re PR other/31349 (gcc -v --help returns no options for C, C++)

        PR other/31349
        * opts.c (undocumented_msg): Leave blank unless checking is
        enabled.
        (handle_options): Fix indentation.
        (print_filtered_help): If no language-specific options were
        displayed tell the user how to list all the options supported by
        the language's front-end.
        (print_specific_help): Fix indentation and remove duplicate line.
        (common_handle_option): Handle the -v option.
        For --help enable the display of undocumented options if the -v
        switch has been included on the command line.
        For --help= check for overlaps in the arguments between the option
        classes and the language names and issue a warning when they
        cannot be disambiguated.
        * c.opt (v): Pass on to the common option handler.

From-SVN: r132427

gcc/ChangeLog

+2008-02-19  Nick Clifton  <nickc@redhat.com>
+
+	PR other/31349
+	* opts.c (undocumented_msg): Leave blank unless checking is
+	enabled.
+	(handle_options): Fix indentation.
+	(print_filtered_help): If no language-specific options were
+	displayed tell the user how to list all the options supported by
+	the language's front-end.
+	(print_specific_help): Fix indentation and remove duplicate line.
+	(common_handle_option): Handle the -v option.
+	For --help enable the display of undocumented options if the -v
+	switch has been included on the command line.
+	For --help= check for overlaps in the arguments between the option
+	classes and the language names and issue a warning when they
+	cannot be disambiguated.
+	* c.opt (v): Pass on to the common option handler.
+
 2008-02-19  Revital Eres  <eres@il.ibm.com> 
 
 	* modulo-sched.c (sms_schedule): Change dump message when

gcc/c.opt

@@ -978,7 +978,7 @@ C ObjC C++ ObjC++
 Do not predefine system-specific and GCC-specific macros
 
 v
-C ObjC C++ ObjC++
+Common C ObjC C++ ObjC++
 Enable verbose output
 
 w

gcc/opts.c

@@ -337,7 +337,11 @@ bool no_unit_at_a_time_default;
 struct visibility_flags visibility_options;
 
 /* What to print when a switch has no documentation.  */
+#ifdef ENABLE_CHECKING
 static const char undocumented_msg[] = N_("This switch lacks documentation");
+#else
+static const char undocumented_msg[] = "";
+#endif
 
 /* Used for bookkeeping on whether user set these flags so
    -fprofile-use/-fprofile-generate does not use them.  */
@@ -703,7 +707,7 @@ handle_options (unsigned int argc, const char **argv, unsigned int lang_mask)
 	{
 	  if (main_input_filename == NULL)
 	    {
-	    main_input_filename = opt;
+	      main_input_filename = opt;
 	      main_input_baselength
 		= base_of_path (main_input_filename, &main_input_basename);
 	    }
@@ -1169,7 +1173,24 @@ print_filtered_help (unsigned int include_flags,
     }
 
   if (! found)
-    printf (_(" No options with the desired characteristics were found\n"));
+    {
+      unsigned int langs = include_flags & CL_LANG_ALL;
+
+      if (langs == 0)
+	printf (_(" No options with the desired characteristics were found\n"));
+      else
+	{
+	  unsigned int i;
+
+	  /* PR 31349: Tell the user how to see all of the
+	     options supported by a specific front end.  */
+	  for (i = 0; (1U << i) < CL_LANG_ALL; i ++)
+	    if ((1U << i) & langs)
+	      printf (_(" None found.  Use --help=%s to show *all* the options supported by the %s front-end\n"),
+		      lang_names[i], lang_names[i]);
+	}
+	
+    }
   else if (! displayed)
     printf (_(" All options with the desired characteristics have already been displayed\n"));
 
@@ -1243,13 +1264,10 @@ print_specific_help (unsigned int include_flags,
 	  if (i >= cl_lang_count)
 	    break;
 	  if ((exclude_flags & ((1U << cl_lang_count) - 1)) != 0)
-	    {
-	      description = _("The following options are specific to the language ");
-	      descrip_extra = lang_names [i];
-	    }
+	    description = _("The following options are specific to the just the language ");
 	  else
 	    description = _("The following options are supported by the language ");
-	    descrip_extra = lang_names [i];
+	  descrip_extra = lang_names [i];
 	  break;
 	}
     }
@@ -1289,6 +1307,7 @@ static int
 common_handle_option (size_t scode, const char *arg, int value,
 		      unsigned int lang_mask)
 {
+  static bool verbose = false;
   enum opt_code code = (enum opt_code) scode;
 
   switch (code)
@@ -1297,6 +1316,10 @@ common_handle_option (size_t scode, const char *arg, int value,
       handle_param (arg);
       break;
 
+    case OPT_v:
+      verbose = true;
+      break;
+
     case OPT_fhelp:
     case OPT__help:
       {
@@ -1304,7 +1327,7 @@ common_handle_option (size_t scode, const char *arg, int value,
 	unsigned int undoc_mask;
 	unsigned int i;
 
-	undoc_mask = extra_warnings ? 0 : CL_UNDOCUMENTED;
+	undoc_mask = (verbose | extra_warnings) ? 0 : CL_UNDOCUMENTED;
 	/* First display any single language specific options.  */
 	for (i = 0; i < cl_lang_count; i++)
 	  print_specific_help
@@ -1366,6 +1389,7 @@ common_handle_option (size_t scode, const char *arg, int value,
 	    };
 	    unsigned int * pflags;
 	    char * comma;
+	    unsigned int lang_flag, specific_flag;
 	    unsigned int len;
 	    unsigned int i;
 
@@ -1383,28 +1407,52 @@ common_handle_option (size_t scode, const char *arg, int value,
 	    else
 	      len = comma - a;
 
-	    for (i = 0; specifics[i].string != NULL; i++)
+	    /* Check to see if the string matches an option class name.  */
+	    for (i = 0, specific_flag = 0; specifics[i].string != NULL; i++)
 	      if (strncasecmp (a, specifics[i].string, len) == 0)
 		{
-		  * pflags |= specifics[i].flag;
+		  specific_flag = specifics[i].flag;
+		  break;
+		}
+	    
+	    /* Check to see if the string matches a language name.
+	       Note - we rely upon the alpha-sorted nature of the entries in
+	       the lang_names array, specifically that shorter names appear
+	       before their longer variants.  (ie C before C++).  That way
+	       when we are attempting to match --help=c for example we will
+	       match with C first and not C++.  */
+	    for (i = 0, lang_flag = 0; i < cl_lang_count; i++)
+	      if (strncasecmp (a, lang_names[i], len) == 0)
+		{
+		  lang_flag = 1U << i;
 		  break;
 		}
 
-	    if (specifics[i].string == NULL)
+	    if (specific_flag != 0)
 	      {
-		/* Check to see if the string matches a language name.  */
-		for (i = 0; i < cl_lang_count; i++)
-		  if (strncasecmp (a, lang_names[i], len) == 0)
-		    {
-		      * pflags |= 1U << i;
-		      break;
-		    }
-
-		if (i == cl_lang_count)
-		  fnotice (stderr,
-			   "warning: unrecognized argument to --help= switch: %.*s\n",
-			   len, a);
+		if (lang_flag == 0)
+		  * pflags |= specific_flag;
+		else
+		  {
+		    /* The option's argument matches both the start of a
+		       language name and the start of an option class name.
+		       We have a special case for when the user has
+		       specified "--help=c", but otherwise we have to issue
+		       a warning.  */
+		    if (strncasecmp (a, "c", len) == 0)
+		      * pflags |= lang_flag;
+		    else
+		      fnotice (stderr,
+			       "warning: --help argument %.*s is ambiguous, please be more specific\n",
+			       len, a);
+		  }
 	      }
+	    else if (lang_flag != 0)
+	      * pflags |= lang_flag;
+	    else
+	      fnotice (stderr,
+		       "warning: unrecognized argument to --help= option: %.*s\n",
+		       len, a);
 
 	    if (comma == NULL)
 	      break;