[RFC/RFA PATCH] Fix completer.c FIXME, and invalid pointer to pointer conversion.

[Pedro Alves <palves at redhat dot com>]

As mentioned in the previous patch, I grepped for "\*\*) &" and found one
hit in completer.c.

I was about to post a patch that simply made
current_demangling_style_string const, and cast away constness at the
xfree site.  However, looking deeper, it seem to be there's a lot of
dead code in the file.

First, all external callers of set_demangling_style are found in the
stabs reader, commented out for over 12 years:

  http://sourceware.org/ml/gdb-patches/2000-12/msg00214.html

I don't think it's likely we'll ever make the older mangling schemes
work for stabs.  If we do, we can rediscuss the approach then.

Then, set_demangling_command has special handling for unknown
demangling styles, but "set demangle-style" is an enum command, and
with those, the user can only specify a known enumeration value, by
design:

  (gdb) set demangle-style gangnam-style
  Undefined item: "gangnam-style".


This patch removes all that dead code, then makes
current_demangling_style_string point to an element of
demangling_style_names, as the FIXME suggests, and then makes
current_demangling_style_string, removing the need for the 'const char
**' cast.

gdb/
2013-03-13  Pedro Alves  <palves@redhat.com>

	* dbxread.c (read_ofile_symtab, process_one_symbol): Remove
	commented out code.
	* demangle.c (current_demangling_style_string): Make it const.
	(set_demangling_command): Assert the demangling style is known.
	Remove all handling of unknown styles.  Set
	'current_demangling_style_string' to an element of the
	demangling_style_names array.
	(set_demangling_style): Delete.
	(_initialize_demangler): Set current_demangling_style_string to the
	element of the demangling_style_names array that corresponds to
	the default demangling style.  Remove FIXME note.  Don't call
	set_demangling_style.
	* gdb-demangle.h (set_demangling_style): Remove declaration.
---
 gdb/dbxread.c      |   33 ---------------------
 gdb/demangle.c     |   82 ++++++++++++----------------------------------------
 gdb/gdb-demangle.h |    3 --
 3 files changed, 19 insertions(+), 99 deletions(-)

diff --git a/gdb/dbxread.c b/gdb/dbxread.c
index 09b46a0..435c518 100644
--- a/gdb/dbxread.c
+++ b/gdb/dbxread.c
@@ -2580,21 +2580,6 @@ read_ofile_symtab (struct objfile *objfile, struct partial_symtab *pst)
 	  if (strncmp (tempstring, "__gnu_compiled", 14) == 0)
 	    processing_gcc_compilation = 2;
 	}
-
-      /* Try to select a C++ demangling based on the compilation unit
-         producer.  */
-
-#if 0
-      /* For now, stay with AUTO_DEMANGLING for g++ output, as we don't
-	 know whether it will use the old style or v3 mangling.  */
-      if (processing_gcc_compilation)
-	{
-	  if (AUTO_DEMANGLING)
-	    {
-	      set_demangling_style (GNU_DEMANGLING_STYLE_STRING);
-	    }
-	}
-#endif
     }
   else
     {
@@ -2660,15 +2645,6 @@ read_ofile_symtab (struct objfile *objfile, struct partial_symtab *pst)
 	    processing_gcc_compilation = 1;
 	  else if (strcmp (namestring, GCC2_COMPILED_FLAG_SYMBOL) == 0)
 	    processing_gcc_compilation = 2;
-
-#if 0
-	  /* For now, stay with AUTO_DEMANGLING for g++ output, as we don't
-	     know whether it will use the old style or v3 mangling.  */
-	  if (AUTO_DEMANGLING)
-	    {
-	      set_demangling_style (GNU_DEMANGLING_STYLE_STRING);
-	    }
-#endif
 	}
       else if (type & N_EXT || type == (unsigned char) N_TEXT
 	       || type == (unsigned char) N_NBTEXT)
@@ -3270,15 +3246,6 @@ process_one_symbol (int type, int desc, CORE_ADDR valu, char *name,
 	  if (strcmp (name, GCC2_COMPILED_FLAG_SYMBOL) == 0)
 	    {
 	      processing_gcc_compilation = 2;
-#if 0				/* Works, but is experimental.  -fnf */
-	      /* For now, stay with AUTO_DEMANGLING for g++ output, as
-		 we don't know whether it will use the old style or v3
-		 mangling.  */
-	      if (AUTO_DEMANGLING)
-		{
-		  set_demangling_style (GNU_DEMANGLING_STYLE_STRING);
-		}
-#endif
 	    }
 	  else
 	    n_opt_found = 1;
diff --git a/gdb/demangle.c b/gdb/demangle.c
index 1cbfe99..415d891 100644
--- a/gdb/demangle.c
+++ b/gdb/demangle.c
@@ -72,7 +72,7 @@ show_asm_demangle (struct ui_file *file, int from_tty,
    "set demangle-style" command, printed as part of the output by the
    "show demangle-style" command.  */
 
-static char *current_demangling_style_string;
+static const char *current_demangling_style_string;
 
 /* The array of names of the known demanglyng styles.  Generated by
    _initialize_demangler from libiberty_demanglers[] array.  */
@@ -106,13 +106,14 @@ static void
 set_demangling_command (char *ignore, int from_tty, struct cmd_list_element *c)
 {
   const struct demangler_engine *dem;
+  int i;
 
   /*  First just try to match whatever style name the user supplied with
      one of the known ones.  Don't bother special casing for an empty
      name, we just treat it as any other style name that doesn't match.
      If we match, update the current demangling style enum.  */
 
-  for (dem = libiberty_demanglers; 
+  for (dem = libiberty_demanglers, i = 0;
        dem->demangling_style != unknown_demangling; 
        dem++)
     {
@@ -120,60 +121,15 @@ set_demangling_command (char *ignore, int from_tty, struct cmd_list_element *c)
 		  dem->demangling_style_name) == 0)
 	{
 	  current_demangling_style = dem->demangling_style;
+	  current_demangling_style_string = demangling_style_names[i];
 	  break;
 	}
+      i++;
     }
 
-  /* Check to see if we found a match.  If not, gripe about any non-empty
-     style name and supply a list of valid ones.  FIXME: This should
-     probably be done with some sort of completion and with help.  */
-
-  if (dem->demangling_style == unknown_demangling)
-    {
-      if (*current_demangling_style_string != '\0')
-	{
-	  printf_unfiltered (_("Unknown demangling style `%s'.\n"),
-			     current_demangling_style_string);
-	}
-      printf_unfiltered (_("The currently understood settings are:\n\n"));
-      for (dem = libiberty_demanglers; 
-	   dem->demangling_style != unknown_demangling; 
-	   dem++)
-	{
-	  printf_unfiltered ("%-10s %s\n", dem->demangling_style_name,
-			     dem->demangling_style_doc);
-	  if (dem->demangling_style == current_demangling_style)
-	    {
-	      xfree (current_demangling_style_string);
-	      current_demangling_style_string =
-		xstrdup (dem->demangling_style_name);
-	    }
-	}
-      if (current_demangling_style == unknown_demangling)
-	{
-	  /* This can happen during initialization if gdb is compiled with
-	     a DEMANGLING_STYLE value that is unknown, so pick the first
-	     one as the default.  */
-	  current_demangling_style = libiberty_demanglers[0].demangling_style;
-	  current_demangling_style_string =
-	    xstrdup (libiberty_demanglers[0].demangling_style_name);
-	  warning (_("`%s' style demangling chosen as the default."),
-		   current_demangling_style_string);
-	}
-    }
-}
-
-/* See documentation in gdb-demangle.h.  */
-
-void
-set_demangling_style (char *style)
-{
-  if (current_demangling_style_string != NULL)
-    {
-      xfree (current_demangling_style_string);
-    }
-  current_demangling_style_string = xstrdup (style);
-  set_demangling_command ((char *) NULL, 0, (struct cmd_list_element *) NULL);
+  /* We should have found a match, given we only add known styles to
+     the enumeration list.  */
+  gdb_assert (dem->demangling_style != unknown_demangling);
 }
 
 /* G++ uses a special character to indicate certain internal names.  Which
@@ -204,7 +160,8 @@ _initialize_demangler (void)
 {
   int i, ndems;
 
-  /* Fill the demangling_style_names[] array.  */
+  /* Fill the demangling_style_names[] array, and set the default
+     demangling style chosen at compilation time.  */
   for (ndems = 0;
        libiberty_demanglers[ndems].demangling_style != unknown_demangling; 
        ndems++)
@@ -213,8 +170,14 @@ _initialize_demangler (void)
   for (i = 0;
        libiberty_demanglers[i].demangling_style != unknown_demangling; 
        i++)
-    demangling_style_names[i] =
-      xstrdup (libiberty_demanglers[i].demangling_style_name);
+    {
+      demangling_style_names[i]
+	= xstrdup (libiberty_demanglers[i].demangling_style_name);
+
+      if (current_demangling_style_string == NULL
+	  && strcmp (DEFAULT_DEMANGLING_STYLE, demangling_style_names[i]) == 0)
+	current_demangling_style_string = demangling_style_names[i];
+    }
 
   add_setshow_boolean_cmd ("demangle", class_support, &demangle, _("\
 Set demangling of encoded C++/ObjC names when displaying symbols."), _("\
@@ -230,20 +193,13 @@ Show demangling of C++/ObjC names in disassembly listings."), NULL,
 			   show_asm_demangle,
 			   &setprintlist, &showprintlist);
 
-  /* FIXME: cagney/2005-02-20: The code implementing this variable are
-     malloc-ing and free-ing current_demangling_style_string when it
-     should instead just point to an element of
-     demangling_style_names.  */
   add_setshow_enum_cmd ("demangle-style", class_support,
 			demangling_style_names,
-			(const char **) &current_demangling_style_string, _("\
+			&current_demangling_style_string, _("\
 Set the current C++ demangling style."), _("\
 Show the current C++ demangling style."), _("\
 Use `set demangle-style' without arguments for a list of demangling styles."),
 			set_demangling_command,
 			show_demangling_style_names,
 			&setlist, &showlist);
-
-  /* Set the default demangling style chosen at compilation time.  */
-  set_demangling_style (DEFAULT_DEMANGLING_STYLE);
 }
diff --git a/gdb/gdb-demangle.h b/gdb/gdb-demangle.h
index 1e91414..cd4e27c 100644
--- a/gdb/gdb-demangle.h
+++ b/gdb/gdb-demangle.h
@@ -28,9 +28,6 @@ extern int demangle;
    DEMANGLE is zero, names are printed raw, i.e. DEMANGLE controls.  */
 extern int asm_demangle;
 
-/* Fake a "set demangle-style" command.  */
-extern void set_demangling_style (char *);
-
 /* Check if a character is one of the commonly used C++ marker characters.  */
 extern int is_cplus_marker (int);