Add helper functions parse_flags and parse_flags_qcs

Add helper functions parse_flags and parse_flags_qcs.
parse_flags helper function allows to look for a set of flags at
the start of a string.
A flag must be given individually.

parse_flags_qcs is a specialised helper function to handle
the flags -q, -c and -s, that are used in the new command 'frame apply'
and in the command 'thread apply.

Modify number_or_range_parser::get_number to differentiate a
- followed by digits from a - followed by an alpha (i.e. a flag or an option).
That is needed for the addition of the [FLAG]... arguments to
thread apply ID... [FLAG]... COMMAND

Remove bool number_or_range_parser::m_finished, rather
implement the 'finished' logic inside number_or_range_parser::finished.
The new logic properly detects the end of parsing even if not at
end of the string. This ensures that number_or_range_parser::cur_tok
really points past the last parsed token when parsing is finished.
Before, it was always pointing at the end of the string.
As parsing now is finished directly when not positioned on a number,
number_is_in_list must do an error check before the loop getting all
numbers.

The error message for 'thread apply -$unknownconvvar p 1'
is now the more clear:
  Convenience variable must have integer value.
  Invalid thread ID: -$unknownconvvar p 1
instead of previously:
  negative value

gdb/ChangeLog
2018-07-12  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* cli-utils.c (number_or_range_parser::get_number): Only handle
	numbers or convenience var as numbers.
	(parse_flags): New function.
	(parse_flags_qcs): New function.
	(number_or_range_parser::finished): Ensure parsing end is detected
	before end of string.
	* cli-utils.h (parse_flags): New function.
	(parse_flags_qcs): New function.
	(number_or_range_parser): Remove m_finished bool.
	(number_or_range_parser::skip_range): Set m_in_range to false.

gdb/testsuite/ChangeLog
2018-07-12  Philippe Waroquiers  <philippe.waroquiers@skynet.be>

	* gdb.base/skip.exp: Update expected error message.

gdb/cli/cli-utils.c

@@ -137,7 +137,6 @@ number_or_range_parser::number_or_range_parser (const char *string)
 void
 number_or_range_parser::init (const char *string)
 {
-  m_finished = false;
   m_cur_tok = string;
   m_last_retval = 0;
   m_end_value = 0;
@@ -169,7 +168,10 @@ number_or_range_parser::get_number ()
       /* Default case: state->m_cur_tok is pointing either to a solo
 	 number, or to the first number of a range.  */
       m_last_retval = get_number_trailer (&m_cur_tok, '-');
-      if (*m_cur_tok == '-')
+      /* If get_number_trailer has found a -, it might be the start
+	 of a command option.  So, do not parse a range if the - is
+	 followed by an alpha.  */
+      if (*m_cur_tok == '-' && !isalpha (*(m_cur_tok + 1)))
 	{
 	  const char **temp;
 
@@ -196,8 +198,17 @@ number_or_range_parser::get_number ()
 	}
     }
   else
-    error (_("negative value"));
-  m_finished = *m_cur_tok == '\0';
+    {
+      if (isdigit (*(m_cur_tok + 1)))
+	error (_("negative value"));
+      if (*(m_cur_tok + 1) == '$')
+	{
+	  /* Convenience variable.  */
+	  m_last_retval = ::get_number (&m_cur_tok);
+	  if (m_last_retval < 0)
+	    error (_("negative value"));
+	}
+    }
   return m_last_retval;
 }
 
@@ -215,6 +226,21 @@ number_or_range_parser::setup_range (int start_value, int end_value,
   m_end_value = end_value;
 }
 
+/* See documentation in cli-utils.h.  */
+
+bool
+number_or_range_parser::finished () const
+{
+  /* Parsing is finished when at end of string or null string,
+     or we are not in a range and not in front of an integer, negative
+     integer, convenience var or negative convenience var.  */
+  return (m_cur_tok == NULL || *m_cur_tok == '\0'
+	  || (!m_in_range
+	      && !(isdigit (*m_cur_tok) || *m_cur_tok == '$')
+	      && !(*m_cur_tok == '-'
+		   && (isdigit (m_cur_tok[1]) || m_cur_tok[1] == '$'))));
+}
+
 /* Accept a number and a string-form list of numbers such as is 
    accepted by get_number_or_range.  Return TRUE if the number is
    in the list.
@@ -230,12 +256,15 @@ number_is_in_list (const char *list, int number)
     return 1;
 
   number_or_range_parser parser (list);
+
+  if (parser.finished ())
+    error (_("Arguments must be numbers or '$' variables."));
   while (!parser.finished ())
     {
       int gotnum = parser.get_number ();
 
       if (gotnum == 0)
-	error (_("Args must be numbers or '$' variables."));
+	error (_("Arguments must be numbers or '$' variables."));
       if (gotnum == number)
 	return 1;
     }
@@ -304,3 +333,60 @@ check_for_argument (const char **str, const char *arg, int arg_len)
     }
   return 0;
 }
+
+/* See documentation in cli-utils.h.  */
+
+int
+parse_flags (const char **str, const char *flags)
+{
+  const char *p = skip_spaces (*str);
+
+  if (p[0] == '-'
+      && isalpha (p[1])
+      && (p[2] == '\0' || isspace (p[2])))
+    {
+      const char pf = p[1];
+      const char *f = flags;
+
+      while (*f != '\0')
+	{
+	  if (*f == pf)
+	    {
+	      *str = skip_spaces (p + 2);
+	      return f - flags + 1;
+	    }
+	  f++;
+	}
+    }
+
+  return 0;
+}
+
+/* See documentation in cli-utils.h.  */
+
+bool
+parse_flags_qcs (const char *which_command, const char **str,
+		 qcs_flags *flags)
+{
+  switch (parse_flags (str, "qcs"))
+    {
+    case 0:
+      return false;
+    case 1:
+      flags->quiet = true;
+      break;
+    case 2:
+      flags->cont = true;
+      break;
+    case 3:
+      flags->silent = true;
+      break;
+    default:
+      gdb_assert_not_reached ("int qcs flag out of bound");
+    }
+
+  if (flags->cont && flags->silent)
+    error (_("%s: -c and -s are mutually exclusive"), which_command);
+
+  return true;
+}