gdb: add support for disassembler styling using libopcodes

This commit extends GDB to make use of libopcodes styling support
where available, currently this is just i386 based architectures, and
RISC-V.

For architectures that don't support styling using libopcodes GDB will
fall back to using the Python Pygments package, when the package is
available.

The new libopcodes based styling has the disassembler identify parts
of the disassembled instruction, e.g. registers, immediates,
mnemonics, etc, and can style these components differently.
Additionally, as the styling is now done in GDB we can add settings to
allow the user to configure which colours are used right from the GDB
CLI.

There's some new maintenance commands:

  maintenance set libopcodes-styling enabled on|off
  maintenance show libopcodes-styling

These can be used to manually disable use of libopcodes styling.  This
is a maintenance command as it's not anticipated that a user should
need to do this.  But, this could be useful for testing, or, in some
rare cases, a user might want to override the Python hook used for
disassembler styling, and then disable libopcode styling so that GDB
falls back to using Python.  Right now I would consider this second
use case a rare situation, which is why I think a maintenance command
is appropriate.

When libopcodes is being used for styling then the user can make use
of the following new styles:

  set/show style disassembler comment
  set/show style disassembler immediate
  set/show style disassembler mnemonic
  set/show style disassembler register

The disassembler also makes use of the 'address' and 'function'
styles to style some parts of the disassembler output.  I have also
added the following aliases though:

  set/show style disassembler address
  set/show style disassembler symbol

these are aliases for:

  set/show style address
  set/show style function

respectively, and exist to make it easier for users to discover
disassembler related style settings.  The 'address' style is used to
style numeric addresses in the disassembler output, while the 'symbol'
or 'function' style is used to style the names of symbols in
disassembler output.

As not every architecture supports libopcodes styling, the maintenance
setting 'libopcodes-styling enabled' has an "auto-off" type behaviour.
Consider this GDB session:

  (gdb) show architecture
  The target architecture is set to "auto" (currently "i386:x86-64").
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "on".

the setting defaults to "on" for architectures that support libopcodes
based styling.

  (gdb) set architecture sparc
  The target architecture is set to "sparc".
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "off" (not supported on architecture "sparc")

the setting will show as "off" if the user switches to an architecture
that doesn't support libopcodes styling.  The underlying setting is
still "on" at this point though, if the user switches back to
i386:x86-64 then the setting would go back to being "on".

  (gdb) maintenance set libopcodes-styling enabled off
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "off".

now the setting is "off" for everyone, even if the user switches back
to i386:x86-64 the setting will still show as "off".

  (gdb) maintenance set libopcodes-styling enabled on
  Use of libopcodes styling not supported on architecture "sparc".
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "off".

attempting to switch the setting "on" for an unsupported architecture
will give an error, and the setting will remain "off".

  (gdb) set architecture auto
  The target architecture is set to "auto" (currently "i386:x86-64").
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "off".
  (gdb) maintenance set libopcodes-styling enabled on
  (gdb) maintenance show libopcodes-styling enabled
  Use of libopcodes styling support is "on".

the user will need to switch back to a supported architecture before
they can one again turn this setting "on".

6 files changed, 439 insertions, 26 deletions

diff --git a/gdb/NEWS b/gdb/NEWS
index 1178a37..742f4fe 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -39,6 +39,12 @@
    set width NUMBER
    set width unlimited
 
+* Disassembler styling using libopcodes.  GDB now supports
+  disassembler styling using libopcodes.  This is only available for
+  some targets (currently x86 and RISC-V).  For unsupported targets
+  Python Pygments is still used.  For supported targets, libopcodes
+  styling is used by default.
+
 * New commands
 
 maintenance set ignore-prologue-end-flag on|off
@@ -53,6 +59,28 @@ show print nibbles
   This controls whether the 'print/t' command will display binary values
   in groups of four bits, known as "nibbles".  The default is 'off'.
 
+maintenance set libopcodes-styling on|off
+maintenance show libopcodes-styling
+  These can be used to force off libopcodes based styling, the Python
+  Pygments styling will then be used instead.
+
+set style disassembler comment
+show style disassembler comment
+set style disassembler immediate
+show style disassembler immediate
+set style disassembler mnemonic
+show style disassembler mnemonic
+set style disassembler register
+show style disassembler register
+set style disassembler address
+show style disassembler address
+set style disassembler symbol
+show style disassembler symbol
+  For targets that support libopcodes based styling, these settings
+  control how various aspects of the disassembler output are styled.
+  The 'disassembler address' and 'disassembler symbol' styles are
+  aliases for the 'address' and 'function' styles respectively.
+
 * Changed commands
 
 maintenance info line-table
diff --git a/gdb/cli/cli-style.c b/gdb/cli/cli-style.c
index 3fd85f4..abf6855 100644
--- a/gdb/cli/cli-style.c
+++ b/gdb/cli/cli-style.c
@@ -110,6 +110,23 @@ cli_style_option version_style ("version", ui_file_style::MAGENTA,
 
 /* See cli-style.h.  */
 
+cli_style_option disasm_mnemonic_style ("mnemonic", ui_file_style::GREEN);
+
+/* See cli-style.h.  */
+
+cli_style_option disasm_register_style ("register", ui_file_style::RED);
+
+/* See cli-style.h.  */
+
+cli_style_option disasm_immediate_style ("immediate", ui_file_style::BLUE);
+
+/* See cli-style.h.  */
+
+cli_style_option disasm_comment_style ("comment", ui_file_style::WHITE,
+				       ui_file_style::DIM);
+
+/* See cli-style.h.  */
+
 cli_style_option::cli_style_option (const char *name,
 				    ui_file_style::basic_color fg,
 				    ui_file_style::intensity intensity)
@@ -224,15 +241,16 @@ cli_style_option::do_show_intensity (struct ui_file *file, int from_tty,
 
 /* See cli-style.h.  */
 
-void
+set_show_commands
 cli_style_option::add_setshow_commands (enum command_class theclass,
 					const char *prefix_doc,
 					struct cmd_list_element **set_list,
 					struct cmd_list_element **show_list,
 					bool skip_intensity)
 {
-  add_setshow_prefix_cmd (m_name, theclass, prefix_doc, prefix_doc,
-			  &m_set_list, &m_show_list, set_list, show_list);
+  set_show_commands prefix_cmds
+    = add_setshow_prefix_cmd (m_name, theclass, prefix_doc, prefix_doc,
+			      &m_set_list, &m_show_list, set_list, show_list);
 
   set_show_commands commands;
 
@@ -274,6 +292,8 @@ cli_style_option::add_setshow_commands (enum command_class theclass,
       commands.set->set_context (this);
       commands.show->set_context (this);
     }
+
+  return prefix_cmds;
 }
 
 static cmd_list_element *style_set_list;
@@ -387,11 +407,13 @@ Configure filename colors and display intensity."),
 					&style_set_list, &style_show_list,
 					false);
 
-  function_name_style.add_setshow_commands (no_class, _("\
+  set_show_commands function_prefix_cmds
+    = function_name_style.add_setshow_commands (no_class, _("\
 Function name display styling.\n\
 Configure function name colors and display intensity"),
-					    &style_set_list, &style_show_list,
-					    false);
+						&style_set_list,
+						&style_show_list,
+						false);
 
   variable_name_style.add_setshow_commands (no_class, _("\
 Variable name display styling.\n\
@@ -399,11 +421,12 @@ Configure variable name colors and display intensity"),
 					    &style_set_list, &style_show_list,
 					    false);
 
-  address_style.add_setshow_commands (no_class, _("\
+  set_show_commands address_prefix_cmds
+    = address_style.add_setshow_commands (no_class, _("\
 Address display styling.\n\
 Configure address colors and display intensity"),
-				      &style_set_list, &style_show_list,
-				      false);
+					  &style_set_list, &style_show_list,
+					  false);
 
   title_style.add_setshow_commands (no_class, _("\
 Title display styling.\n\
@@ -451,4 +474,70 @@ Version string display styling.\n\
 Configure colors used to display the GDB version string."),
 				      &style_set_list, &style_show_list,
 				      false);
+
+  disasm_mnemonic_style.add_setshow_commands (no_class, _("\
+Disassembler mnemonic display styling.\n\
+Configure the colors and display intensity for instruction mnemonics\n\
+in the disassembler output.  The \"disassembler mnemonic\" style is\n\
+used to display instruction mnemonics as well as any assembler\n\
+directives, e.g. \".byte\", \".word\", etc.\n\
+\n\
+This style will only be used for targets that support libopcodes based\n\
+disassembler styling.  When Python Pygments based styling is used\n\
+then this style has no effect."),
+					      &style_disasm_set_list,
+					      &style_disasm_show_list,
+					      false);
+
+  disasm_register_style.add_setshow_commands (no_class, _("\
+Disassembler register display styling.\n\
+Configure the colors and display intensity for registers in the\n\
+disassembler output.\n\
+\n\
+This style will only be used for targets that support libopcodes based\n\
+disassembler styling.  When Python Pygments based styling is used\n\
+then this style has no effect."),
+					      &style_disasm_set_list,
+					      &style_disasm_show_list,
+					      false);
+
+  disasm_immediate_style.add_setshow_commands (no_class, _("\
+Disassembler immediate display styling.\n\
+Configure the colors and display intensity for immediates in the\n\
+disassembler output.  The \"disassembler immediate\" style is used for\n\
+any number that is not an address, this includes constants in arithmetic\n\
+instructions, as well as address offsets in memory access instructions.\n\
+\n\
+This style will only be used for targets that support libopcodes based\n\
+disassembler styling.  When Python Pygments based styling is used\n\
+then this style has no effect."),
+					       &style_disasm_set_list,
+					       &style_disasm_show_list,
+					       false);
+
+  disasm_comment_style.add_setshow_commands (no_class, _("\
+Disassembler comment display styling.\n\
+Configure the colors and display intensity for comments in the\n\
+disassembler output.  The \"disassembler comment\" style is used for\n\
+the comment character, and everything after the comment character up to\n\
+the end of the line.  The comment style overrides any other styling,\n\
+e.g. a register name in a comment will use the comment styling.\n\
+\n\
+This style will only be used for targets that support libopcodes based\n\
+disassembler styling.  When Python Pygments based styling is used\n\
+then this style has no effect."),
+					     &style_disasm_set_list,
+					     &style_disasm_show_list,
+					     false);
+
+  /* Setup 'disassembler address' style and 'disassembler symbol' style,
+     these are aliases for 'address' and 'function' styles respectively.  */
+  add_alias_cmd ("address", address_prefix_cmds.set, no_class, 0,
+		 &style_disasm_set_list);
+  add_alias_cmd ("address", address_prefix_cmds.show, no_class, 0,
+		 &style_disasm_show_list);
+  add_alias_cmd ("symbol", function_prefix_cmds.set, no_class, 0,
+		 &style_disasm_set_list);
+  add_alias_cmd ("symbol", function_prefix_cmds.show, no_class, 0,
+		 &style_disasm_show_list);
 }
diff --git a/gdb/cli/cli-style.h b/gdb/cli/cli-style.h
index f69df47..4090cf0 100644
--- a/gdb/cli/cli-style.h
+++ b/gdb/cli/cli-style.h
@@ -43,12 +43,13 @@ public:
   /* Return the style name.  */
   const char *name () { return m_name; };
 
-  /* Call once to register this CLI style with the CLI engine.  */
-  void add_setshow_commands (enum command_class theclass,
-			     const char *prefix_doc,
-			     struct cmd_list_element **set_list,
-			     struct cmd_list_element **show_list,
-			     bool skip_intensity);
+  /* Call once to register this CLI style with the CLI engine.  Returns
+     the set/show prefix commands for the style.  */
+  set_show_commands add_setshow_commands (enum command_class theclass,
+					  const char *prefix_doc,
+					  struct cmd_list_element **set_list,
+					  struct cmd_list_element **show_list,
+					  bool skip_intensity);
 
   /* Return the 'set style NAME' command list, that can be used
      to build a lambda DO_SET to call add_setshow_commands.  */
@@ -116,6 +117,21 @@ extern cli_style_option title_style;
 /* The metadata style.  */
 extern cli_style_option metadata_style;
 
+/* The disassembler style for mnemonics or assembler directives
+   (e.g. '.byte', etc).  */
+extern cli_style_option disasm_mnemonic_style;
+
+/* The disassembler style for register names.  */
+extern cli_style_option disasm_register_style;
+
+/* The disassembler style for numerical values that are not addresses, this
+   includes immediate operands (e.g. in, an add instruction), but also
+   address offsets (e.g. in a load instruction).  */
+extern cli_style_option disasm_immediate_style;
+
+/* The disassembler style for comments.  */
+extern cli_style_option disasm_comment_style;
+
 /* The border style of a TUI window that does not have the focus.  */
 extern cli_style_option tui_border_style;
 
diff --git a/gdb/disasm.c b/gdb/disasm.c
index 6c64c14..cf27a32 100644
--- a/gdb/disasm.c
+++ b/gdb/disasm.c
@@ -41,6 +41,63 @@
    which is set by the "set disassembler_options" command.  */
 static std::string prospective_options;
 
+/* When this is true we will try to use libopcodes to provide styling to
+   the disassembler output.  */
+
+static bool use_libopcodes_styling = true;
+
+/* To support the set_use_libopcodes_styling function we have a second
+   variable which is connected to the actual set/show option.  */
+
+static bool use_libopcodes_styling_option = use_libopcodes_styling;
+
+/* The "maint show libopcodes-styling enabled" command.  */
+
+static void
+show_use_libopcodes_styling  (struct ui_file *file, int from_tty,
+			      struct cmd_list_element *c,
+			      const char *value)
+{
+  gdb_non_printing_memory_disassembler dis (target_gdbarch ());
+  bool supported = dis.disasm_info ()->created_styled_output;
+
+  if (supported || !use_libopcodes_styling)
+    gdb_printf (file, _("Use of libopcodes styling support is \"%s\".\n"),
+		value);
+  else
+    {
+      /* Use of libopcodes styling is not supported, and the user has this
+	 turned on!  */
+      gdb_printf (file, _("Use of libopcodes styling support is \"off\""
+			  " (not supported on architecture \"%s\")\n"),
+		  gdbarch_bfd_arch_info (target_gdbarch ())->printable_name);
+    }
+}
+
+/* The "maint set libopcodes-styling enabled" command.  */
+
+static void
+set_use_libopcodes_styling (const char *args, int from_tty,
+			    struct cmd_list_element *c)
+{
+  gdb_non_printing_memory_disassembler dis (target_gdbarch ());
+  bool supported = dis.disasm_info ()->created_styled_output;
+
+  /* If the current architecture doesn't support libopcodes styling then we
+     give an error here, but leave the underlying setting enabled.  This
+     means that if the user switches to an architecture that does support
+     libopcodes styling the setting will be enabled.  */
+
+  if (use_libopcodes_styling_option && !supported)
+    {
+      use_libopcodes_styling_option = use_libopcodes_styling;
+      error (_("Use of libopcodes styling not supported on architecture \"%s\"."),
+	     gdbarch_bfd_arch_info (target_gdbarch ())->printable_name);
+    }
+  else
+    use_libopcodes_styling = use_libopcodes_styling_option;
+}
+
 /* This structure is used to store line number information for the
    deprecated /m option.
    We need a different sort of line table from the normal one cuz we can't
@@ -160,7 +217,26 @@ gdb_disassembler::dis_asm_print_address (bfd_vma addr,
   gdb_disassembler *self
     = static_cast<gdb_disassembler *>(info->application_data);
 
-  print_address (self->arch (), addr, self->stream ());
+  if (self->in_comment_p ())
+    {
+      /* Calling 'print_address' might add styling to the output (based on
+	 the properties of the stream we're writing too).  This is usually
+	 fine, but if we are in an assembler comment then we'd prefer to
+	 have the comment style, rather than the default address style.
+
+	 Print the address into a temporary buffer which doesn't support
+	 styling, then reprint this unstyled address with the default text
+	 style.
+
+	 As we are inside a comment right now, the standard print routine
+	 will ensure that the comment is printed to the user with a
+	 suitable comment style.  */
+      string_file tmp;
+      print_address (self->arch (), addr, &tmp);
+      self->fprintf_styled_func (self, dis_style_text, "%s", tmp.c_str ());
+    }
+  else
+    print_address (self->arch (), addr, self->stream ());
 }
 
 /* See disasm.h.  */
@@ -202,11 +278,54 @@ gdb_printing_disassembler::fprintf_styled_func (void *dis_info,
 						const char *format, ...)
 {
   ui_file *stream = stream_from_gdb_disassemble_info (dis_info);
+  gdb_printing_disassembler *dis = (gdb_printing_disassembler *) dis_info;
 
   va_list args;
   va_start (args, format);
-  gdb_vprintf (stream, format, args);
+  std::string content = string_vprintf (format, args);
   va_end (args);
+
+  /* Once in a comment then everything should be styled as a comment.  */
+  if (style == dis_style_comment_start)
+    dis->set_in_comment (true);
+  if (dis->in_comment_p ())
+    style = dis_style_comment_start;
+
+  /* Now print the content with the correct style.  */
+  const char *txt = content.c_str ();
+  switch (style)
+    {
+    case dis_style_mnemonic:
+    case dis_style_assembler_directive:
+      fputs_styled (txt, disasm_mnemonic_style.style (), stream);
+      break;
+
+    case dis_style_register:
+      fputs_styled (txt, disasm_register_style.style (), stream);
+      break;
+
+    case dis_style_immediate:
+    case dis_style_address_offset:
+      fputs_styled (txt, disasm_immediate_style.style (), stream);
+      break;
+
+    case dis_style_address:
+      fputs_styled (txt, address_style.style (), stream);
+      break;
+
+    case dis_style_symbol:
+      fputs_styled (txt, function_name_style.style (), stream);
+      break;
+
+    case dis_style_comment_start:
+      fputs_styled (txt, disasm_comment_style.style (), stream);
+      break;
+
+    case dis_style_text:
+      gdb_puts (txt, stream);
+      break;
+    }
+
   /* Something non -ve.  */
   return 0;
 }
@@ -818,7 +937,20 @@ gdb_disassembler::gdb_disassembler (struct gdbarch *gdbarch,
 				    read_memory_ftype func)
   : gdb_printing_disassembler (gdbarch, &m_buffer, func,
 			       dis_asm_memory_error, dis_asm_print_address),
-    m_buffer (!use_ext_lang_colorization_p && disassembler_styling
+    /* The use of m_di.created_styled_output here is a bit of a cheat, but
+       it works fine for now.  Currently, for all targets that support
+       libopcodes styling, this field is set during the call to
+       disassemble_init_for_target, which was called as part of the
+       initialization of gdb_printing_disassembler.  And so, we are able to
+       spot if a target supports libopcodes styling, and create m_buffer in
+       the correct styling mode.
+
+       If there's ever a target that only sets created_styled_output during
+       the actual disassemble phase, then the logic here will have to
+       change.  */
+    m_buffer ((!use_ext_lang_colorization_p
+	       || (use_libopcodes_styling && m_di.created_styled_output))
+	      && disassembler_styling
 	      && file->can_emit_style_escape ()),
     m_dest (file)
 { /* Nothing.  */ }
@@ -903,14 +1035,17 @@ gdb_disassembler::print_insn (CORE_ADDR memaddr,
 {
   m_err_memaddr.reset ();
   m_buffer.clear ();
+  this->set_in_comment (false);
 
   int length = gdb_print_insn_1 (arch (), memaddr, &m_di);
 
-  /* If we have successfully disassembled an instruction, styling is on, we
-     think that the extension language might be able to perform styling for
-     us, and the destination can support styling, then lets call into the
-     extension languages in order to style this output.  */
+  /* If we have successfully disassembled an instruction, disassembler
+     styling using the extension language is on, and libopcodes hasn't
+     already styled the output for us, and, if the destination can support
+     styling, then lets call into the extension languages in order to style
+     this output.  */
   if (length > 0 && disassembler_styling
+      && (!m_di.created_styled_output || !use_libopcodes_styling)
       && use_ext_lang_colorization_p
       && m_dest->can_emit_style_escape ())
     {
@@ -1311,4 +1446,39 @@ Show the disassembler options."), NULL,
 					 show_disassembler_options_sfunc,
 					 &setlist, &showlist);
   set_cmd_completer (set_show_disas_opts.set, disassembler_options_completer);
+
+
+  /* All the 'maint set|show libopcodes-styling' sub-commands.  */
+  static struct cmd_list_element *maint_set_libopcodes_styling_cmdlist;
+  static struct cmd_list_element *maint_show_libopcodes_styling_cmdlist;
+
+  /* Adds 'maint set|show libopcodes-styling'.  */
+  add_setshow_prefix_cmd ("libopcodes-styling", class_maintenance,
+			  _("Set libopcodes-styling specific variables."),
+			  _("Show libopcodes-styling specific variables."),
+			  &maint_set_libopcodes_styling_cmdlist,
+			  &maint_show_libopcodes_styling_cmdlist,
+			  &maintenance_set_cmdlist,
+			  &maintenance_show_cmdlist);
+
+  /* Adds 'maint set|show gnu-source-highlight enabled'.  */
+  add_setshow_boolean_cmd ("enabled", class_maintenance,
+			   &use_libopcodes_styling_option, _("\
+Set whether the libopcodes styling support should be used."), _("\
+Show whether the libopcodes styling support should be used."),_("\
+When enabled, GDB will try to make use of the builtin libopcodes styling\n\
+support, to style the disassembler output.  Not every architecture has\n\
+styling support within libopcodes, so enabling this is not a guarantee\n\
+that libopcodes styling will be available.\n\
+\n\
+When this option is disabled, GDB will make use of the Python Pygments\n\
+package (if available) to style the disassembler output.\n\
+\n\
+All disassembler styling can be disabled with:\n\
+\n\
+  set style disassembler enabled off"),
+			   set_use_libopcodes_styling,
+			   show_use_libopcodes_styling,
+			   &maint_set_libopcodes_styling_cmdlist,
+			   &maint_show_libopcodes_styling_cmdlist);
 }
diff --git a/gdb/disasm.h b/gdb/disasm.h
index 54176eb..2921d53 100644
--- a/gdb/disasm.h
+++ b/gdb/disasm.h
@@ -138,6 +138,16 @@ protected:
 				  const char *format, ...)
     ATTRIBUTE_PRINTF(3,4);
 
+  /* Return true if the disassembler is considered inside a comment, false
+     otherwise.  */
+  bool in_comment_p () const
+  { return m_in_comment; }
+
+  /* Set whether the disassembler should be considered as within comment
+     text or not.  */
+  void set_in_comment (bool c)
+  { m_in_comment = c; }
+
 private:
 
   /* When libopcodes calls the fprintf_func and fprintf_styled_func
@@ -151,6 +161,12 @@ private:
 
   /* The stream to which output should be sent.  */
   struct ui_file *m_stream;
+
+  /* Are we inside a comment?  This will be set true if the disassembler
+     uses styled output and emits a start of comment character.  It is up
+     to the code that uses this disassembler class to reset this flag back
+     to false at a suitable time (e.g. at the end of every line).  */
+  bool m_in_comment;
 };
 
 /* A basic disassembler that doesn't actually print anything.  */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index 7a4e337..86394f6 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -26526,6 +26526,7 @@ then it will be used.
 @item show style sources
 Show the current state of source code styling.
 
+@anchor{style_disassembler_enabled}
 @item set style disassembler enabled @samp{on|off}
 Enable or disable disassembler styling.  This affects whether
 disassembler output, such as the output of the @code{disassemble}
@@ -26533,13 +26534,32 @@ command, is styled.  Disassembler styling only works if styling in
 general is enabled (with @code{set style enabled on}), and if a source
 highlighting library is available to @value{GDBN}.
 
-To highlight disassembler output, @value{GDBN} must be compiled with
-Python support, and the Python Pygments package must be available.  If
-these requirements are not met then @value{GDBN} will not highlight
-disassembler output, even when this option is @samp{on}.
+The two source highlighting libraries that @value{GDBN} could use to
+style disassembler output are; @value{GDBN}'s builtin disassembler, or
+the Python Pygments package.
+
+@value{GDBN}'s first choice will be to use the builtin disassembler
+for styling, this usually provides better results, being able to style
+different types of instruction operands differently.  However, the
+builtin disassembler is not able to style all architectures.
+
+For architectures that the builtin disassembler is unable to style,
+@value{GDBN} will fall back to use the Python Pygments package where
+possible.  In order to use the Python Pygments package, @value{GDBN}
+must be built with Python support, and the Pygments package must be
+installed.
+
+If neither of these options are available then @value{GDBN} will
+produce unstyled disassembler output, even when this setting is
+@samp{on}.
+
+To discover if the current architecture supports styling using the
+builtin disassembler library see @ref{maint_libopcodes_styling,,@kbd{maint
+show libopcodes-styling enabled}}.
 
 @item show style disassembler enabled
 Show the current state of disassembler styling.
+
 @end table
 
 Subcommands of @code{set style} control specific forms of styling.
@@ -26584,6 +26604,11 @@ Control the styling of function names.  These are managed with the
 @code{set style function} family of commands.  By default, this
 style's foreground color is yellow.
 
+This style is also used for symbol names in styled disassembler output
+if @value{GDBN} is using its builtin disassembler library for styling
+(@pxref{style_disassembler_enabled,,@kbd{set style disassembler
+enabled}}).
+
 @item variable
 Control the styling of variable names.  These are managed with the
 @code{set style variable} family of commands.  By default, this style's
@@ -26594,6 +26619,11 @@ Control the styling of addresses.  These are managed with the
 @code{set style address} family of commands.  By default, this style's
 foreground color is blue.
 
+This style is also used for addresses in styled disassembler output
+if @value{GDBN} is using its builtin disassembler library for styling
+(@pxref{style_disassembler_enabled,,@kbd{set style disassembler
+enabled}}).
+
 @item version
 Control the styling of @value{GDBN}'s version number text.  By
 default, this style's foreground color is magenta and it has bold
@@ -26642,6 +26672,47 @@ general styling to @value{GDBN}.  @xref{TUI Configuration}.
 Control the styling of the active TUI border; that is, the TUI window
 that has the focus.
 
+@item disassembler comment
+Control the styling of comments in the disassembler output.  These are
+managed with the @code{set style disassembler comment} family of
+commands.  This style is only used when @value{GDBN} is styling using
+its builtin disassembler library
+(@pxref{style_disassembler_enabled,,@kbd{set style disassembler
+enabled}}).  By default, this style's intensity is dim, and its
+foreground color is white.
+
+@item disassembler immediate
+Control the styling of numeric operands in the disassembler output.
+These are managed with the @code{set style disassembler immediate}
+family of commands.  This style is not used for instruction operands
+that represent addresses, in that case the @samp{disassembler address}
+style is used.  This style is only used when @value{GDBN} is styling
+using its builtin disassembler library.  By default, this style's
+foreground color is blue.
+
+@item disassembler address
+Control the styling of address operands in the disassembler output.
+This is an alias for the @samp{address} style.
+
+@item disassembler symbol
+Control the styling of symbol names in the disassembler output.  This
+is an alias for the @samp{function} style.
+
+@item disassembler mnemonic
+Control the styling of instruction mnemonics in the disassembler
+output.  These are managed with the @code{set style disassembler
+mnemonic} family of commands.  This style is also used for assembler
+directives, e.g.@: @code{.byte}, @code{.word}, etc.  This style is
+only used when @value{GDBN} is styling using its builtin disassembler
+library.  By default, this style's foreground color is green.
+
+@item disassembler register
+Control the styling of register operands in the disassembler output.
+These are managed with the @code{set style disassembler register}
+family of commands.  This style is only used when @value{GDBN} is
+styling using its builtin disassembler library.  By default, this style's
+foreground color is red.
+
 @end table
 
 @node Numbers
@@ -40415,6 +40486,29 @@ This option is useful for debugging @value{GDBN}'s use of the Pygments
 library when @value{GDBN} is linked against the GNU Source Highlight
 library.
 
+@anchor{maint_libopcodes_styling}
+@kindex maint set libopcodes-styling enabled
+@kindex maint show libopcodes-styling enabled
+@item maint set libopcodes-styling enabled @r{[}on|off@r{]}
+@itemx maint show libopcodes-styling enabled
+Control whether @value{GDBN} should use its builtin disassembler
+(@file{libopcodes}) to style disassembler output (@pxref{Output
+Styling}).  The builtin disassembler does not support styling for all
+architectures.
+
+When this option is @samp{off} the builtin disassembler will not be
+used for styling, @value{GDBN} will fall back to using the Python
+Pygments package if possible.
+
+Trying to set this option @samp{on} for an architecture that the
+builtin disassembler is unable to style will give an error, otherwise,
+the builtin disassembler will be used to style disassembler output.
+
+This option is @samp{on} by default for supported architectures.
+
+This option is useful for debugging @value{GDBN}'s use of the Pygments
+library when @value{GDBN} is built for an architecture that supports
+styling with the builtin disassembler
 @kindex maint space
 @cindex memory used by commands
 @item maint space @var{value}