bug#20843: 24.5; Profiler error: "Invalid sampling interval"

[Ken Brown <kbrown@cornell.edu>]

On 6/21/2015 10:56 AM, Eli Zaretskii wrote:
>> Date: Sat, 20 Jun 2015 17:47:21 -0400
>> From: Ken Brown <kbrown@cornell.edu>
>> CC: sva-news@mygooglest.com, 20843@debbugs.gnu.org
>>
>>> Then I guess the configure-time test for setitimer should also test
>>> for ITIMER_PROF.
>>
>> I'd be glad to give this a try, but I don't have any experience writing
>> autoconf macros.  Is there a standard macro to test whether a function
>> accepts a particular argument?  If not, can you (or anyone) point me to
>> an example that I can imitate?
>
> Actually, perhaps I misunderstood you: are you saying that Cygwin does
> have ITIMER_PROF defined in the appropriate header, but when setitimer
> is called with it, it always fails?

Yes.

> If so, we cannot test this at
> configure time, because it means we will have to run a program, which
> is not a good idea.
>
> So in that case, I think we should simply disable the CPU profiler on
> Cygwin using "#ifndef __CYGWIN__" or some such.

Done as commit 5fac0de.

>>>   Also, the diagnostics should be improved, as the
>>> wording is misleading in that case.
>>
>> As it stands, profiler-cpu-start reports "Invalid sampling interval"
>> whenever setup_cpu_timer fails to start the timer, regardless of the
>> reason.  I'll try to improve this.
>
> Yes, please.

How's this:

--- a/src/profiler.c
+++ b/src/profiler.c
@@ -250,6 +250,8 @@ deliver_profiler_signal (int signal)
    deliver_process_signal (signal, handle_profiler_signal);
  }

+static bool sampling_interval_ok;
+
  static enum profiler_cpu_running
  setup_cpu_timer (Lisp_Object sampling_interval)
  {
@@ -258,11 +260,13 @@ setup_cpu_timer (Lisp_Object sampling_interval)
    struct timespec interval;
    int billion = 1000000000;

-  if (! RANGED_INTEGERP (1, sampling_interval,
-                        (TYPE_MAXIMUM (time_t) < EMACS_INT_MAX / billion
-                         ? ((EMACS_INT) TYPE_MAXIMUM (time_t) * billion
-                            + (billion - 1))
-                         : EMACS_INT_MAX)))
+  sampling_interval_ok =
+    RANGED_INTEGERP (1, sampling_interval,
+                    (TYPE_MAXIMUM (time_t) < EMACS_INT_MAX / billion
+                     ? ((EMACS_INT) TYPE_MAXIMUM (time_t) * billion
+                        + (billion - 1))
+                     : EMACS_INT_MAX));
+  if (! sampling_interval_ok)
      return NOT_RUNNING;

    current_sampling_interval = XINT (sampling_interval);
@@ -338,7 +342,12 @@ See also `profiler-log-size' and 
`profiler-max-stack-depth'.  */)

    profiler_cpu_running = setup_cpu_timer (sampling_interval);
    if (! profiler_cpu_running)
-    error ("Invalid sampling interval");
+    {
+      if (! sampling_interval_ok)
+       error ("Invalid sampling interval");
+      else
+       error ("Unable to start profiler timer");
+    }

    return Qt;
  }

Ken