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

[Simon Marchi <simark at sourceware dot org>]

https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=28addb40c77db5a5873172b62b6b7b43e5e05014

commit 28addb40c77db5a5873172b62b6b7b43e5e05014
Author: Simon Marchi <simon.marchi@ericsson.com>
Date:   Tue May 17 17:07:20 2016 -0400

    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:
---
 gdb/ChangeLog      | 6 ++++++
 gdb/mi/mi-interp.c | 2 +-
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index a06b860..188a2db 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,11 @@
 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
 	* mi/mi-main.c (run_one_inferior): Use run target to determine
 	whether to run async or not.
diff --git a/gdb/mi/mi-interp.c b/gdb/mi/mi-interp.c
index b37dc96..0fe19af 100644
--- 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);