RFR: 8234779: Provide idiom for declaring classes noncopyable

[Stefan Karlsson]

Hi Kim,

On 2019-11-27 01:18, Kim Barrett wrote:
> Please review this change that adds a new macro NONCOPYABLE, for
> declaring a class to be noncopyable.  This change also modifies a
> bunch of classes to use the new macro.  Most of those classes already
> included equivalent code, and we're just replacing that with uses of
> the macro.
Did you consider doing something like this instead of using this macro?

diff --git a/src/hotspot/share/runtime/semaphore.hpp 
b/src/hotspot/share/runtime/semaphore.hpp
--- a/src/hotspot/share/runtime/semaphore.hpp
+++ b/src/hotspot/share/runtime/semaphore.hpp
@@ -44,8 +44,7 @@
    SemaphoreImpl _impl;

    // Prevent copying and assignment of Semaphore instances.
-  Semaphore(const Semaphore&);
-  Semaphore& operator=(const Semaphore&);
+  NonCopyable   _copy_poison;

   public:
    Semaphore(uint value = 0) : _impl(value) {}
@@ -60,4 +59,10 @@
    void wait_with_safepoint_check(JavaThread* thread);
  };

+void test_copy_semaphore() {
+  Semaphore s;
+  Semaphore sc1(s);
+  Semaphore sc2; sc2 = s;
+}
+
  #endif // SHARE_RUNTIME_SEMAPHORE_HPP
diff --git a/src/hotspot/share/utilities/globalDefinitions.hpp 
b/src/hotspot/share/utilities/globalDefinitions.hpp
--- a/src/hotspot/share/utilities/globalDefinitions.hpp
+++ b/src/hotspot/share/utilities/globalDefinitions.hpp
@@ -1193,5 +1193,13 @@
    return k0 == k1;
  }

+class NonCopyable {
+private:
+  NonCopyable(NonCopyable const&);
+  NonCopyable& operator=(NonCopyable const&);
+
+public:
+  NonCopyable() {}
+};

  #endif // SHARE_UTILITIES_GLOBALDEFINITIONS_HPP

Thanks,
StefanK

> 
> (A few classes in PtrQueue.hpp that weren't previously made
> noncopyable but should have been are now also using the NONCOPYABLE
> macro.)
> 
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8234779
> 
> Webrev:
> https://cr.openjdk.java.net/~kbarrett/8234779/open.00/
> 
> Testing:
> mach5 tier1
> 
> linux fastdebug builds for the following:
> 1. platforms: aarch64, arm32, ppc64le, s390x, zero.
> 2. x86_64 with shenandoah included.
> 3. x86_64 minimal configuration.
>