RFR(S) 8227868: jinfo and jstack can fail converting UTF8 output to strings

[Severin Gehwolf]

On Thu, 2019-07-18 at 10:07 +0000, Schmelter, Ralf wrote:
> Please review this fix. It applies the same correction to jstack and
> jinfo which was already applied to jcmd. To avoid code duplication, I
> moved the actual code to a utility class.
> 
> webrev: 
> http://cr.openjdk.java.net/~rschmelter/webrevs/8227868/webrev.0/
> bugreport: https://bugs.openjdk.java.net/browse/JDK-8227868

+    /**
+     * Reads characters in UTF-8 format from the input stream and prints them
+     * with the given print stream. Closes the input stream before it returns.
+     *
+     * @return The number of printed characters.
+     */
+    public static long drainUTF8(InputStream is, PrintStream ps) throws IOException {
+        long result = 0;
+
+        try (BufferedInputStream bis = new BufferedInputStream(is);
+             InputStreamReader isr = new InputStreamReader(bis, "UTF-8")) {
+            char c[] = new char[8192];
+            int n;
+
+            do {
+                n = isr.read(c);
+
+                if (n > 0) {
+                    result += n;
+                    System.out.print(n == c.length ? c : Arrays.copyOf(c, n));
+                }

If I read this right, then the method doesn't do what it claims it
does. It's printing to System.out unconditionally instead of to 'ps'.
What am I missing?

Would it be possible to add regression tests for this? Along the lines
of test/jdk/sun/tools/jstack/BasicJStackTest.java

Thanks,
Severin