Add timestamps to "maint time" output

Currently "maint time" will print the amount of time a command took.
Sometimes, though, it's useful to have a timestamp as well -- for
example if one is correlating a gdb log with some other log.

This patch adds a timestamp to the start and end of each command when
this setting is in effect.

This also removes a "//" comment and changes scoped_command_stats to
use DISABLE_COPY_AND_ASSIGN; two minor things I noticed while working
on the patch.

Tested on x86-64 Fedora 29.

gdb/ChangeLog
2019-06-06  Tom Tromey  <tromey@adacore.com>

	* maint.h (class scoped_command_stats): Use
	DISABLE_COPY_AND_ASSIGN.
	<print_time>: New method.
	* maint.c (scoped_command_stats, ~scoped_command_stats): Call
	print_time.
	(scoped_command_stats::print_time): New method.

gdb/testsuite/ChangeLog
2019-06-06  Tom Tromey  <tromey@adacore.com>

	* gdb.base/maint.exp: Expect command started/finished output.

1 files changed, 25 insertions, 0 deletions

diff --git a/gdb/maint.c b/gdb/maint.c
index 328d602..aaabb35 100644
--- a/gdb/maint.c
+++ b/gdb/maint.c
@@ -794,6 +794,8 @@ scoped_command_stats::~scoped_command_stats ()
 
   if (m_time_enabled && per_command_time)
     {
+      print_time (_("command finished"));
+
       using namespace std::chrono;
 
       run_time_clock::duration cmd_time
@@ -867,6 +869,9 @@ scoped_command_stats::scoped_command_stats (bool msg_type)
       m_start_cpu_time = run_time_clock::now ();
       m_start_wall_time = steady_clock::now ();
       m_time_enabled = 1;
+
+      if (per_command_time)
+	print_time (_("command started"));
     }
   else
     m_time_enabled = 0;
@@ -888,6 +893,26 @@ scoped_command_stats::scoped_command_stats (bool msg_type)
   reset_prompt_for_continue_wait_time ();
 }
 
+/* See maint.h.  */
+
+void
+scoped_command_stats::print_time (const char *msg)
+{
+  using namespace std::chrono;
+
+  auto now = system_clock::now ();
+  auto ticks = now.time_since_epoch ().count () / (1000 * 1000);
+  auto millis = ticks % 1000;
+
+  std::time_t as_time = system_clock::to_time_t (now);
+  struct tm *tm = localtime (&as_time);
+
+  char out[100];
+  strftime (out, sizeof (out), "%F %H:%M:%S", tm);
+
+  printf_unfiltered ("%s.%03d - %s\n", out, (int) millis, msg);
+}
+
 /* Handle unknown "mt set per-command" arguments.
    In this case have "mt set per-command on|off" affect every setting.  */