[RFA] Remove use of queue.h from gdbserver/event-loop.c

[RFA] Remove use of queue.h from gdbserver/event-loop.c

[Tom Tromey]

This removes a use of queue.h from gdbserver/event-loop.c, replacing
it with std::queue.

I was not completely sure whether std::queue is even that useful.
Perhaps plain std::list could be used just as easily.

Tested by the buildbot.

gdb/gdbserver/ChangeLog
2018-06-07  Tom Tromey  <tom@tromey.com>

	* event-loop.c (gdb_event, gdb_event_p): Remove typedefs.  Don't
	declare queue.
	(event_queue): Use std::queue.
	(gdb_event_xfree): Remove.
	(initialize_event_loop, process_event, wait_for_event): Update.
---
 gdb/gdbserver/ChangeLog    |  8 ++++++++
 gdb/gdbserver/event-loop.c | 34 ++++++++++++----------------------
 2 files changed, 20 insertions(+), 22 deletions(-)

diff --git a/gdb/gdbserver/event-loop.c b/gdb/gdbserver/event-loop.c
index eec0bcf3af6..a3310a05c8b 100644
--- a/gdb/gdbserver/event-loop.c
+++ b/gdb/gdbserver/event-loop.c
@@ -19,7 +19,6 @@
 /* Based on src/gdb/event-loop.c.  */
 
 #include "server.h"
-#include "queue.h"
 
 #include <sys/types.h>
 #include "gdb_sys_time.h"
@@ -30,8 +29,8 @@
 #endif
 
 #include <unistd.h>
+#include <queue>
 
-typedef struct gdb_event gdb_event;
 typedef int (event_handler_func) (gdb_fildes_t);
 
 /* Tell create_file_handler what events we are interested in.  */
@@ -40,8 +39,7 @@ typedef int (event_handler_func) (gdb_fildes_t);
 #define GDB_WRITABLE	(1<<2)
 #define GDB_EXCEPTION	(1<<3)
 
-/* Events are queued by calling 'QUEUE_enque (gdb_event_p, event_queue,
-   file_event_ptr)' and serviced later
+/* Events are queued by on the event_queue and serviced later
    on by do_one_event.  An event can be, for instance, a file
    descriptor becoming ready to be read.  Servicing an event simply
    means that the procedure PROC will be called.  We have 2 queues,
@@ -52,14 +50,14 @@ typedef int (event_handler_func) (gdb_fildes_t);
    descriptor whose state change generated the event, plus doing other
    cleanups and such.  */
 
-typedef struct gdb_event
+struct gdb_event
   {
     /* Procedure to call to service this event.  */
     event_handler_func *proc;
 
     /* File descriptor that is ready.  */
     gdb_fildes_t fd;
-  } *gdb_event_p;
+  };
 
 /* Information about each file descriptor we register with the event
    loop.  */
@@ -89,9 +87,9 @@ typedef struct file_handler
   }
 file_handler;
 
-DECLARE_QUEUE_P(gdb_event_p);
-static QUEUE(gdb_event_p) *event_queue = NULL;
-DEFINE_QUEUE_P(gdb_event_p);
+typedef gdb::unique_xmalloc_ptr<gdb_event> gdb_event_up;
+
+static std::queue<gdb_event_up, std::list<gdb_event_up>> event_queue;
 
 /* Gdb_notifier is just a list of file descriptors gdb is interested
    in.  These are the input file descriptor, and the target file
@@ -146,18 +144,9 @@ static struct
   }
 callback_list;
 
-/* Free EVENT.  */
-
-static void
-gdb_event_xfree (struct gdb_event *event)
-{
-  xfree (event);
-}
-
 void
 initialize_event_loop (void)
 {
-  event_queue = QUEUE_alloc (gdb_event_p, gdb_event_xfree);
 }
 
 /* Process one event.  If an event was processed, 1 is returned
@@ -173,13 +162,14 @@ process_event (void)
      proc function could end up jumping out to the caller of this
      function.  In that case, we would have on the event queue an
      event which has been processed, but not deleted.  */
-  if (!QUEUE_is_empty (gdb_event_p, event_queue))
+  if (!event_queue.empty ())
     {
-      gdb_event *event_ptr = QUEUE_deque (gdb_event_p, event_queue);
+      gdb_event_up event_ptr = std::move (event_queue.front ());
+      event_queue.pop ();
+
       event_handler_func *proc = event_ptr->proc;
       gdb_fildes_t fd = event_ptr->fd;
 
-      gdb_event_xfree (event_ptr);
       /* Now call the procedure associated with the event.  */
       if ((*proc) (fd))
 	return -1;
@@ -522,7 +512,7 @@ wait_for_event (void)
 	{
 	  gdb_event *file_event_ptr = create_file_event (file_ptr->fd);
 
-	  QUEUE_enque (gdb_event_p, event_queue, file_event_ptr);
+	  event_queue.emplace (file_event_ptr);
 	}
       file_ptr->ready_mask = mask;
     }
-- 
2.13.6

Re: [RFA] Remove use of queue.h from gdbserver/event-loop.c

[Simon Marchi]

On 2018-06-07 22:55, Tom Tromey wrote:
> This removes a use of queue.h from gdbserver/event-loop.c, replacing
> it with std::queue.
> 
> I was not completely sure whether std::queue is even that useful.
> Perhaps plain std::list could be used just as easily.

In the end it probably compiles down to the same thing, since std::queue 
is just a wrapper around the underlying container.  The std::queue would 
probably be useful if we wanted to swap the underlying container type 
without changing the code that uses the queue.  I'm fine either way.

Simon

Re: [RFA] Remove use of queue.h from gdbserver/event-loop.c

[Tom Tromey]

>>>>> "Simon" == Simon Marchi <simon.marchi@polymtl.ca> writes:

Simon> On 2018-06-07 22:55, Tom Tromey wrote:
>> This removes a use of queue.h from gdbserver/event-loop.c, replacing
>> it with std::queue.
>> 
>> I was not completely sure whether std::queue is even that useful.
>> Perhaps plain std::list could be used just as easily.

Simon> In the end it probably compiles down to the same thing, since
Simon> std::queue is just a wrapper around the underlying container.  The
Simon> std::queue would probably be useful if we wanted to swap the
Simon> underlying container type without changing the code that uses the
Simon> queue.  I'm fine either way.

In this particular case, I think any future change to the data structure
is likely to be pretty easy even without the queue wrapper.

Tom