Refactor string_to_event_location for legacy linespec support.

This patch refactors string_to_event_location, breaking it into two
separate functions:

1) string_to_event_location_basic
A "basic" string parser that implements support for "legacy" linespecs
(linespec, address, and probe locations).  This function is intended to
be used by any UI wishing/needing to support this legacy behavior.

2) string_to_event_location
This is now intended as a CLI-only function which adds explicit location
parsing in a CLI-appropriate manner (in the form of traditional option/value
pairs).

Together these patches serve to simplify string-to-event location parsing
for all existing non-CLI interfaces (MI, guile, and python).

gdb/ChangeLog

	* location.c (string_to_explicit_location): Note that "-p" is
	reserved for probe locations and return NULL for any input
	that starts with that.
	(string_to_event_location): Move "legacy" linespec code to ...
	(string_to_event_location_basic): ... here.
	* location.h (string_to_event_location): Update comment.
	(string_to_event_location_basic): New function.

gdb/ChangeLog

@@ -1,3 +1,13 @@
+2016-02-09  Keith Seitz  <keiths@redhat.com>
+
+	* location.c (string_to_explicit_location): Note that "-p" is
+	reserved for probe locations and return NULL for any input
+	that starts with that.
+	(string_to_event_location): Move "legacy" linespec code to ...
+	(string_to_event_location_basic): ... here.
+	* location.h (string_to_event_location): Update comment.
+	(string_to_event_location_basic): New function.
+
 2016-02-09  Simon Marchi  <simon.marchi@ericsson.com>
 
 	* configure.ac: Use AC_CONFIG_FILES instead of passing arguments

gdb/location.c

@@ -522,11 +522,13 @@ string_to_explicit_location (const char **argp,
   struct event_location *location;
 
   /* It is assumed that input beginning with '-' and a non-digit
-     character is an explicit location.  */
+     character is an explicit location.  "-p" is reserved, though,
+     for probe locations.  */
   if (argp == NULL
       || *argp == '\0'
       || *argp[0] != '-'
-      || !isalpha ((*argp)[1]))
+      || !isalpha ((*argp)[1])
+      || ((*argp)[0] == '-' && (*argp)[1] == 'p'))
     return NULL;
 
   location = new_explicit_location (NULL);
@@ -633,53 +635,66 @@ string_to_explicit_location (const char **argp,
 
 /* See description in location.h.  */
 
+struct event_location *
+string_to_event_location_basic (char **stringp,
+				const struct language_defn *language)
+{
+  struct event_location *location;
+  const char *arg, *orig, *cs;
+
+  /* Try the input as a probe spec.  */
+  cs = *stringp;
+  if (cs != NULL && probe_linespec_to_ops (&cs) != NULL)
+    {
+      location = new_probe_location (*stringp);
+      *stringp += strlen (*stringp);
+    }
+  else
+    {
+      /* Try an address location.  */
+      if (*stringp != NULL && **stringp == '*')
+	{
+	  const char *arg, *orig;
+	  CORE_ADDR addr;
+
+	  orig = arg = *stringp;
+	  addr = linespec_expression_to_pc (&arg);
+	  location = new_address_location (addr, orig, arg - orig);
+	  *stringp += arg - orig;
+	}
+      else
+	{
+	  /* Everything else is a linespec.  */
+	  location = new_linespec_location (stringp);
+	}
+    }
+
+  return location;
+}
+
+/* See description in location.h.  */
+
 struct event_location *
 string_to_event_location (char **stringp,
 			  const struct language_defn *language)
 {
   struct event_location *location;
+  const char *arg, *orig;
 
-  /* First, check if the string is an address location.  */
+  /* Try an explicit location.  */
-  if (*stringp != NULL && **stringp == '*')
+  orig = arg = *stringp;
+  location = string_to_explicit_location (&arg, language, 0);
+  if (location != NULL)
     {
-      const char *arg, *orig;
+      /* It was a valid explicit location.  Advance STRINGP to
-      CORE_ADDR addr;
+	 the end of input.  */
-
-      orig = arg = *stringp;
-      addr = linespec_expression_to_pc (&arg);
-      location = new_address_location (addr, orig, arg - orig);
       *stringp += arg - orig;
     }
   else
     {
-      const char *cs;
+      /* Everything else is a "basic" linespec, address, or probe
-
+	 location.  */
-      /* Next, try the input as a probe spec.  */
+      location = string_to_event_location_basic (stringp, language);
-      cs = *stringp;
-      if (cs != NULL && probe_linespec_to_ops (&cs) != NULL)
-	{
-	  location = new_probe_location (*stringp);
-	  *stringp += strlen (*stringp);
-	}
-      else
-	{
-	  const char *arg, *orig;
-
-	  /* Next, try an explicit location.  */
-	  orig = arg = *stringp;
-	  location = string_to_explicit_location (&arg, language, 0);
-	  if (location != NULL)
-	    {
-	      /* It was a valid explicit location.  Advance STRINGP to
-		 the end of input.  */
-	      *stringp += arg - orig;
-	    }
-	  else
-	    {
-	      /* Everything else is a linespec.  */
-	      location = new_linespec_location (stringp);
-	    }
-	}
     }
 
   return location;

gdb/location.h

@@ -207,12 +207,24 @@ extern struct event_location *
    but invalid, input, e.g., if it is called with missing argument parameters
    or invalid options.
 
-   The return result must be freed with delete_event_location.  */
+   The return result must be freed with delete_event_location.
+
+   This function is intended to be used by CLI commands and will parse
+   explicit locations in a CLI-centric way.  Other interfaces should use
+   string_to_event_location_basic if they want to maintain support for
+   legacy specifications of probe, address, and linespec locations.  */
 
 extern struct event_location *
   string_to_event_location (char **argp,
 			    const struct language_defn *langauge);
 
+/* Like string_to_event_location, but does not attempt to parse explicit
+   locations.  */
+
+extern struct event_location *
+  string_to_event_location_basic (char **argp,
+				  const struct language_defn *language);
+
 /* Attempt to convert the input string in *ARGP into an explicit location.
    ARGP is advanced past any processed input.  Returns an event_location
    (malloc'd) if an explicit location was successfully found in *ARGP,