Use rvalue reference in thread_pool::post_task

Tankut's recent patches made me realize that thread_pool::post_task
should have used an rvalue reference for its parameter.  This patch
makes this change.

gdbsupport/ChangeLog
2021-04-30  Tom Tromey  <[email protected]>

	* thread-pool.cc (thread_pool::post_task): Update.
	* thread-pool.h (class thread_pool) <post_task>: Take rvalue
	reference to function.

Author: tromey

gdbsupport/ChangeLog

@@ -1,3 +1,9 @@
+2021-04-30  Tom Tromey  <[email protected]>
+
+	* thread-pool.cc (thread_pool::post_task): Update.
+	* thread-pool.h (class thread_pool) <post_task>: Take rvalue
+	reference to function.
+
 2021-04-27  Michael Weghorn  <[email protected]>
 	    Simon Marchi  <[email protected]>
 

gdbsupport/thread-pool.cc

@@ -130,9 +130,9 @@ thread_pool::set_thread_count (size_t num_threads)
 }
 
 std::future<void>
-thread_pool::post_task (std::function<void ()> func)
+thread_pool::post_task (std::function<void ()> &&func)
 {
-  std::packaged_task<void ()> t (func);
+  std::packaged_task<void ()> t (std::move (func));
   std::future<void> f = t.get_future ();
 
   if (m_thread_count == 0)

gdbsupport/thread-pool.h

@@ -58,7 +58,7 @@ class thread_pool
 
   /* Post a task to the thread pool.  A future is returned, which can
      be used to wait for the result.  */
-  std::future<void> post_task (std::function<void ()> func);
+  std::future<void> post_task (std::function<void ()> &&func);
 
 private: