Fix double prompt output after run control MI commands with mi-async on (PR 20045)

When you use a run control command (-exec-run, -exec-continue,
-exec-next, ...) with mi-async on, an extra (gdb) prompt is displayed:

  -exec-continue
  ^running
  *running,thread-id="all"
  (gdb)
  (gdb)

It doesn't seem to be a big problem for front-ends, since this behavior
started in gdb 7.9 and we haven't heard anything about that.  However,
it caused me some trouble while writing a test for PR 20039 [1].

The problem comes from an extra (gdb) prompt that we write when running
in mi-async off mode to emulate a past buggy behavior.  When executing a
run control command synchronously, previous gdbs always printed a prompt
right away, even though they are not ready to accept new MI commands
until the target stops.  Only at this time should they display a prompt.
But to keep backwards compatibility apparently, we print it anyway.
Since commit 198297aaf, the condition that decides whether we should
print that "bogus" prompt or not has become true, even when running with
mi-async on.  Since we already print a prompt at the end of the
asynchronous command execution, it results in two prompts for one
command.

The proposed fix is to call target_can_async_p instead of
target_is_async_p, to make the condition:

  if (!target_can_async_p () || sync_execution)
    ... show prompt ...

That shows the prompt if we are emulating a synchronous command on top
of an asynchronous target (sync_execution) or if the target simply can't
run asynchronously (!target_can_async_p ()).

Note that this code is changed and this bug fixed by Pedro's separate
console series, but I think it would be nice to have it fixed in the
mean time.

I ran the gdb.mi directory of the testsuite with mi-async on and off, I
didn't see any regressions.

gdb/ChangeLog:

	* mi/mi-main.c (mi_on_resume): Call target_can_async_p instead
	of target_is_async_p.

[1] https://sourceware.org/ml/gdb-patches/2016-05/msg00075.html

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 30c6e4bfcf227e6423828842cb1e617fd1aca29e..3ee9cb4f992b64e5228930dc5305ff59cfbd9724 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,9 @@
+2016-05-17  Simon Marchi  <simon.marchi@ericsson.com>
+
+       PR gdb/20045
+       * mi/mi-main.c (mi_on_resume): Call target_can_async_p instead
+       of target_is_async_p.
+
 2016-05-17  Simon Marchi  <simon.marchi@ericsson.com>
 
        PR gdb/18077

diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
index 8de0c34934dce5b7279e6c269e440b59e166f59b..3e8ac427544f0cc757771a2d91ac00d71fa96347 100644 (file)
--- a/gdb/mi/mi-interp.c
+++ b/gdb/mi/mi-interp.c
@@ -998,7 +998,7 @@ mi_on_resume (ptid_t ptid)
         for MI3, and may be removed even earlier.  SYNC_EXECUTION is
         checked here because we only need to emit a prompt if a
         synchronous command was issued when the target is async.  */
-      if (!target_is_async_p () || sync_execution)
+      if (!target_can_async_p () || sync_execution)
        fputs_unfiltered ("(gdb) \n", raw_stdout);
     }
   gdb_flush (raw_stdout);