDK-8193072>

There does appear to be a memory leak of sorts if one does something like

—

File[] files;
for (int i = 0; i < largeNumber; i++) {
     files[i] = File.createTempFile(“blah”, null);
     files[i].deleteOnExit();
}

// do something

for (int i = 0; i < largeNumber; i++) {
     files[i].delete();
}

// do something else before shutdown

—

The LinkedHashSet in DeleteOnExitHook will contain at least largeNumber Files 
until the VM shuts down even though the files were deleted.

The potential change is included below. The additional call to 
DeleteOnExitHook.remove() in File.delete() does not appear to have a measurable 
performance impact, at least trivially and in isolation.

Thanks,

Brian

--- a/src/java.base/share/classes/java/io/DeleteOnExitHook.java
+++ b/src/java.base/share/classes/java/io/DeleteOnExitHook.java
@@ -64,6 +64,15 @@
          files.add(file);
      }
  
+    static synchronized void remove(String file) {
+        if(files == null) {
+            // DeleteOnExitHook is running. Too late to remove a file
+            throw new IllegalStateException("Shutdown in progress");
+        }
+
+        files.remove(file);
+    }
+
      static void runHooks() {
          LinkedHashSet<String> theFiles;
  
--- a/src/java.base/share/classes/java/io/File.java
+++ b/src/java.base/share/classes/java/io/File.java
@@ -1050,6 +1050,7 @@
          if (isInvalid()) {
              return false;
          }
+        DeleteOnExitHook.remove(path);
          return fs.delete(this);
      }


--
With kind regards,
Ivan Gerasimov