Introduce class completion_tracker & rewrite completion<->readline interaction

This patch reworks the whole completion machinery, and prepares it
for later enhancements.

Adds a new "completion_tracker" class that is meant to hold everything
about the state of the current completion operation.

This class now has the responsibility of tracking the list of
completion matches, and checking whether the max completions limit has
been reached.  You can look at this as this patch starting out by
C++fying the existing "completion_tracker" in symtab.c (it's just an
htab_t typedef currently), moving it to completer.h/c, and then making
it a class/generalizing/enhancing it.

Unlike with the current tracking, completion_tracker now checks
whether the limit has been reached on each completion match list
insertion.  This both simplifies the max-completions handling code
(maybe_add_completion_enum is gone, for example), and is a
prerequisite for follow up patches.

The current completion_tracker is only used for symbol completions,
and the symbol code gets at the current instance via globals.  This
patch cleans that up by adding a completion_tracker reference to the
signature of the completion functions, and passing the tracker around
everywhere necessary.

Then, the patch changes how the completion match list is handed over
to readline.  Currently, we're using the rl_completion_entry_function
readline entry point, and the patch switches to
rl_attempted_completion_function.  A following patch will want to let
GDB itself decide the common completion prefix between all matches
(what readline calls the "lowest common denominator"), instead of
having readline compute it, and that's not possible with the
rl_completion_entry_function entry point.  Also,
rl_attempted_completion_function lets GDB hand over the match list to
readline as an array in one go instead of passing down matches one by
one, so from that angle it's a nicer entry point anyway.

Lastly, the patch catches exceptions around the readline entry points,
because we can't let C++ exceptions cross readline.  We handle that in
the readline input entry point, but the completion entry point isn't
guarded, so GDB can abort if completion throws.  E.g., in current
master:

 (gdb) b -function "fun<tab>
 terminate called after throwing an instance of 'gdb_exception_RETURN_MASK_ERROR'
 Aborted (core dumped)

This patch fixes that.  This will be exercised in the new tests added
later on in the series.

gdb/ChangeLog:
2017-07-17  Pedro Alves  <palves@redhat.com>

	* ada-lang.c (symbol_completion_match): Adjust comments.
	(symbol_completion_add): Replace vector parameter with
	completion_tracker parameter.  Use it.
	(ada_make_symbol_completion_list): Rename to...
	(ada_collect_symbol_completion_matches): ... this.  Add
	completion_tracker parameter and use it.
	(ada_language_defn): Adjust.
	* break-catch-syscall.c (catch_syscall_completer): Adjust
	prototype and work with completion_tracker instead of VEC.
	* breakpoint.c (condition_completer): Adjust prototype and work
	with completion_tracker instead of VEC.
	* c-lang.c (c_language_defn, cplus_language_defn)
	(asm_language_defn, minimal_language_defn): Adjust to renames.
	* cli/cli-cmds.c (complete_command): Rework using
	completion_tracker.  Catch exceptions when completing.
	* cli/cli-decode.c (integer_unlimited_completer)
	(complete_on_cmdlist, complete_on_enum): Adjust prototype and work
	with completion_tracker instead of VEC.
	* command.h (struct completion_tracker): Forward declare.
	(completer_ftype, completer_handle_brkchars_ftype): Change
	types.
	(complete_on_cmdlist, complete_on_enum): Adjust.
	* completer.c: Include <algorithm>.
	(struct gdb_completer_state): New.
	(current_completion): New global.
	(readline_line_completion_function): Delete.
	(noop_completer, filename_completer)
	(filename_completer_handle_brkchars, complete_files_symbols)
	(linespec_location_completer): Adjust to work with a
	completion_tracker instead of a VEC.
	(string_or_empty): New.
	(collect_explicit_location_matches): Adjust to work with a
	completion_tracker instead of a VEC.
	(explicit_location_completer): Rename to ...
	(complete_explicit_location): ... this and adjust to work with a
	completion_tracker instead of a VEC.
	(location_completer): Adjust to work with a completion_tracker
	instead of a VEC.
	(add_struct_fields): Adjust to work with a completion_list instead
	of VEC.
	(expression_completer): Rename to ...
	(complete_expression): ... this and adjust to work with a
	completion_tracker instead of a VEC.  Use complete_files_symbols.
	(expression_completer): Reimplement on top of complete_expression.
	(symbol_completer): Adjust to work with a completion_tracker
	instead of a VEC.
	(enum complete_line_internal_reason): Add describing comments.
	(complete_line_internal_normal_command): Adjust to work with a
	completion_tracker instead of a VEC.
	(complete_line_internal): Rename to ...
	(complete_line_internal_1): ... this and adjust to work with a
	completion_tracker instead of a VEC.  Assert TEXT is NULL in the
	handle_brkchars phase.
	(new_completion_tracker): Delete.
	(complete_line_internal): Reimplement as TRY/CATCH wrapper around
	complete_line_internal_1.
	(free_completion_tracker): Delete.
	(INITIAL_COMPLETION_HTAB_SIZE): New.
	(completion_tracker::completion_tracker)
	(completion_tracker::~completion_tracker): New.
	(maybe_add_completion): Delete.
	(completion_tracker::maybe_add_completion)
	(completion_tracker::add_completion)
	(completion_tracker::add_completions): New.
	(throw_max_completions_reached_error): Delete.
	(complete_line): Adjust to work with a completion_tracker instead
	of a VEC.  Don't create a completion_tracker_t or check for max
	completions here.
	(command_completer, command_completer_handle_brkchars)
	(signal_completer, reg_or_group_completer_1)
	(reg_or_group_completer, default_completer_handle_brkchars):
	Adjust to work with a completion_tracker.
	(gdb_completion_word_break_characters_throw): New.
	(gdb_completion_word_break_characters): Reimplement.
	(line_completion_function): Delete.
	(completion_tracker::recompute_lowest_common_denominator)
	(expand_preserving_ws)
	(completion_tracker::build_completion_result)
	(completion_result::completion_result)
	(completion_result::completion_result)
	(completion_result::~completion_result)
	(completion_result::completion_result)
	(completion_result::release_match_list, compare_cstrings)
	(completion_result::sort_match_list)
	(completion_result::reset_match_list)
	(gdb_rl_attempted_completion_function_throw)
	(gdb_rl_attempted_completion_function): New.
	* completer.h (completion_list, struct completion_result)
	(class completion_tracker): New.
	(complete_line): Add completion_tracker parameter.
	(readline_line_completion_function): Delete.
	(gdb_rl_attempted_completion_function): New.
	(noop_completer, filename_completer, expression_completer)
	(location_completer, symbol_completer, command_completer)
	(signal_completer, reg_or_group_completer): Update prototypes.
	(completion_tracker_t, new_completion_tracker)
	(make_cleanup_free_completion_tracker): Delete.
	(enum maybe_add_completion_enum): Delete.
	(maybe_add_completion): Delete.
	(throw_max_completions_reached_error): Delete.
	* corefile.c (complete_set_gnutarget): Adjust to work with a
	completion_tracker instead of a VEC.
	* cp-abi.c (cp_abi_completer): Adjust to work with a
	completion_tracker instead of a VEC.
	* d-lang.c (d_language_defn): Adjust.
	* disasm.c (disassembler_options_completer): Adjust to work with a
	completion_tracker instead of a VEC.
	* f-lang.c (f_make_symbol_completion_list): Rename to ...
	(f_collect_symbol_completion_matches): ... this.  Adjust to work
	with a completion_tracker instead of a VEC.
	(f_language_defn): Adjust.
	* go-lang.c (go_language_defn): Adjust.
	* guile/scm-cmd.c (cmdscm_add_completion, cmdscm_completer):
	Adjust to work with a completion_tracker instead of a VEC.
	* infrun.c (handle_completer): Likewise.
	* interps.c (interpreter_completer): Likewise.
	* interps.h (interpreter_completer): Likewise.
	* language.c (unknown_language_defn, auto_language_defn)
	(local_language_defn): Adjust.
	* language.h (language_defn::la_make_symbol_completion_list):
	Rename to ...
	(language_defn::la_collect_symbol_completion_matches): ... this
	and adjust to work with a completion_tracker instead of a VEC.
	* m2-lang.c (m2_language_defn): Adjust.
	* objc-lang.c (objc_language_defn): Adjust.
	* opencl-lang.c (opencl_language_defn): Adjust.
	* p-lang.c (pascal_language_defn): Adjust.
	* python/py-cmd.c (cmdpy_completer_helper): Handle NULL word.
	(cmdpy_completer_handle_brkchars, cmdpy_completer): Adjust to work
	with a completion_tracker.
	* rust-lang.c (rust_language_defn): Adjust.
	* symtab.c (free_completion_list, do_free_completion_list)
	(return_val, completion_tracker): Delete.
	(completion_list_add_name, completion_list_add_symbol)
	(completion_list_add_msymbol, completion_list_objc_symbol)
	(completion_list_add_fields, add_symtab_completions): Add
	completion_tracker parameter and use it.
	(default_make_symbol_completion_list_break_on_1): Rename to...
	(default_collect_symbol_completion_matches_break_on): ... this.
	Add completion_tracker parameter and use it instead of allocating
	a completion tracker here.
	(default_make_symbol_completion_list_break_on): Delete old
	implementation.
	(default_make_symbol_completion_list): Delete.
	(default_collect_symbol_completion_matches): New.
	(make_symbol_completion_list): Delete.
	(collect_symbol_completion_matches): New.
	(make_symbol_completion_type): Rename to ...
	(collect_symbol_completion_matches_type): ... this.  Add
	completion_tracker parameter and use it instead of VEC.
	(make_file_symbol_completion_list_1): Rename to...
	(collect_file_symbol_completion_matches): ... this.  Add
	completion_tracker parameter and use it instead of VEC.
	(make_file_symbol_completion_list): Delete.
	(add_filename_to_list): Use completion_list instead of a VEC.
	(add_partial_filename_data::list): Now a completion_list.
	(make_source_files_completion_list): Work with a completion_list
	instead of a VEC.
	* symtab.h: Include "completer.h".
	(default_make_symbol_completion_list_break_on)
	(default_make_symbol_completion_list, make_symbol_completion_list)
	(make_symbol_completion_type, make_file_symbol_completion_list)
	(make_source_files_completion_list): Delete.
	(default_collect_symbol_completion_matches_break_on)
	(default_collect_symbol_completion_matches)
	(collect_symbol_completion_matches)
	(collect_symbol_completion_matches_type)
	(collect_file_symbol_completion_matches)
	(make_source_files_completion_list): New.
	* top.c (init_main): Don't install a rl_completion_entry_function
	hook.  Install a rl_attempted_completion_function hook instead.
	* tui/tui-layout.c (layout_completer): Adjust to work with a
	completion_tracker.
	* tui/tui-regs.c (tui_reggroup_completer):
	* tui/tui-win.c (window_name_completer, focus_completer)
	(winheight_completer): Adjust to work with a completion_tracker.
	* value.c: Include "completer.h".
	(complete_internalvar): Adjust to work with a completion_tracker.
	* value.h (complete_internalvar): Likewise.

3 files changed, 22 insertions, 22 deletions

diff --git a/gdb/tui/tui-layout.c b/gdb/tui/tui-layout.c
index e52f789..7ecfaec 100644
--- a/gdb/tui/tui-layout.c
+++ b/gdb/tui/tui-layout.c
@@ -353,14 +353,15 @@ tui_default_win_viewport_height (enum tui_win_type type,
 /* Complete possible layout names.  TEXT is the complete text entered so
    far, WORD is the word currently being completed.  */
 
-static VEC (char_ptr) *
+static void
 layout_completer (struct cmd_list_element *ignore,
+		  completion_tracker &tracker,
 		  const char *text, const char *word)
 {
   static const char *layout_names [] =
     { "src", "asm", "split", "regs", "next", "prev", NULL };
 
-  return complete_on_enum (layout_names, text, word);
+  complete_on_enum (tracker, layout_names, text, word);
 }
 
 /* Function to initialize gdb commands, for tui window layout
diff --git a/gdb/tui/tui-regs.c b/gdb/tui/tui-regs.c
index 3f9a007..c418203 100644
--- a/gdb/tui/tui-regs.c
+++ b/gdb/tui/tui-regs.c
@@ -668,24 +668,23 @@ tui_reg_command (char *args, int from_tty)
 /* Complete names of register groups, and add the special "prev" and "next"
    names.  */
 
-static VEC (char_ptr) *
+static void
 tui_reggroup_completer (struct cmd_list_element *ignore,
+			completion_tracker &tracker,
 			const char *text, const char *word)
 {
-  VEC (char_ptr) *result = NULL;
   static const char *extra[] = { "next", "prev", NULL };
   size_t len = strlen (word);
   const char **tmp;
 
-  result = reggroup_completer (ignore, text, word);
+  reggroup_completer (ignore, tracker, text, word);
 
+  /* XXXX use complete_on_enum instead?  */
   for (tmp = extra; *tmp != NULL; ++tmp)
     {
       if (strncmp (word, *tmp, len) == 0)
-	VEC_safe_push (char_ptr, result, xstrdup (*tmp));
+	tracker.add_completion (gdb::unique_xmalloc_ptr<char> (xstrdup (*tmp)));
     }
-
-  return result;
 }
 
 /* Provide a prototype to silence -Wmissing-prototypes.  */
diff --git a/gdb/tui/tui-win.c b/gdb/tui/tui-win.c
index f49d7d5..e0df667 100644
--- a/gdb/tui/tui-win.c
+++ b/gdb/tui/tui-win.c
@@ -359,12 +359,12 @@ tui_set_var_cmd (char *null_args, int from_tty, struct cmd_list_element *c)
    window names 'next' and 'prev' will also be considered as possible
    completions of the window name.  */
 
-static VEC (char_ptr) *
-window_name_completer (int include_next_prev_p,
+static void
+window_name_completer (completion_tracker &tracker,
+		       int include_next_prev_p,
 		       const char *text, const char *word)
 {
   VEC (const_char_ptr) *completion_name_vec = NULL;
-  VEC (char_ptr) *matches_vec;
   int win_type;
 
   for (win_type = SRC_WIN; win_type < MAX_MAJOR_WINDOWS; win_type++)
@@ -398,39 +398,39 @@ window_name_completer (int include_next_prev_p,
     }
 
   VEC_safe_push (const_char_ptr, completion_name_vec, NULL);
-  matches_vec
-    = complete_on_enum (VEC_address (const_char_ptr, completion_name_vec),
-			text, word);
+  complete_on_enum (tracker,
+		    VEC_address (const_char_ptr, completion_name_vec),
+		    text, word);
 
   VEC_free (const_char_ptr, completion_name_vec);
-
-  return matches_vec;
 }
 
 /* Complete possible window names to focus on.  TEXT is the complete text
    entered so far, WORD is the word currently being completed.  */
 
-static VEC (char_ptr) *
+static void
 focus_completer (struct cmd_list_element *ignore,
-		  const char *text, const char *word)
+		 completion_tracker &tracker,
+		 const char *text, const char *word)
 {
-  return window_name_completer (1, text, word);
+  window_name_completer (tracker, 1, text, word);
 }
 
 /* Complete possible window names for winheight command.  TEXT is the
    complete text entered so far, WORD is the word currently being
    completed.  */
 
-static VEC (char_ptr) *
+static void
 winheight_completer (struct cmd_list_element *ignore,
+		     completion_tracker &tracker,
 		     const char *text, const char *word)
 {
   /* The first word is the window name.  That we can complete.  Subsequent
      words can't be completed.  */
   if (word != text)
-    return NULL;
+    return;
 
-  return window_name_completer (0, text, word);
+  window_name_completer (tracker, 0, text, word);
 }
 
 /* Function to initialize gdb commands, for tui window