Make language_def O(1)

Profiling GDB with the rest of series applied, I saw calls to
language_def showing up high in some runs.  The problem is that
language_def is O(N) currently, since walk the languages vector each
time to find the matching language_defn.

IMO, the add_language mechanism is pointless, because "enum language"
implies the core of GDB needs to know about all languages anyway.  So
simply make the languages vector array be an array where each
element's index is the corresponding enum language enumerator.  Note
that "local_language_defn" is gone along the way.  It's just a copy of
"auto", so the new code simply maps one to the other.  One fewer place
to update when we need to change the language vector...

Also, a while ago the output of "set language" was made out of order
as side effect of some other change.  While I was at it, I made them
sorted again.

gdb/ChangeLog:
2017-07-20  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (ada_language_defn): Make extern.
	(_initialize_ada_language): Remove add_language call.
	* c-lang.c (c_language_defn, cplus_language_defn)
	(asm_language_defn, minimal_language_defn): Make extern.
	(_initialize_c_language): Delete.
	* completer.c (compare_cstrings): Delete, moved to utils.h.
	* d-lang.c (d_language_defn): Make extern.
	(_initialize_d_language): Remove add_language calls.
	* defs.h (enum language): Add comment.
	* f-lang.c (f_language_defn): Make extern.
	(_initialize_f_language): Remove add_language call.
	* go-lang.c (go_language_defn): Make extern.
	(_initialize_go_language): Remove add_language call.
	* language.c: Include <algorithm>.
	(languages): Redefine as const array.
	(languages_size, languages_allocsize, DEFAULT_ALLOCSIZE): Delete.
	(set_language_command): Handle "local".  Use for-range loop.
	(set_language): Remove loop.
	(language_enum): Rewrite.
	(language_def, language_str): Remove loops.
	(add_language): Delete.
	(add_set_language_command): New, based on add_languages.
	(skip_language_trampoline): Adjust.
	(local_language_defn): Delete.
	(language_gdbarch_post_init): Adjust.
	(_initialize_language): Remove add_language calls.  Call
	add_set_language_command.
	* language.h (add_language): Delete.
	(auto_language_defn)
	(unknown_language_defn, minimal_language_defn, ada_language_defn)
	(asm_language_defn, c_language_defn, cplus_language_defn)
	(d_language_defn, f_language_defn, go_language_defn)
	(m2_language_defn, objc_language_defn, opencl_language_defn)
	(pascal_language_defn, rust_language_defn): Declare.
	* m2-lang.c (m2_language_defn): Make extern.
	(_initialize_m2_language): Remove add_language call.
	* objc-lang.c (objc_language_defn): Make extern.
	(_initialize_objc_language): Remove add_language call.
	* opencl-lang.c (opencl_language_defn): Make extern.
	(_initialize_opencl_language): Remove add_language call.
	* p-lang.c (pascal_language_defn): Make extern.
	(_initialize_pascal_language): Delete.
	* rust-lang.c (rust_language_defn): Make extern.
	(_initialize_rust_language): Delete.
	* utils.h (compare_cstrings): New static inline function.

gdb/testsuite/ChangeLog:
2017-07-20  Pedro Alves  <palves@redhat.com>

	* gdb.base/default.exp (set language): Adjust expected output.

1 files changed, 89 insertions, 159 deletions

diff --git a/gdb/language.c b/gdb/language.c
index d30f4f0..073039e 100644
--- a/gdb/language.c
+++ b/gdb/language.c
@@ -44,6 +44,7 @@
 #include "cp-support.h"
 #include "frame.h"
 #include "c-lang.h"
+#include <algorithm>
 
 extern void _initialize_language (void);
 
@@ -91,12 +92,26 @@ enum language_mode language_mode = language_mode_auto;
 
 const struct language_defn *expected_language;
 
-/* The list of supported languages.  The list itself is malloc'd.  */
-
-static const struct language_defn **languages;
-static unsigned languages_size;
-static unsigned languages_allocsize;
-#define	DEFAULT_ALLOCSIZE 4
+/* The list of supported languages.  Keep this in the same order as
+   the 'enum language' values.  */
+
+static const struct language_defn *languages[] = {
+  &unknown_language_defn,
+  &auto_language_defn,
+  &c_language_defn,
+  &objc_language_defn,
+  &cplus_language_defn,
+  &d_language_defn,
+  &go_language_defn,
+  &f_language_defn,
+  &m2_language_defn,
+  &asm_language_defn,
+  &pascal_language_defn,
+  &opencl_language_defn,
+  &rust_language_defn,
+  &minimal_language_defn,
+  &ada_language_defn,
+};
 
 /* The current values of the "set language/type/range" enum
    commands.  */
@@ -148,16 +163,19 @@ show_language_command (struct ui_file *file, int from_tty,
 static void
 set_language_command (char *ignore, int from_tty, struct cmd_list_element *c)
 {
-  int i;
   enum language flang = language_unknown;
 
+  /* "local" is a synonym of "auto".  */
+  if (strcmp (language, "local") == 0)
+    language = "auto";
+
   /* Search the list of languages for a match.  */
-  for (i = 0; i < languages_size; i++)
+  for (const auto &lang : languages)
     {
-      if (strcmp (languages[i]->la_name, language) == 0)
+      if (strcmp (lang->la_name, language) == 0)
 	{
 	  /* Found it!  Go into manual mode, and use this language.  */
-	  if (languages[i]->la_language == language_auto)
+	  if (lang->la_language == language_auto)
 	    {
 	      /* Enter auto mode.  Set to the current frame's language, if
                  known, or fallback to the initial language.  */
@@ -186,7 +204,7 @@ set_language_command (char *ignore, int from_tty, struct cmd_list_element *c)
 	    {
 	      /* Enter manual mode.  Set the specified language.  */
 	      language_mode = language_mode_manual;
-	      current_language = languages[i];
+	      current_language = lang;
 	      set_range_case ();
 	      expected_language = current_language;
 	      return;
@@ -364,21 +382,11 @@ set_range_case (void)
 enum language
 set_language (enum language lang)
 {
-  int i;
   enum language prev_language;
 
   prev_language = current_language->la_language;
-
-  for (i = 0; i < languages_size; i++)
-    {
-      if (languages[i]->la_language == lang)
-	{
-	  current_language = languages[i];
-	  set_range_case ();
-	  break;
-	}
-    }
-
+  current_language = languages[lang];
+  set_range_case ();
   return prev_language;
 }
 
@@ -474,11 +482,12 @@ range_error (const char *string,...)
 enum language
 language_enum (char *str)
 {
-  int i;
+  for (const auto &lang : languages)
+    if (strcmp (lang->la_name, str) == 0)
+      return lang->la_language;
 
-  for (i = 0; i < languages_size; i++)
-    if (strcmp (languages[i]->la_name, str) == 0)
-      return languages[i]->la_language;
+  if (strcmp (str, "local") == 0)
+    return language_auto;
 
   return language_unknown;
 }
@@ -488,32 +497,15 @@ language_enum (char *str)
 const struct language_defn *
 language_def (enum language lang)
 {
-  int i;
-
-  for (i = 0; i < languages_size; i++)
-    {
-      if (languages[i]->la_language == lang)
-	{
-	  return languages[i];
-	}
-    }
-  return NULL;
+  return languages[lang];
 }
 
 /* Return the language as a string.  */
+
 const char *
 language_str (enum language lang)
 {
-  int i;
-
-  for (i = 0; i < languages_size; i++)
-    {
-      if (languages[i]->la_language == lang)
-	{
-	  return languages[i]->la_name;
-	}
-    }
-  return "Unknown";
+  return languages[lang]->la_name;
 }
 
 static void
@@ -530,55 +522,45 @@ show_check (char *ignore, int from_tty)
   cmd_show_list (showchecklist, from_tty, "");
 }
 
-/* Add a language to the set of known languages.  */
 
-void
-add_language (const struct language_defn *lang)
-{
-  /* For the "set language" command.  */
-  static const char **language_names = NULL;
-  /* For the "help set language" command.  */
+/* Build and install the "set language LANG" command.  */
 
-  if (lang->la_magic != LANG_MAGIC)
-    {
-      fprintf_unfiltered (gdb_stderr,
-			  "Magic number of %s language struct wrong\n",
-			  lang->la_name);
-      internal_error (__FILE__, __LINE__,
-		      _("failed internal consistency check"));
-    }
+static void
+add_set_language_command ()
+{
+  static const char **language_names;
 
-  if (!languages)
-    {
-      languages_allocsize = DEFAULT_ALLOCSIZE;
-      languages = XNEWVEC (const struct language_defn *, languages_allocsize);
-    }
-  if (languages_size >= languages_allocsize)
+  /* Build the language names array, to be used as enumeration in the
+     "set language" enum command.  +1 for "local" and +1 for NULL
+     termination.  */
+  language_names = new const char *[ARRAY_SIZE (languages) + 2];
+
+  /* Display "auto", "local" and "unknown" first, and then the rest,
+     alpha sorted.  */
+  const char **language_names_p = language_names;
+  *language_names_p++ = auto_language_defn.la_name;
+  *language_names_p++ = "local";
+  *language_names_p++ = unknown_language_defn.la_name;
+  const char **sort_begin = language_names_p;
+  for (const auto &lang : languages)
     {
-      languages_allocsize *= 2;
-      languages = (const struct language_defn **) xrealloc ((char *) languages,
-				 languages_allocsize * sizeof (*languages));
+      /* Already handled above.  */
+      if (lang->la_language == language_auto
+	  || lang->la_language == language_unknown)
+	continue;
+      *language_names_p++ = lang->la_name;
     }
-  languages[languages_size++] = lang;
-
-  /* Build the language names array, to be used as enumeration in the
-     set language" enum command.  */
-  language_names = XRESIZEVEC (const char *, language_names,
-			       languages_size + 1);
-
-  for (int i = 0; i < languages_size; ++i)
-    language_names[i] = languages[i]->la_name;
-  language_names[languages_size] = NULL;
+  *language_names_p = NULL;
+  std::sort (sort_begin, language_names_p, compare_cstrings);
 
   /* Add the filename extensions.  */
-  if (lang->la_filename_extensions != NULL)
-    {
-      int i;
-
-      for (i = 0; lang->la_filename_extensions[i] != NULL; ++i)
-	add_filename_language (lang->la_filename_extensions[i],
-			       lang->la_language);
-    }
+  for (const auto &lang : languages)
+    if (lang->la_filename_extensions != NULL)
+      {
+	for (size_t i = 0; lang->la_filename_extensions[i] != NULL; ++i)
+	  add_filename_language (lang->la_filename_extensions[i],
+				 lang->la_language);
+      }
 
   /* Build the "help set language" docs.  */
   string_file doc;
@@ -587,24 +569,24 @@ add_language (const struct language_defn *lang)
 		"The currently understood settings are:\n\nlocal or "
 		"auto    Automatic setting based on source file\n"));
 
-  for (int i = 0; i < languages_size; ++i)
+  for (const auto &lang : languages)
     {
       /* Already dealt with these above.  */
-      if (languages[i]->la_language == language_unknown
-	  || languages[i]->la_language == language_auto)
+      if (lang->la_language == language_unknown
+	  || lang->la_language == language_auto)
 	continue;
 
       /* FIXME: i18n: for now assume that the human-readable name is
 	 just a capitalization of the internal name.  */
       doc.printf ("%-16s Use the %c%s language\n",
-		  languages[i]->la_name,
+		  lang->la_name,
 		  /* Capitalize first letter of language name.  */
-		  toupper (languages[i]->la_name[0]),
-		  languages[i]->la_name + 1);
+		  toupper (lang->la_name[0]),
+		  lang->la_name + 1);
     }
 
   add_setshow_enum_cmd ("language", class_support,
-			(const char **) language_names,
+			language_names,
 			&language,
 			doc.c_str (),
 			_("Show the current source language."),
@@ -620,13 +602,11 @@ add_language (const struct language_defn *lang)
 CORE_ADDR 
 skip_language_trampoline (struct frame_info *frame, CORE_ADDR pc)
 {
-  int i;
-
-  for (i = 0; i < languages_size; i++)
+  for (const auto &lang : languages)
     {
-      if (languages[i]->skip_trampoline)
+      if (lang->skip_trampoline != NULL)
 	{
-	  CORE_ADDR real_pc = (languages[i]->skip_trampoline) (frame, pc);
+	  CORE_ADDR real_pc = lang->skip_trampoline (frame, pc);
 
 	  if (real_pc)
 	    return real_pc;
@@ -919,53 +899,6 @@ const struct language_defn auto_language_defn =
   LANG_MAGIC
 };
 
-const struct language_defn local_language_defn =
-{
-  "local",
-  "Local",
-  language_auto,
-  range_check_off,
-  case_sensitive_on,
-  array_row_major,
-  macro_expansion_no,
-  NULL,
-  &exp_descriptor_standard,
-  unk_lang_parser,
-  unk_lang_error,
-  null_post_parser,
-  unk_lang_printchar,		/* Print character constant */
-  unk_lang_printstr,
-  unk_lang_emit_char,
-  unk_lang_print_type,		/* Print a type using appropriate syntax */
-  default_print_typedef,	/* Print a typedef using appropriate syntax */
-  unk_lang_val_print,		/* Print a value using appropriate syntax */
-  unk_lang_value_print,		/* Print a top-level value */
-  default_read_var_value,	/* la_read_var_value */
-  unk_lang_trampoline,		/* Language specific skip_trampoline */
-  "this", 		        /* name_of_this */
-  basic_lookup_symbol_nonlocal,	/* lookup_symbol_nonlocal */
-  basic_lookup_transparent_type,/* lookup_transparent_type */
-  unk_lang_demangle,		/* Language specific symbol demangler */
-  NULL,
-  unk_lang_class_name,		/* Language specific
-				   class_name_from_physname */
-  unk_op_print_tab,		/* expression operators for printing */
-  1,				/* c-style arrays */
-  0,				/* String lower bound */
-  default_word_break_characters,
-  default_collect_symbol_completion_matches,
-  unknown_language_arch_info,	/* la_language_arch_info.  */
-  default_print_array_index,
-  default_pass_by_reference,
-  default_get_string,
-  c_watch_location_expression,
-  NULL,				/* la_get_symbol_name_cmp */
-  iterate_over_symbols,
-  &default_varobj_ops,
-  NULL,
-  NULL,
-  LANG_MAGIC
-};
 
 /* Per-architecture language information.  */
 
@@ -982,16 +915,15 @@ static void *
 language_gdbarch_post_init (struct gdbarch *gdbarch)
 {
   struct language_gdbarch *l;
-  int i;
 
   l = GDBARCH_OBSTACK_ZALLOC (gdbarch, struct language_gdbarch);
-  for (i = 0; i < languages_size; i++)
-    {
-      if (languages[i] != NULL
-	  && languages[i]->la_language_arch_info != NULL)
-	languages[i]->la_language_arch_info
-	  (gdbarch, l->arch_info + languages[i]->la_language);
-    }
+  for (const auto &lang : languages)
+    if (lang != NULL && lang->la_language_arch_info != NULL)
+      {
+	lang->la_language_arch_info (gdbarch,
+				     l->arch_info + lang->la_language);
+      }
+
   return l;
 }
 
@@ -1205,9 +1137,7 @@ For Fortran the default is off; for other languages the default is on."),
 			show_case_command,
 			&setlist, &showlist);
 
-  add_language (&auto_language_defn);
-  add_language (&local_language_defn);
-  add_language (&unknown_language_defn);
+  add_set_language_command ();
 
   language = xstrdup ("auto");
   type = xstrdup ("auto");