Rewrite/enhance explicit locations completer, parse left->right

One of the most annoying (to me) things about GDB's completion is when
you have overloads in your program, and you want to set a breakpoint
in one of them:

 void function(int);  // set breakpoint here.
 void function(long);

 (gdb) b -f func[TAB]
 (gdb) b -f function(       # ok, gdb completed as much as possible.
 (gdb) b -f function([TAB]  # show me the overloads, please.
 <_all_ symbols in the program are shown...>

E.g., when debugging GDB, that'd be:

 (gdb) b -f function([TAB]
 (anonymous namespace)::get_global()::global  pt_insn_get_offset@plt                       scm_new_port_table_entry
 asprintf                                     pt_pkt_alloc_decoder                         scm_new_port_table_entry@plt
 asprintf@plt                                 pt_pkt_alloc_decoder@plt                     scm_out_of_range
 bt_ctf_get_char_array                        pt_pkt_sync_forward                          scm_out_of_range@plt
 bt_ctf_get_char_array@plt                    pt_pkt_sync_forward@plt                      scm_putc
 bt_ctf_get_uint64                            pwrite                                       scm_putc@plt
 bt_ctf_get_uint64@plt                        pwrite@plt                                   scm_reverse_x
 bt_ctf_iter_read_event                       PyErr_Restore                                scm_reverse_x@plt
 bt_ctf_iter_read_event@plt                   PyErr_Restore@plt                            scm_set_port_filename_x
 <snip...>

Now that's a load of completely useless completions.

The reason GDB offers those is that the completer relies on readline
figuring out the completion word point in the input line based on the
language's word break characters, which include "(".  So readline
tells the completer to complete on "", the string that is after '('.
Likewise, if you type "function(i[TAB]" to try to complete to "int",
you're out of luck.  GDB shows you all the symbols in the program that
start with "i"...  This makes sense for the expression completer, as
what you'd want to type is e.g., a global variable, say:

(gdb) print function(i[TAB]

but, it makes no sense when specifying a function name for a
breakpoint location.

To get around that limitation, users need to quote the function name,
like:

 (gdb) b -f 'function([TAB]
 function(int)      function(long)
 (gdb) b 'function(i[TAB]
 (gdb) b 'function(int)' # now completes correctly!

Note that the quoting is only necessary for completion.  Creating the
breakpoint does not require the quoting:

 (gdb) b -f function(int) [RET]
 Breakpoint 1 at ....

This patch removes this limitation.

(
Actually, it's a necessary patch, though not sufficient.  That'll
start working correctly by the end of the series.  With this patch, if try it,
you'll see:

 (gdb) b -f function(i[TAB]
 (gdb) b -f function

i.e., gdb strips everything after the "(".  That's caused by some code
in symtab.c that'll be eliminated further down the series.  These
patches are all unfortunately interrelated, which is also the reason
new tests only appear much later in the series.
But let's ignore that reality for the remainder of the description.
)

So... this patch gets rid of the need for quoting.

It does that by adding a way for a completer to control the exact
completion word point that readline should start the completion
request for, instead of letting readline try to figure it out using
the current language's word break chars array, and often failing.

In the case above, we want the completer to figure out that it's
completing a function name that starts with "function(i".  It now
does.

It took me a while to figure out a way to ask readline to "use this
exact word point", and for a while I feared that it'd be impossible
with current readline (and having to rely on master readline for core
functionality is something I'd like to avoid very much).  Eventually,
after several different attempts, I came up with what is described in
the comment above gdb_custom_word_point_brkchars in the patch.

With this patch, the handle_brkchars phase of the explicit location
completer advances the expected word point as it parses the input line
left to right, until it figures out exactly what we're completing,
instead of expecting readline to break the string using the word break
characters, and then having the completer heuristically fix up a bad
decision by parsing the input string backwards.  This allows correctly
knowning that we're completing a symbol name after -function, complete
functions without quoting, etc.

Later, we'll make use of this same mechanims to implement a proper
linespec completer that avoids need for quoting too.

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

	* ada-lang.c (ada_collect_symbol_completion_matches): Add
	complete_symbol_mode parameter.
	* cli/cli-cmds.c (complete_command): Get the completion result out
	of the handle_brkchars tracker if used a custom word point.
	* completer.c: Include "linespec.h".
	(enum explicit_location_match_type) <MATCH_LINE>: New enumerator.
	(advance_to_expression_complete_word_point): New.
	(completion_tracker::completes_to_completion_word): New.
	(complete_files_symbols): Pass down
	complete_symbol_mode::EXPRESSION.
	(explicit_options, probe_options): New.
	(collect_explicit_location_matches): Complete on the
	explictit_loc->foo instead of word.  Use
	linespec_complete_function.  Handle MATCH_LINE.  Handle offering
	keyword and options completions.
	(backup_text_ptr): Delete.
	(skip_keyword): New.
	(complete_explicit_location): Remove 'word' parameter.  Add
	language, quoted_arg_start and quoted_arg_end parameters.
	Rewrite, parsing left to right.
	(location_completer): Rewrite.
	(location_completer_handle_brkchars): New function.
	(symbol_completer): Pass down complete_symbol_mode::EXPRESSION.
	(enum complete_line_internal_reason): Adjust comments.
	(completion_tracker::discard_completions): New.
	(completer_handle_brkchars_func_for_completer): Handle
	location_completer.
	(gdb_custom_word_point_brkchars)
	(gdb_org_rl_basic_quote_characters): New.
	(gdb_completion_word_break_characters_throw)
	(completion_find_completion_word): Handle trackers that use a
	custom word point.
	(completion_tracker::advance_custom_word_point_by): New.
	(completion_tracker::build_completion_result): Don't rely on
	readline appending the quote char.
	(gdb_rl_attempted_completion_function_throw): Handle trackers that
	use a custom word point.
	(gdb_rl_attempted_completion_function): Restore
	rl_basic_quote_characters.
	* completer.h (class completion_tracker): Extend intro comment.
	(completion_tracker::set_quote_char)
	(completion_tracker::quote_char)
	(completion_tracker::set_use_custom_word_point)
	(completion_tracker::use_custom_word_point)
	(completion_tracker::custom_word_point)
	(completion_tracker::set_custom_word_point)
	(completion_tracker::advance_custom_word_point_by)
	(completion_tracker::completes_to_completion_word)
	(completion_tracker::discard_completions): New methods.
	(completion_tracker::m_quote_char)
	(completion_tracker::m_use_custom_word_point)
	(completion_tracker::m_custom_word_point): New fields.
	(advance_to_expression_complete_word_point): Declare.
	* f-lang.c (f_collect_symbol_completion_matches): Add
	complete_symbol_mode parameter.
	* language.h (struct language_defn)
	<la_collect_symbol_completion_matches>: Add complete_symbol_mode
	parameter.
	* linespec.c (linespec_keywords): Add NULL terminator.  Make extern.
	(linespec_complete_function): New function.
	(linespec_lexer_lex_keyword): Adjust.
	* linespec.h (linespec_keywords, linespec_complete_function): New
	declarations.
	* location.c (find_end_quote): New function.
	(explicit_location_lex_one): Add explicit_completion_info
	parameter.  Save quoting info.  Don't throw if being called for
	completion.  Don't handle Ada operators here.
	(is_cp_operator, skip_op_false_positives, first_of)
	(explicit_location_lex_one_function): New function.
	(string_to_explicit_location): Replace 'dont_throw' parameter with
	an explicit_completion_info pointer parameter.  Handle it.  Don't
	use explicit_location_lex_one to lex function names.  Use
	explicit_location_lex_one_function instead.
	* location.h (struct explicit_completion_info): New.
	(string_to_explicit_location): Replace 'dont_throw' parameter with
	an explicit_completion_info pointer parameter.
	* symtab.c (default_collect_symbol_completion_matches_break_on):
	Add complete_symbol_mode parameter.  Handle LINESPEC mode.
	(default_collect_symbol_completion_matches)
	(collect_symbol_completion_matches): Add complete_symbol_mode
	parameter.
	(collect_symbol_completion_matches_type): Pass down
	complete_symbol_mode::EXPRESSION.
	(collect_file_symbol_completion_matches): Add complete_symbol_mode
	parameter.  Handle LINESPEC mode.
	* symtab.h (complete_symbol_mode): New.
	(default_collect_symbol_completion_matches_break_on)
	(default_collect_symbol_completion_matches)
	(collect_symbol_completion_matches)
	(collect_file_symbol_completion_matches): Add complete_symbol_mode
	parameter.

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

	* gdb.linespec/ls-errs.exp (do_test): Adjust expected output.

15 files changed, 1029 insertions, 165 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index f1e21f1..b341eb1 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,99 @@
 2017-07-17  Pedro Alves  <palves@redhat.com>
 
+	* ada-lang.c (ada_collect_symbol_completion_matches): Add
+	complete_symbol_mode parameter.
+	* cli/cli-cmds.c (complete_command): Get the completion result out
+	of the handle_brkchars tracker if used a custom word point.
+	* completer.c: Include "linespec.h".
+	(enum explicit_location_match_type) <MATCH_LINE>: New enumerator.
+	(advance_to_expression_complete_word_point): New.
+	(completion_tracker::completes_to_completion_word): New.
+	(complete_files_symbols): Pass down
+	complete_symbol_mode::EXPRESSION.
+	(explicit_options, probe_options): New.
+	(collect_explicit_location_matches): Complete on the
+	explictit_loc->foo instead of word.  Use
+	linespec_complete_function.  Handle MATCH_LINE.  Handle offering
+	keyword and options completions.
+	(backup_text_ptr): Delete.
+	(skip_keyword): New.
+	(complete_explicit_location): Remove 'word' parameter.  Add
+	language, quoted_arg_start and quoted_arg_end parameters.
+	Rewrite, parsing left to right.
+	(location_completer): Rewrite.
+	(location_completer_handle_brkchars): New function.
+	(symbol_completer): Pass down complete_symbol_mode::EXPRESSION.
+	(enum complete_line_internal_reason): Adjust comments.
+	(completion_tracker::discard_completions): New.
+	(completer_handle_brkchars_func_for_completer): Handle
+	location_completer.
+	(gdb_custom_word_point_brkchars)
+	(gdb_org_rl_basic_quote_characters): New.
+	(gdb_completion_word_break_characters_throw)
+	(completion_find_completion_word): Handle trackers that use a
+	custom word point.
+	(completion_tracker::advance_custom_word_point_by): New.
+	(completion_tracker::build_completion_result): Don't rely on
+	readline appending the quote char.
+	(gdb_rl_attempted_completion_function_throw): Handle trackers that
+	use a custom word point.
+	(gdb_rl_attempted_completion_function): Restore
+	rl_basic_quote_characters.
+	* completer.h (class completion_tracker): Extend intro comment.
+	(completion_tracker::set_quote_char)
+	(completion_tracker::quote_char)
+	(completion_tracker::set_use_custom_word_point)
+	(completion_tracker::use_custom_word_point)
+	(completion_tracker::custom_word_point)
+	(completion_tracker::set_custom_word_point)
+	(completion_tracker::advance_custom_word_point_by)
+	(completion_tracker::completes_to_completion_word)
+	(completion_tracker::discard_completions): New methods.
+	(completion_tracker::m_quote_char)
+	(completion_tracker::m_use_custom_word_point)
+	(completion_tracker::m_custom_word_point): New fields.
+	(advance_to_expression_complete_word_point): Declare.
+	* f-lang.c (f_collect_symbol_completion_matches): Add
+	complete_symbol_mode parameter.
+	* language.h (struct language_defn)
+	<la_collect_symbol_completion_matches>: Add complete_symbol_mode
+	parameter.
+	* linespec.c (linespec_keywords): Add NULL terminator.  Make extern.
+	(linespec_complete_function): New function.
+	(linespec_lexer_lex_keyword): Adjust.
+	* linespec.h (linespec_keywords, linespec_complete_function): New
+	declarations.
+	* location.c (find_end_quote): New function.
+	(explicit_location_lex_one): Add explicit_completion_info
+	parameter.  Save quoting info.  Don't throw if being called for
+	completion.  Don't handle Ada operators here.
+	(is_cp_operator, skip_op_false_positives, first_of)
+	(explicit_location_lex_one_function): New function.
+	(string_to_explicit_location): Replace 'dont_throw' parameter with
+	an explicit_completion_info pointer parameter.  Handle it.  Don't
+	use explicit_location_lex_one to lex function names.  Use
+	explicit_location_lex_one_function instead.
+	* location.h (struct explicit_completion_info): New.
+	(string_to_explicit_location): Replace 'dont_throw' parameter with
+	an explicit_completion_info pointer parameter.
+	* symtab.c (default_collect_symbol_completion_matches_break_on):
+	Add complete_symbol_mode parameter.  Handle LINESPEC mode.
+	(default_collect_symbol_completion_matches)
+	(collect_symbol_completion_matches): Add complete_symbol_mode
+	parameter.
+	(collect_symbol_completion_matches_type): Pass down
+	complete_symbol_mode::EXPRESSION.
+	(collect_file_symbol_completion_matches): Add complete_symbol_mode
+	parameter.  Handle LINESPEC mode.
+	* symtab.h (complete_symbol_mode): New.
+	(default_collect_symbol_completion_matches_break_on)
+	(default_collect_symbol_completion_matches)
+	(collect_symbol_completion_matches)
+	(collect_file_symbol_completion_matches): Add complete_symbol_mode
+	parameter.
+
+2017-07-17  Pedro Alves  <palves@redhat.com>
+
 	* utils.c (enum class strncmp_iw_mode): New.
 	(strcmp_iw): Rename to ...
 	(strncmp_iw_with_mode): ... this.  Add string2_len and mode
diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
index e629902..9b5dfab 100644
--- a/gdb/ada-lang.c
+++ b/gdb/ada-lang.c
@@ -6500,6 +6500,7 @@ symbol_completion_add (completion_tracker &tracker,
 
 static void
 ada_collect_symbol_completion_matches (completion_tracker &tracker,
+				       complete_symbol_mode mode,
 				       const char *text0, const char *word,
 				       enum type_code code)
 {
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index fb41e24..af750d3 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -266,6 +266,7 @@ complete_command (char *arg_entry, int from_tty)
 
   completion_tracker tracker_handle_brkchars;
   completion_tracker tracker_handle_completions;
+  completion_tracker *tracker;
 
   int quote_char = '\0';
   const char *word;
@@ -275,8 +276,17 @@ complete_command (char *arg_entry, int from_tty)
       word = completion_find_completion_word (tracker_handle_brkchars,
 					      arg, &quote_char);
 
-      /* Completers must be called twice.  */
-      complete_line (tracker_handle_completions, word, arg, strlen (arg));
+      /* Completers that provide a custom word point in the
+	 handle_brkchars phase also compute their completions then.
+	 Completers that leave the completion word handling to readline
+	 must be called twice.  */
+      if (tracker_handle_brkchars.use_custom_word_point ())
+	tracker = &tracker_handle_brkchars;
+      else
+	{
+	  complete_line (tracker_handle_completions, word, arg, strlen (arg));
+	  tracker = &tracker_handle_completions;
+	}
     }
   CATCH (ex, RETURN_MASK_ALL)
     {
@@ -286,8 +296,7 @@ complete_command (char *arg_entry, int from_tty)
   std::string arg_prefix (arg, word - arg);
 
   completion_result result
-    = (tracker_handle_completions.build_completion_result
-       (word, word - arg, strlen (arg)));
+    = tracker->build_completion_result (word, word - arg, strlen (arg));
 
   if (result.number_matches != 0)
     {
diff --git a/gdb/completer.c b/gdb/completer.c
index 196610d..1e4fe18 100644
--- a/gdb/completer.c
+++ b/gdb/completer.c
@@ -29,6 +29,7 @@
 #include "arch-utils.h"
 #include "location.h"
 #include <algorithm>
+#include "linespec.h"
 #include "cli/cli-decode.h"
 
 /* FIXME: This is needed because of lookup_cmd_1 ().  We should be
@@ -44,6 +45,9 @@
 
 #include "completer.h"
 
+static void complete_expression (completion_tracker &tracker,
+				 const char *text, const char *word);
+
 /* Misc state that needs to be tracked across several different
    readline completer entry point calls, all related to a single
    completion invocation.  */
@@ -63,8 +67,9 @@ struct gdb_completer_state
 /* The current completion state.  */
 static gdb_completer_state current_completion;
 
-/* An enumeration of the various things a user might
-   attempt to complete for a location.  */
+/* An enumeration of the various things a user might attempt to
+   complete for a location.  If you change this, remember to update
+   the explicit_options array below too.  */
 
 enum explicit_location_match_type
 {
@@ -74,6 +79,9 @@ enum explicit_location_match_type
     /* The name of a function or method.  */
     MATCH_FUNCTION,
 
+    /* A line number.  */
+    MATCH_LINE,
+
     /* The name of a label.  */
     MATCH_LABEL
 };
@@ -366,6 +374,48 @@ gdb_rl_find_completion_word (struct gdb_rl_completion_word_info *info,
   return line_buffer + point;
 }
 
+/* See completer.h.  */
+
+const char *
+advance_to_expression_complete_word_point (completion_tracker &tracker,
+					   const char *text)
+{
+  gdb_rl_completion_word_info info;
+
+  info.word_break_characters
+    = current_language->la_word_break_characters ();
+  info.quote_characters = gdb_completer_quote_characters;
+  info.basic_quote_characters = rl_basic_quote_characters;
+
+  const char *start
+    = gdb_rl_find_completion_word (&info, NULL, NULL, text);
+
+  tracker.advance_custom_word_point_by (start - text);
+
+  return start;
+}
+
+/* See completer.h.  */
+
+bool
+completion_tracker::completes_to_completion_word (const char *word)
+{
+  if (m_lowest_common_denominator_unique)
+    {
+      const char *lcd = m_lowest_common_denominator;
+
+      if (strncmp_iw (word, lcd, strlen (lcd)) == 0)
+	{
+	  /* Maybe skip the function and complete on keywords.  */
+	  size_t wordlen = strlen (word);
+	  if (word[wordlen - 1] == ' ')
+	    return true;
+	}
+    }
+
+  return false;
+}
+
 /* Complete on linespecs, which might be of two possible forms:
 
        file:line
@@ -450,7 +500,9 @@ complete_files_symbols (completion_tracker &tracker,
      symbols as well as on files.  */
   if (colon)
     {
-      collect_file_symbol_completion_matches (tracker, symbol_start, word,
+      collect_file_symbol_completion_matches (tracker,
+					      complete_symbol_mode::EXPRESSION,
+					      symbol_start, word,
 					      file_to_match);
       xfree (file_to_match);
     }
@@ -458,7 +510,9 @@ complete_files_symbols (completion_tracker &tracker,
     {
       size_t text_len = strlen (text);
 
-      collect_symbol_completion_matches (tracker, symbol_start, word);
+      collect_symbol_completion_matches (tracker,
+					 complete_symbol_mode::EXPRESSION,
+					 symbol_start, word);
       /* If text includes characters which cannot appear in a file
 	 name, they cannot be asking for completion on files.  */
       if (strcspn (text,
@@ -499,10 +553,32 @@ complete_files_symbols (completion_tracker &tracker,
       /* No completions at all.  As the final resort, try completing
 	 on the entire text as a symbol.  */
       collect_symbol_completion_matches (tracker,
+					 complete_symbol_mode::EXPRESSION,
 					 orig_text, word);
     }
 }
 
+/* The explicit location options.  Note that indexes into this array
+   must match the explicit_location_match_type enumerators.  */
+static const char *const explicit_options[] =
+  {
+    "-source",
+    "-function",
+    "-line",
+    "-label",
+    NULL
+  };
+
+/* The probe modifier options.  These can appear before a location in
+   breakpoint commands.  */
+static const char *const probe_options[] =
+  {
+    "-probe",
+    "-probe-stap",
+    "-probe-dtrace",
+    NULL
+  };
+
 /* Returns STRING if not NULL, the empty string otherwise.  */
 
 static const char *
@@ -518,18 +594,22 @@ static void
 collect_explicit_location_matches (completion_tracker &tracker,
 				   struct event_location *location,
 				   enum explicit_location_match_type what,
-				   const char *word)
+				   const char *word,
+				   const struct language_defn *language)
 {
   const struct explicit_location *explicit_loc
     = get_explicit_location (location);
 
+  /* Note, in the various MATCH_* below, we complete on
+     explicit_loc->foo instead of WORD, because only the former will
+     have already skipped past any quote char.  */
   switch (what)
     {
     case MATCH_SOURCE:
       {
 	const char *source = string_or_empty (explicit_loc->source_filename);
 	completion_list matches
-	  = make_source_files_completion_list (source, word);
+	  = make_source_files_completion_list (source, source);
 	tracker.add_completions (std::move (matches));
       }
       break;
@@ -537,18 +617,15 @@ collect_explicit_location_matches (completion_tracker &tracker,
     case MATCH_FUNCTION:
       {
 	const char *function = string_or_empty (explicit_loc->function_name);
-	if (explicit_loc->source_filename != NULL)
-	  {
-	    const char *filename = explicit_loc->source_filename;
-
-	    collect_file_symbol_completion_matches (tracker,
-						    function, word, filename);
-	  }
-       else
-	 collect_symbol_completion_matches (tracker, function, word);
+	linespec_complete_function (tracker, function,
+				    explicit_loc->source_filename);
       }
       break;
 
+    case MATCH_LINE:
+      /* Nothing to offer.  */
+      break;
+
     case MATCH_LABEL:
       /* Not supported.  */
       break;
@@ -556,126 +633,296 @@ collect_explicit_location_matches (completion_tracker &tracker,
     default:
       gdb_assert_not_reached ("unhandled explicit_location_match_type");
     }
+
+  if (tracker.completes_to_completion_word (word))
+    {
+      tracker.discard_completions ();
+      tracker.advance_custom_word_point_by (strlen (word));
+      complete_on_enum (tracker, explicit_options, "", "");
+      complete_on_enum (tracker, linespec_keywords, "", "");
+    }
+  else if (!tracker.have_completions ())
+    {
+      /* Maybe we have an unterminated linespec keyword at the tail of
+	 the string.  Try completing on that.  */
+      size_t wordlen = strlen (word);
+      const char *keyword = word + wordlen;
+
+      if (wordlen > 0 && keyword[-1] != ' ')
+	{
+	  while (keyword > word && *keyword != ' ')
+	    keyword--;
+	  /* Don't complete on keywords if we'd be completing on the
+	     whole explicit linespec option.  E.g., "b -function
+	     thr<tab>" should not complete to the "thread"
+	     keyword.  */
+	  if (keyword != word)
+	    {
+	      keyword = skip_spaces_const (keyword);
+
+	      tracker.advance_custom_word_point_by (keyword - word);
+	      complete_on_enum (tracker, linespec_keywords, keyword, keyword);
+	    }
+	}
+      else if (wordlen > 0 && keyword[-1] == ' ')
+	{
+	  /* Assume that we're maybe past the explicit location
+	     argument, and we didn't manage to find any match because
+	     the user wants to create a pending breakpoint.  Offer the
+	     keyword and explicit location options as possible
+	     completions.  */
+	  tracker.advance_custom_word_point_by (keyword - word);
+	  complete_on_enum (tracker, linespec_keywords, keyword, keyword);
+	  complete_on_enum (tracker, explicit_options, keyword, keyword);
+	}
+    }
 }
 
-/* A convenience macro to (safely) back up P to the previous word.  */
+/* If the next word in *TEXT_P is any of the keywords in KEYWORDS,
+   then advance both TEXT_P and the word point in the tracker past the
+   keyword and return the (0-based) index in the KEYWORDS array that
+   matched.  Otherwise, return -1.  */
 
-static const char *
-backup_text_ptr (const char *p, const char *text)
+static int
+skip_keyword (completion_tracker &tracker,
+	      const char * const *keywords, const char **text_p)
 {
-  while (p > text && isspace (*p))
-    --p;
-  for (; p > text && !isspace (p[-1]); --p)
-    ;
+  const char *text = *text_p;
+  const char *after = skip_to_space_const (text);
+  size_t len = after - text;
+
+  if (text[len] != ' ')
+    return -1;
+
+  int found = -1;
+  for (int i = 0; keywords[i] != NULL; i++)
+    {
+      if (strncmp (keywords[i], text, len) == 0)
+	{
+	  if (found == -1)
+	    found = i;
+	  else
+	    return -1;
+	}
+    }
+
+  if (found != -1)
+    {
+      tracker.advance_custom_word_point_by (len + 1);
+      text += len + 1;
+      *text_p = text;
+      return found;
+    }
 
-  return p;
+  return -1;
 }
 
 /* A completer function for explicit locations.  This function
-   completes both options ("-source", "-line", etc) and values.  */
+   completes both options ("-source", "-line", etc) and values.  If
+   completing a quoted string, then QUOTED_ARG_START and
+   QUOTED_ARG_END point to the quote characters.  LANGUAGE is the
+   current language.  */
 
 static void
 complete_explicit_location (completion_tracker &tracker,
 			    struct event_location *location,
-			    const char *text, const char *word)
+			    const char *text,
+			    const language_defn *language,
+			    const char *quoted_arg_start,
+			    const char *quoted_arg_end)
 {
-  const char *p;
+  if (*text != '-')
+    return;
 
-  /* Find the beginning of the word.  This is necessary because
-     we need to know if we are completing an option name or value.  We
-     don't get the leading '-' from the completer.  */
-  p = backup_text_ptr (word, text);
+  int keyword = skip_keyword (tracker, explicit_options, &text);
 
-  if (*p == '-')
+  if (keyword == -1)
+    complete_on_enum (tracker, explicit_options, text, text);
+  else
     {
-      /* Completing on option name.  */
-      static const char *const keywords[] =
+      /* Completing on value.  */
+      enum explicit_location_match_type what
+	= (explicit_location_match_type) keyword;
+
+      if (quoted_arg_start != NULL && quoted_arg_end != NULL)
 	{
-	  "source",
-	  "function",
-	  "line",
-	  "label",
-	  NULL
-	};
+	  if (quoted_arg_end[1] == '\0')
+	    {
+	      /* If completing a quoted string with the cursor right
+		 at the terminating quote char, complete the
+		 completion word without interpretation, so that
+		 readline advances the cursor one whitespace past the
+		 quote, even if there's no match.  This makes these
+		 cases behave the same:
+
+		   before: "b -function function()"
+		   after:  "b -function function() "
+
+		   before: "b -function 'function()'"
+		   after:  "b -function 'function()' "
+
+		 and trusts the user in this case:
+
+		   before: "b -function 'not_loaded_function_yet()'"
+		   after:  "b -function 'not_loaded_function_yet()' "
+	      */
+	      gdb::unique_xmalloc_ptr<char> text_copy
+		(xstrdup (text));
+	      tracker.add_completion (std::move (text_copy));
+	    }
+	  else if (quoted_arg_end[1] == ' ')
+	    {
+	      /* We're maybe past the explicit location argument.
+		 Skip the argument without interpretion, assuming the
+		 user may want to create pending breakpoint.  Offer
+		 the keyword and explicit location options as possible
+		 completions.  */
+	      tracker.advance_custom_word_point_by (strlen (text));
+	      complete_on_enum (tracker, linespec_keywords, "", "");
+	      complete_on_enum (tracker, explicit_options, "", "");
+	    }
+	  return;
+	}
 
-      /* Skip over the '-'.  */
-      ++p;
+      /* Now gather matches  */
+      collect_explicit_location_matches (tracker, location, what, text,
+					 language);
+    }
+}
 
-      complete_on_enum (tracker, keywords, p, p);
-      return;
+/* A completer for locations.  */
+
+void
+location_completer (struct cmd_list_element *ignore,
+		    completion_tracker &tracker,
+		    const char *text, const char *word_entry)
+{
+  int found_probe_option = -1;
+
+  /* If we have a probe modifier, skip it.  This can only appear as
+     first argument.  Until we have a specific completer for probes,
+     falling back to the linespec completer for the remainder of the
+     line is better than nothing.  */
+  if (text[0] == '-' && text[1] == 'p')
+    found_probe_option = skip_keyword (tracker, probe_options, &text);
+
+  const char *option_text = text;
+  int saved_word_point = tracker.custom_word_point ();
+
+  const char *copy = text;
+
+  explicit_completion_info completion_info;
+  event_location_up location
+    = string_to_explicit_location (&copy, current_language,
+				   &completion_info);
+  if (completion_info.quoted_arg_start != NULL
+      && completion_info.quoted_arg_end == NULL)
+    {
+      /* Found an unbalanced quote.  */
+      tracker.set_quote_char (*completion_info.quoted_arg_start);
+      tracker.advance_custom_word_point_by (1);
     }
-  else
+
+  if (location != NULL)
     {
-      /* Completing on value (or unknown).  Get the previous word to see what
-	 the user is completing on.  */
-      size_t len, offset;
-      const char *new_word, *end;
-      enum explicit_location_match_type what;
-      struct explicit_location *explicit_loc
-	= get_explicit_location (location);
-
-      /* Backup P to the previous word, which should be the option
-	 the user is attempting to complete.  */
-      offset = word - p;
-      end = --p;
-      p = backup_text_ptr (p, text);
-      len = end - p;
-
-      if (strncmp (p, "-source", len) == 0)
+      if (*copy != '\0')
 	{
-	  what = MATCH_SOURCE;
-	  new_word = explicit_loc->source_filename + offset;
+	  tracker.advance_custom_word_point_by (copy - text);
+	  text = copy;
+
+	  /* We found a terminator at the tail end of the string,
+	     which means we're past the explicit location options.  We
+	     may have a keyword to complete on.  If we have a whole
+	     keyword, then complete whatever comes after as an
+	     expression.  This is mainly for the "if" keyword.  If the
+	     "thread" and "task" keywords gain their own completers,
+	     they should be used here.  */
+	  int keyword = skip_keyword (tracker, linespec_keywords, &text);
+
+	  if (keyword == -1)
+	    {
+	      complete_on_enum (tracker, linespec_keywords, text, text);
+	    }
+	  else
+	    {
+	      const char *word
+		= advance_to_expression_complete_word_point (tracker, text);
+	      complete_expression (tracker, text, word);
+	    }
 	}
-      else if (strncmp (p, "-function", len) == 0)
+      else
 	{
-	  what = MATCH_FUNCTION;
-	  new_word = explicit_loc->function_name + offset;
+	  tracker.advance_custom_word_point_by (completion_info.last_option
+						- text);
+	  text = completion_info.last_option;
+
+	  complete_explicit_location (tracker, location.get (), text,
+				      current_language,
+				      completion_info.quoted_arg_start,
+				      completion_info.quoted_arg_end);
+
 	}
-      else if (strncmp (p, "-label", len) == 0)
+    }
+  else
+    {
+      /* This is an address or linespec location.  */
+      if (*text == '*')
 	{
-	  what = MATCH_LABEL;
-	  new_word = explicit_loc->label_name + offset;
+	  tracker.advance_custom_word_point_by (1);
+	  text++;
+	  const char *word
+	    = advance_to_expression_complete_word_point (tracker, text);
+	  complete_expression (tracker, text, word);
 	}
       else
 	{
-	  /* The user isn't completing on any valid option name,
-	     e.g., "break -source foo.c [tab]".  */
-	  return;
+	  /* Fall back to the old linespec completer, for now.  */
+
+	  if (word_entry == NULL)
+	    {
+	     /* We're in the handle_brkchars phase.  */
+	      tracker.set_use_custom_word_point (false);
+	      return;
+	    }
+
+	  complete_files_symbols (tracker, text, word_entry);
 	}
+    }
 
-      /* If the user hasn't entered a search expression, e.g.,
-	 "break -function <TAB><TAB>", new_word will be NULL, but
-	 search routines require non-NULL search words.  */
-      if (new_word == NULL)
-	new_word = "";
+  /* Add matches for option names, if either:
 
-      /* Now gather matches  */
-      collect_explicit_location_matches (tracker, location, what, new_word);
+     - Some completer above found some matches, but the word point did
+       not advance (e.g., "b <tab>" finds all functions, or "b -<tab>"
+       matches all objc selectors), or;
+
+     - Some completer above advanced the word point, but found no
+       matches.
+  */
+  if ((text[0] == '-' || text[0] == '\0')
+      && (!tracker.have_completions ()
+	  || tracker.custom_word_point () == saved_word_point))
+    {
+      tracker.set_custom_word_point (saved_word_point);
+      text = option_text;
+
+      if (found_probe_option == -1)
+	complete_on_enum (tracker, probe_options, text, text);
+      complete_on_enum (tracker, explicit_options, text, text);
     }
 }
 
-/* A completer for locations.  */
+/* The corresponding completer_handle_brkchars
+   implementation.  */
 
-void
-location_completer (struct cmd_list_element *ignore,
-		    completion_tracker &tracker,
-		    const char *text, const char *word)
+static void
+location_completer_handle_brkchars (struct cmd_list_element *ignore,
+				    completion_tracker &tracker,
+				    const char *text,
+				    const char *word_ignored)
 {
-  const char *copy = text;
+  tracker.set_use_custom_word_point (true);
 
-  event_location_up location = string_to_explicit_location (&copy,
-							    current_language,
-							    1);
-  if (location != NULL)
-    complete_explicit_location (tracker, location.get (),
-				text, word);
-  else
-    {
-      /* This is an address or linespec location.
-	 Right now both of these are handled by the (old) linespec
-	 completer.  */
-      complete_files_symbols (tracker, text, word);
-    }
+  location_completer (ignore, tracker, text, NULL);
 }
 
 /* Helper for expression_completer which recursively adds field and
@@ -837,7 +1084,8 @@ symbol_completer (struct cmd_list_element *ignore,
 		  completion_tracker &tracker,
 		  const char *text, const char *word)
 {
-  collect_symbol_completion_matches (tracker, text, word);
+  collect_symbol_completion_matches (tracker, complete_symbol_mode::EXPRESSION,
+				     text, word);
 }
 
 /* Here are some useful test cases for completion.  FIXME: These
@@ -866,10 +1114,24 @@ symbol_completer (struct cmd_list_element *ignore,
 enum complete_line_internal_reason
 {
   /* Preliminary phase, called by gdb_completion_word_break_characters
-     function, is used to determine the correct set of chars that are
-     word delimiters depending on the current command in line_buffer.
-     No completion list should be generated; the return value should
-     be NULL.  This is checked by an assertion.  */
+     function, is used to either:
+
+     #1 - Determine the set of chars that are word delimiters
+	  depending on the current command in line_buffer.
+
+     #2 - Manually advance RL_POINT to the "word break" point instead
+	  of letting readline do it (based on too-simple character
+	  matching).
+
+     Simpler completers that just pass a brkchars array to readline
+     (#1 above) must defer generating the completions to the main
+     phase (below).  No completion list should be generated in this
+     phase.
+
+     OTOH, completers that manually advance the word point(#2 above)
+     must set "use_custom_word_point" in the tracker and generate
+     their completion in this phase.  Note that this is the convenient
+     thing to do since they'll be parsing the input line anyway.  */
   handle_brkchars,
 
   /* Main phase, called by complete_line function, is used to get the
@@ -1003,6 +1265,8 @@ complete_line_internal_1 (completion_tracker &tracker,
       p++;
     }
 
+  tracker.advance_custom_word_point_by (p - tmp_command);
+
   if (!c)
     {
       /* It is an unrecognized command.  So there are no
@@ -1184,6 +1448,24 @@ completion_tracker::completion_tracker ()
 
 /* See completer.h.  */
 
+void
+completion_tracker::discard_completions ()
+{
+  xfree (m_lowest_common_denominator);
+  m_lowest_common_denominator = NULL;
+
+  m_lowest_common_denominator_unique = false;
+
+  m_entries_vec.clear ();
+
+  htab_delete (m_entries_hash);
+  m_entries_hash = htab_create_alloc (INITIAL_COMPLETION_HTAB_SIZE,
+				      htab_hash_string, (htab_eq) streq,
+				      NULL, xcalloc, xfree);
+}
+
+/* See completer.h.  */
+
 completion_tracker::~completion_tracker ()
 {
   xfree (m_lowest_common_denominator);
@@ -1412,12 +1694,27 @@ completer_handle_brkchars_func_for_completer (completer_ftype *fn)
   if (fn == filename_completer)
     return filename_completer_handle_brkchars;
 
+  if (fn == location_completer)
+    return location_completer_handle_brkchars;
+
   if (fn == command_completer)
     return command_completer_handle_brkchars;
 
   return default_completer_handle_brkchars;
 }
 
+/* Used as brkchars when we want to tell readline we have a custom
+   word point.  We do that by making our rl_completion_word_break_hook
+   set RL_POINT to the desired word point, and return the character at
+   the word break point as the break char.  This is two bytes in order
+   to fit one break character plus the terminating null.  */
+static char gdb_custom_word_point_brkchars[2];
+
+/* Since rl_basic_quote_characters is not completer-specific, we save
+   its original value here, in order to be able to restore it in
+   gdb_rl_attempted_completion_function.  */
+static const char *gdb_org_rl_basic_quote_characters = rl_basic_quote_characters;
+
 /* Get the list of chars that are considered as word breaks
    for the current command.  */
 
@@ -1434,6 +1731,27 @@ gdb_completion_word_break_characters_throw ()
   complete_line_internal (tracker, NULL, rl_line_buffer,
 			  rl_point, handle_brkchars);
 
+  if (tracker.use_custom_word_point ())
+    {
+      gdb_assert (tracker.custom_word_point () > 0);
+      rl_point = tracker.custom_word_point () - 1;
+      gdb_custom_word_point_brkchars[0] = rl_line_buffer[rl_point];
+      rl_completer_word_break_characters = gdb_custom_word_point_brkchars;
+      rl_completer_quote_characters = NULL;
+
+      /* Clear this too, so that if we're completing a quoted string,
+	 readline doesn't consider the quote character a delimiter.
+	 If we didn't do this, readline would auto-complete {b
+	 'fun<tab>} to {'b 'function()'}, i.e., add the terminating
+	 \', but, it wouldn't append the separator space either, which
+	 is not desirable.  So instead we take care of appending the
+	 quote character to the LCD ourselves, in
+	 gdb_rl_attempted_completion_function.  Since this global is
+	 not just completer-specific, we'll restore it back to the
+	 default in gdb_rl_attempted_completion_function.  */
+      rl_basic_quote_characters = NULL;
+    }
+
   return rl_completer_word_break_characters;
 }
 
@@ -1468,6 +1786,13 @@ completion_find_completion_word (completion_tracker &tracker, const char *text,
 
   complete_line_internal (tracker, NULL, text, point, handle_brkchars);
 
+  if (tracker.use_custom_word_point ())
+    {
+      gdb_assert (tracker.custom_word_point () > 0);
+      *quote_char = tracker.quote_char ();
+      return text + tracker.custom_word_point ();
+    }
+
   gdb_rl_completion_word_info info;
 
   info.word_break_characters = rl_completer_word_break_characters;
@@ -1509,6 +1834,14 @@ completion_tracker::recompute_lowest_common_denominator (const char *new_match)
     }
 }
 
+/* See completer.h.  */
+
+void
+completion_tracker::advance_custom_word_point_by (size_t len)
+{
+  m_custom_word_point += len;
+}
+
 /* Build a new C string that is a copy of LCD with the whitespace of
    ORIG/ORIG_LEN preserved.
 
@@ -1596,6 +1929,13 @@ completion_tracker::build_completion_result (const char *text,
 
   if (m_lowest_common_denominator_unique)
     {
+      /* We don't rely on readline appending the quote char as
+	 delimiter as then readline wouldn't append the ' ' after the
+	 completion.  */
+      char buf[2] = { quote_char () };
+
+      match_list[0] = reconcat (match_list[0], match_list[0],
+				buf, (char *) NULL);
       match_list[1] = NULL;
 
       /* If we already have a space at the end of the match, tell
@@ -1728,14 +2068,20 @@ completion_result::reset_match_list ()
 static char **
 gdb_rl_attempted_completion_function_throw (const char *text, int start, int end)
 {
-  /* Completers must be called twice.  If rl_point (i.e., END) is at
-     column 0, then readline skips the the handle_brkchars phase, and
-     so we create a tracker now in that case too.  */
-  delete current_completion.tracker;
-  current_completion.tracker = new completion_tracker ();
+  /* Completers that provide a custom word point in the
+     handle_brkchars phase also compute their completions then.
+     Completers that leave the completion word handling to readline
+     must be called twice.  If rl_point (i.e., END) is at column 0,
+     then readline skips the handle_brkchars phase, and so we create a
+     tracker now in that case too.  */
+  if (end == 0 || !current_completion.tracker->use_custom_word_point ())
+    {
+      delete current_completion.tracker;
+      current_completion.tracker = new completion_tracker ();
 
-  complete_line (*current_completion.tracker, text,
-		 rl_line_buffer, rl_point);
+      complete_line (*current_completion.tracker, text,
+		     rl_line_buffer, rl_point);
+    }
 
   completion_tracker &tracker = *current_completion.tracker;
 
@@ -1753,6 +2099,10 @@ gdb_rl_attempted_completion_function_throw (const char *text, int start, int end
 char **
 gdb_rl_attempted_completion_function (const char *text, int start, int end)
 {
+  /* Restore globals that might have been tweaked in
+     gdb_completion_word_break_characters.  */
+  rl_basic_quote_characters = gdb_org_rl_basic_quote_characters;
+
   /* If we end up returning NULL, either on error, or simple because
      there are no matches, inhibit readline's default filename
      completer.  */
diff --git a/gdb/completer.h b/gdb/completer.h
index cf93cf0..40d2f58 100644
--- a/gdb/completer.h
+++ b/gdb/completer.h
@@ -133,6 +133,12 @@ public:
      up in the event the user requests to complete on something vague
      that necessitates the time consuming expansion of many symbol
      tables.
+
+   - The custom word point to hand over to readline, for completers
+     that parse the input string in order to dynamically adjust
+     themselves depending on exactly what they're completing.  E.g.,
+     the linespec completer needs to bypass readline's too-simple word
+     breaking algorithm.
 */
 class completion_tracker
 {
@@ -153,10 +159,52 @@ public:
      LIST.  */
   void add_completions (completion_list &&list);
 
+  /* Set the quote char to be appended after a unique completion is
+     added to the input line.  Set to '\0' to clear.  See
+     m_quote_char's description.  */
+  void set_quote_char (int quote_char)
+  { m_quote_char = quote_char; }
+
+  /* The quote char to be appended after a unique completion is added
+     to the input line.  Returns '\0' if no quote char has been set.
+     See m_quote_char's description.  */
+  int quote_char () { return m_quote_char; }
+
+  /* Tell the tracker that the current completer wants to provide a
+     custom word point instead of a list of a break chars, in the
+     handle_brkchars phase.  Such completers must also compute their
+     completions then.  */
+  void set_use_custom_word_point (bool enable)
+  { m_use_custom_word_point = enable; }
+
+  /* Whether the current completer computes a custom word point.  */
+  bool use_custom_word_point () const
+  { return m_use_custom_word_point; }
+
+  /* The custom word point.  */
+  int custom_word_point () const
+  { return m_custom_word_point; }
+
+  /* Set the custom word point to POINT.  */
+  void set_custom_word_point (int point)
+  { m_custom_word_point = point; }
+
+  /* Advance the custom word point by LEN.  */
+  void advance_custom_word_point_by (size_t len);
+
+  /* Return true if we only have one completion, and it matches
+     exactly the completion word.  I.e., completing results in what we
+     already have.  */
+  bool completes_to_completion_word (const char *word);
+
   /* True if we have any completion match recorded.  */
   bool have_completions () const
   { return !m_entries_vec.empty (); }
 
+  /* Discard the current completion match list and the current
+     LCD.  */
+  void discard_completions ();
+
   /* Build a completion_result containing the list of completion
      matches to hand over to readline.  The parameters are as in
      rl_attempted_completion_function.  */
@@ -185,7 +233,30 @@ private:
      searching too early.  */
   htab_t m_entries_hash;
 
-  /* Our idea of lowest common denominator to hand over to readline.  */
+  /* If non-zero, then this is the quote char that needs to be
+     appended after completion (iff we have a unique completion).  We
+     don't rely on readline appending the quote char as delimiter as
+     then readline wouldn't append the ' ' after the completion.
+     I.e., we want this:
+
+      before tab: "b 'function("
+      after tab:  "b 'function()' "
+  */
+  int m_quote_char = '\0';
+
+  /* If true, the completer has its own idea of "word" point, and
+     doesn't want to rely on readline computing it based on brkchars.
+     Set in the handle_brkchars phase.  */
+  bool m_use_custom_word_point = false;
+
+  /* The completer's idea of where the "word" we were looking at is
+     relative to RL_LINE_BUFFER.  This is advanced in the
+     handle_brkchars phase as the completer discovers potential
+     completable words.  */
+  int m_custom_word_point = 0;
+
+  /* Our idea of lowest common denominator to hand over to readline.
+     See intro.  */
   char *m_lowest_common_denominator = NULL;
 
   /* If true, the LCD is unique.  I.e., all completion candidates had
@@ -213,6 +284,15 @@ extern const char *completion_find_completion_word (completion_tracker &tracker,
 						    const char *text,
 						    int *quote_char);
 
+
+/* Assuming TEXT is an expression in the current language, find the
+   completion word point for TEXT, emulating the algorithm readline
+   uses to find the word point, using the current language's word
+   break characters.  */
+
+const char *advance_to_expression_complete_word_point
+  (completion_tracker &tracker, const char *text);
+
 extern char **gdb_rl_attempted_completion_function (const char *text,
 						    int start, int end);
 
diff --git a/gdb/f-lang.c b/gdb/f-lang.c
index e1184ee..937ebff 100644
--- a/gdb/f-lang.c
+++ b/gdb/f-lang.c
@@ -230,10 +230,11 @@ f_word_break_characters (void)
 
 static void
 f_collect_symbol_completion_matches (completion_tracker &tracker,
+				     complete_symbol_mode mode,
 				     const char *text, const char *word,
 				     enum type_code code)
 {
-  default_collect_symbol_completion_matches_break_on (tracker,
+  default_collect_symbol_completion_matches_break_on (tracker, mode,
 						      text, word, ":", code);
 }
 
diff --git a/gdb/language.h b/gdb/language.h
index 7ce4f7f..75b9438 100644
--- a/gdb/language.h
+++ b/gdb/language.h
@@ -330,6 +330,7 @@ struct language_defn
        symbols whose type has a code of CODE should be matched.  */
     void (*la_collect_symbol_completion_matches)
       (completion_tracker &tracker,
+       complete_symbol_mode mode,
        const char *text,
        const char *word,
        enum type_code code);
diff --git a/gdb/linespec.c b/gdb/linespec.c
index 25ebdca..20ac71d 100644
--- a/gdb/linespec.c
+++ b/gdb/linespec.c
@@ -216,9 +216,9 @@ enum ls_token_type
 };
 typedef enum ls_token_type linespec_token_type;
 
-/* List of keywords  */
-
-static const char * const linespec_keywords[] = { "if", "thread", "task" };
+/* List of keywords.  This is NULL-terminated so that it can be used
+   as enum completer.  */
+const char * const linespec_keywords[] = { "if", "thread", "task", NULL };
 #define IF_KEYWORD_INDEX 0
 
 /* A token of the linespec lexer  */
@@ -400,7 +400,7 @@ linespec_lexer_lex_keyword (const char *p)
 
   if (p != NULL)
     {
-      for (i = 0; i < ARRAY_SIZE (linespec_keywords); ++i)
+      for (i = 0; linespec_keywords[i] != NULL; ++i)
 	{
 	  int len = strlen (linespec_keywords[i]);
 
@@ -421,7 +421,7 @@ linespec_lexer_lex_keyword (const char *p)
 		{
 		  p += len;
 		  p = skip_spaces_const (p);
-		  for (j = 0; j < ARRAY_SIZE (linespec_keywords); ++j)
+		  for (j = 0; linespec_keywords[j] != NULL; ++j)
 		    {
 		      int nextlen = strlen (linespec_keywords[j]);
 
@@ -1714,7 +1714,7 @@ linespec_parse_basic (linespec_parser *parser)
 	      if (token.type != LSTOKEN_NUMBER)
 		unexpected_linespec_error (parser);
 
-	      /* Record the lione offset and get the next token.  */
+	      /* Record the line offset and get the next token.  */
 	      name = copy_token_string (token);
 	      cleanup = make_cleanup (xfree, name);
 
@@ -2451,6 +2451,25 @@ linespec_lex_to_end (char **stringp)
   do_cleanups (cleanup);
 }
 
+/* See linespec.h.  */
+
+void
+linespec_complete_function (completion_tracker &tracker,
+			    const char *function,
+			    const char *source_filename)
+{
+  complete_symbol_mode mode = complete_symbol_mode::LINESPEC;
+
+  if (source_filename != NULL)
+    {
+      collect_file_symbol_completion_matches (tracker, mode,
+					      function, function,
+					      source_filename);
+    }
+  else
+    collect_symbol_completion_matches (tracker, mode, function, function);
+}
+
 /* A helper function for decode_line_full and decode_line_1 to
    turn LOCATION into symtabs_and_lines.  */
 
diff --git a/gdb/linespec.h b/gdb/linespec.h
index f1244c4..d55ba12 100644
--- a/gdb/linespec.h
+++ b/gdb/linespec.h
@@ -184,6 +184,16 @@ extern const char *find_toplevel_char (const char *s, char c);
 
 extern void linespec_lex_to_end (char **stringp);
 
+extern const char * const linespec_keywords[];
+
+/* Complete a function symbol, in linespec mode.  If SOURCE_FILENAME
+   is non-NULL, limits completion to the list of functions defined in
+   source files that match SOURCE_FILENAME.  */
+
+extern void linespec_complete_function (completion_tracker &tracker,
+					const char *function,
+					const char *source_filename);
+
 /* Evaluate the expression pointed to by EXP_PTR into a CORE_ADDR,
    advancing EXP_PTR past any parsed text.  */
 
diff --git a/gdb/location.c b/gdb/location.c
index d711d7b..3238c9a 100644
--- a/gdb/location.c
+++ b/gdb/location.c
@@ -415,13 +415,44 @@ event_location_to_string (struct event_location *location)
   return EL_STRING (location);
 }
 
+/* Find an instance of the quote character C in the string S that is
+   outside of all single- and double-quoted strings (i.e., any quoting
+   other than C).  */
+
+static const char *
+find_end_quote (const char *s, char end_quote_char)
+{
+  /* zero if we're not in quotes;
+     '"' if we're in a double-quoted string;
+     '\'' if we're in a single-quoted string.  */
+  char nested_quote_char = '\0';
+
+  for (const char *scan = s; *scan != '\0'; scan++)
+    {
+      if (nested_quote_char != '\0')
+	{
+	  if (*scan == nested_quote_char)
+	    nested_quote_char = '\0';
+	  else if (scan[0] == '\\' && *(scan + 1) != '\0')
+	    scan++;
+	}
+      else if (*scan == end_quote_char && nested_quote_char == '\0')
+	return scan;
+      else if (*scan == '"' || *scan == '\'')
+	nested_quote_char = *scan;
+    }
+
+  return 0;
+}
+
 /* A lexer for explicit locations.  This function will advance INP
    past any strings that it lexes.  Returns a malloc'd copy of the
    lexed string or NULL if no lexing was done.  */
 
 static gdb::unique_xmalloc_ptr<char>
 explicit_location_lex_one (const char **inp,
-			   const struct language_defn *language)
+			   const struct language_defn *language,
+			   explicit_completion_info *completion_info)
 {
   const char *start = *inp;
 
@@ -431,21 +462,27 @@ explicit_location_lex_one (const char **inp,
   /* If quoted, skip to the ending quote.  */
   if (strchr (get_gdb_linespec_parser_quote_characters (), *start))
     {
-      char quote_char = *start;
+      if (completion_info != NULL)
+	completion_info->quoted_arg_start = start;
 
-      /* If the input is not an Ada operator, skip to the matching
-	 closing quote and return the string.  */
-      if (!(language->la_language == language_ada
-	    && quote_char == '\"' && is_ada_operator (start)))
-	{
-	  const char *end = find_toplevel_char (start + 1, quote_char);
+      const char *end = find_end_quote (start + 1, *start);
 
-	  if (end == NULL)
+      if (end == NULL)
+	{
+	  if (completion_info == NULL)
 	    error (_("Unmatched quote, %s."), start);
-	  *inp = end + 1;
+
+	  end = start + strlen (start);
+	  *inp = end;
 	  return gdb::unique_xmalloc_ptr<char> (savestring (start + 1,
-							    *inp - start - 2));
+							    *inp - start - 1));
 	}
+
+      if (completion_info != NULL)
+	completion_info->quoted_arg_end = end;
+      *inp = end + 1;
+      return gdb::unique_xmalloc_ptr<char> (savestring (start + 1,
+							*inp - start - 2));
     }
 
   /* If the input starts with '-' or '+', the string ends with the next
@@ -486,12 +523,180 @@ explicit_location_lex_one (const char **inp,
   return NULL;
 }
 
+/* Return true if COMMA points past "operator".  START is the start of
+   the line that COMMAND points to, hence when reading backwards, we
+   must not read any character before START.  */
+
+static bool
+is_cp_operator (const char *start, const char *comma)
+{
+  if (comma != NULL
+      && (comma - start) >= CP_OPERATOR_LEN)
+    {
+      const char *p = comma;
+
+      while (p > start && isspace (p[-1]))
+	p--;
+      if (p - start >= CP_OPERATOR_LEN)
+	{
+	  p -= CP_OPERATOR_LEN;
+	  if (strncmp (p, CP_OPERATOR_STR, CP_OPERATOR_LEN) == 0
+	      && (p == start
+		  || !(isalnum (p[-1]) || p[-1] == '_')))
+	    {
+	      return true;
+	    }
+	}
+    }
+  return false;
+}
+
+/* When scanning the input string looking for the next explicit
+   location option/delimiter, we jump to the next option by looking
+   for ",", and "-".  Such a character can also appear in C++ symbols
+   like "operator," and "operator-".  So when we find such a
+   character, we call this function to check if we found such a
+   symbol, meaning we had a false positive for an option string.  In
+   that case, we keep looking for the next delimiter, until we find
+   one that is not a false positive, or we reach end of string.  FOUND
+   is the character that scanning found (either '-' or ','), and START
+   is the start of the line that FOUND points to, hence when reading
+   backwards, we must not read any character before START.  Returns a
+   pointer to the next non-false-positive delimiter character, or NULL
+   if none was found.  */
+
+static const char *
+skip_op_false_positives (const char *start, const char *found)
+{
+  while (found != NULL && is_cp_operator (start, found))
+    {
+      if (found[0] == '-' && found[1] == '-')
+	start = found + 2;
+      else
+	start = found + 1;
+      found = find_toplevel_char (start, *found);
+    }
+
+  return found;
+}
+
+/* Assuming both FIRST and NEW_TOK point into the same string, return
+   the pointer that is closer to the start of the string.  If FIRST is
+   NULL, returns NEW_TOK.  If NEW_TOK is NULL, returns FIRST.  */
+
+static const char *
+first_of (const char *first, const char *new_tok)
+{
+  if (first == NULL)
+    return new_tok;
+  else if (new_tok != NULL && new_tok < first)
+    return new_tok;
+  else
+    return first;
+}
+
+/* A lexer for functions in explicit locations.  This function will
+   advance INP past a function until the next option, or until end of
+   string.  Returns a malloc'd copy of the lexed string or NULL if no
+   lexing was done.  */
+
+static gdb::unique_xmalloc_ptr<char>
+explicit_location_lex_one_function (const char **inp,
+				    const struct language_defn *language,
+				    explicit_completion_info *completion_info)
+{
+  const char *start = *inp;
+
+  if (*start == '\0')
+    return NULL;
+
+  /* If quoted, skip to the ending quote.  */
+  if (strchr (get_gdb_linespec_parser_quote_characters (), *start))
+    {
+      char quote_char = *start;
+
+      /* If the input is not an Ada operator, skip to the matching
+	 closing quote and return the string.  */
+      if (!(language->la_language == language_ada
+	    && quote_char == '\"' && is_ada_operator (start)))
+	{
+	  if (completion_info != NULL)
+	    completion_info->quoted_arg_start = start;
+
+	  const char *end = find_toplevel_char (start + 1, quote_char);
+
+	  if (end == NULL)
+	    {
+	      if (completion_info == NULL)
+		error (_("Unmatched quote, %s."), start);
+
+	      end = start + strlen (start);
+	      *inp = end;
+	      char *saved = savestring (start + 1, *inp - start - 1);
+	      return gdb::unique_xmalloc_ptr<char> (saved);
+	    }
+
+	  if (completion_info != NULL)
+	    completion_info->quoted_arg_end = end;
+	  *inp = end + 1;
+	  char *saved = savestring (start + 1, *inp - start - 2);
+	  return gdb::unique_xmalloc_ptr<char> (saved);
+	}
+    }
+
+  const char *comma = find_toplevel_char (start, ',');
+
+  /* If we have "-function -myfunction", or perhaps better example,
+     "-function -[BasicClass doIt]" (objc selector), treat
+     "-myfunction" as the function name.  I.e., skip the first char if
+     it is an hyphen.  Don't skip the first char always, because we
+     may have C++ "operator<", and find_toplevel_char needs to see the
+     'o' in that case.  */
+  const char *hyphen
+    = (*start == '-'
+       ? find_toplevel_char (start + 1, '-')
+       : find_toplevel_char (start, '-'));
+
+  /* Check for C++ "operator," and "operator-".  */
+  comma = skip_op_false_positives (start, comma);
+  hyphen = skip_op_false_positives (start, hyphen);
+
+  /* Pick the one that appears first.  */
+  const char *end = first_of (hyphen, comma);
+
+  /* See if a linespec keyword appears first.  */
+  const char *s = start;
+  const char *ws = find_toplevel_char (start, ' ');
+  while (ws != NULL && linespec_lexer_lex_keyword (ws + 1) == NULL)
+    {
+      s = ws + 1;
+      ws = find_toplevel_char (s, ' ');
+    }
+  if (ws != NULL)
+    end = first_of (end, ws + 1);
+
+  /* If we don't have any terminator, then take the whole string.  */
+  if (end == NULL)
+    end = start + strlen (start);
+
+  /* Trim whitespace at the end.  */
+  while (end > start && end[-1] == ' ')
+    end--;
+
+  *inp = end;
+
+  if (*inp - start > 0)
+    return gdb::unique_xmalloc_ptr<char> (savestring (start, *inp - start));
+
+  return NULL;
+}
+
 /* See description in location.h.  */
 
 event_location_up
 string_to_explicit_location (const char **argp,
 			     const struct language_defn *language,
-			     int dont_throw)
+			     explicit_completion_info *completion_info)
 {
   event_location_up location;
 
@@ -514,6 +719,14 @@ string_to_explicit_location (const char **argp,
       int len;
       const char *start;
 
+      /* Clear these on each iteration, since they should be filled
+	 with info about the last option.  */
+      if (completion_info != NULL)
+	{
+	  completion_info->quoted_arg_start = NULL;
+	  completion_info->quoted_arg_end = NULL;
+	}
+
       /* If *ARGP starts with a keyword, stop processing
 	 options.  */
       if (linespec_lexer_lex_keyword (*argp) != NULL)
@@ -522,40 +735,68 @@ string_to_explicit_location (const char **argp,
       /* Mark the start of the string in case we need to rewind.  */
       start = *argp;
 
+      if (completion_info != NULL)
+	completion_info->last_option = start;
+
       /* Get the option string.  */
       gdb::unique_xmalloc_ptr<char> opt
-	= explicit_location_lex_one (argp, language);
+	= explicit_location_lex_one (argp, language, NULL);
 
-      *argp = skip_spaces_const (*argp);
+      /* Use the length of the option to allow abbreviations.  */
+      len = strlen (opt.get ());
 
       /* Get the argument string.  */
-      gdb::unique_xmalloc_ptr<char> oarg
-	= explicit_location_lex_one (argp, language);
-      bool have_oarg = oarg != NULL;
       *argp = skip_spaces_const (*argp);
 
-      /* Use the length of the option to allow abbreviations.  */
-      len = strlen (opt.get ());
+      /* All options have a required argument.  Checking for this
+	 required argument is deferred until later.  */
+      gdb::unique_xmalloc_ptr<char> oarg;
+      /* True if we have an argument.  This is required because we'll
+	 move from OARG before checking whether we have an
+	 argument.  */
+      bool have_oarg = false;
+
+      /* Convenience to consistently set both OARG/HAVE_OARG from
+	 ARG.  */
+      auto set_oarg = [&] (gdb::unique_xmalloc_ptr<char> arg)
+	{
+	  oarg = std::move (arg);
+	  have_oarg = oarg != NULL;
+	};
 
-      /* All options have a required argument.  Checking for this required
-	 argument is deferred until later.  */
       if (strncmp (opt.get (), "-source", len) == 0)
-	EL_EXPLICIT (location)->source_filename = oarg.release ();
+	{
+	  set_oarg (explicit_location_lex_one (argp, language,
+					       completion_info));
+	  EL_EXPLICIT (location)->source_filename = oarg.release ();
+	}
       else if (strncmp (opt.get (), "-function", len) == 0)
-	EL_EXPLICIT (location)->function_name = oarg.release ();
+	{
+	  set_oarg (explicit_location_lex_one_function (argp, language,
+							completion_info));
+	  EL_EXPLICIT (location)->function_name = oarg.release ();
+	}
       else if (strncmp (opt.get (), "-line", len) == 0)
 	{
+	  set_oarg (explicit_location_lex_one (argp, language, NULL));
+	  *argp = skip_spaces_const (*argp);
 	  if (have_oarg)
-	    EL_EXPLICIT (location)->line_offset
-	      = linespec_parse_line_offset (oarg.get ());
+	    {
+	      EL_EXPLICIT (location)->line_offset
+		= linespec_parse_line_offset (oarg.get ());
+	      continue;
+	    }
 	}
       else if (strncmp (opt.get (), "-label", len) == 0)
-	EL_EXPLICIT (location)->label_name = oarg.release ();
+	{
+	  set_oarg (explicit_location_lex_one (argp, language, completion_info));
+	  EL_EXPLICIT (location)->label_name = oarg.release ();
+	}
       /* Only emit an "invalid argument" error for options
 	 that look like option strings.  */
       else if (opt.get ()[0] == '-' && !isdigit (opt.get ()[1]))
 	{
-	  if (!dont_throw)
+	  if (completion_info == NULL)
 	    error (_("invalid explicit location argument, \"%s\""), opt.get ());
 	}
       else
@@ -567,11 +808,13 @@ string_to_explicit_location (const char **argp,
 	  return location;
 	}
 
+      *argp = skip_spaces_const (*argp);
+
       /* It's a little lame to error after the fact, but in this
 	 case, it provides a much better user experience to issue
 	 the "invalid argument" error before any missing
 	 argument error.  */
-      if (!have_oarg && !dont_throw)
+      if (!have_oarg && completion_info == NULL)
 	error (_("missing argument for \"%s\""), opt.get ());
     }
 
@@ -581,7 +824,7 @@ string_to_explicit_location (const char **argp,
       && EL_EXPLICIT (location)->function_name == NULL
       && EL_EXPLICIT (location)->label_name == NULL
       && (EL_EXPLICIT (location)->line_offset.sign == LINE_OFFSET_UNKNOWN)
-      && !dont_throw)
+      && completion_info == NULL)
     {
       error (_("Source filename requires function, label, or "
 	       "line offset."));
@@ -639,7 +882,7 @@ string_to_event_location (char **stringp,
 
   /* Try an explicit location.  */
   orig = arg = *stringp;
-  event_location_up location = string_to_explicit_location (&arg, language, 0);
+  event_location_up location = string_to_explicit_location (&arg, language, NULL);
   if (location != NULL)
     {
       /* It was a valid explicit location.  Advance STRINGP to
diff --git a/gdb/location.h b/gdb/location.h
index 7e1f012..58536e0 100644
--- a/gdb/location.h
+++ b/gdb/location.h
@@ -218,20 +218,37 @@ extern event_location_up
   string_to_event_location_basic (char **argp,
 				  const struct language_defn *language);
 
+/* Structure filled in by string_to_explicit_location to aid the
+   completer.  */
+struct explicit_completion_info
+{
+  /* Pointer to the last option found.  E.g., in "b -sou src.c -fun
+     func", LAST_OPTION is left pointing at "-fun func".  */
+  const char *last_option = NULL;
+
+  /* These point to the start and end of a quoted argument, iff the
+     last argument was quoted.  If parsing finds an incomplete quoted
+     string (e.g., "break -function 'fun"), then QUOTED_ARG_START is
+     set to point to the opening \', and QUOTED_ARG_END is left NULL.
+     If the last option is not quoted, then both are set to NULL. */
+  const char *quoted_arg_start = NULL;
+  const char *quoted_arg_end = NULL;
+};
+
 /* Attempt to convert the input string in *ARGP into an explicit location.
    ARGP is advanced past any processed input.  Returns an event_location
    (malloc'd) if an explicit location was successfully found in *ARGP,
    NULL otherwise.
 
-   IF !DONT_THROW, this function may call error() if *ARGP looks like
-   properly formed input, e.g., if it is called with missing argument
-   parameters or invalid options.  If DONT_THROW is non-zero, this function
-   will not throw any exceptions.  */
+   If COMPLETION_INFO is NULL, this function may call error() if *ARGP
+   looks like improperly formed input, e.g., if it is called with
+   missing argument parameters or invalid options.  If COMPLETION_INFO
+   is not NULL, this function will not throw any exceptions.  */
 
 extern event_location_up
   string_to_explicit_location (const char **argp,
-			       const struct language_defn *langauge,
-			       int dont_throw);
+			       const struct language_defn *language,
+			       explicit_completion_info *completion_info);
 
 /* A convenience function for testing for unset locations.  */
 
diff --git a/gdb/symtab.c b/gdb/symtab.c
index b077369..d4e107a 100644
--- a/gdb/symtab.c
+++ b/gdb/symtab.c
@@ -4984,6 +4984,7 @@ add_symtab_completions (struct compunit_symtab *cust,
 void
 default_collect_symbol_completion_matches_break_on
   (completion_tracker &tracker,
+   complete_symbol_mode mode,
    const char *text, const char *word,
    const char *break_on, enum type_code code)
 {
@@ -5004,6 +5005,9 @@ default_collect_symbol_completion_matches_break_on
   int sym_text_len;
 
   /* Now look for the symbol we are supposed to complete on.  */
+  if (mode == complete_symbol_mode::LINESPEC)
+    sym_text = text;
+  else
   {
     const char *p;
     char quote_found;
@@ -5209,10 +5213,11 @@ default_collect_symbol_completion_matches_break_on
 
 void
 default_collect_symbol_completion_matches (completion_tracker &tracker,
+					   complete_symbol_mode mode,
 					   const char *text, const char *word,
 					   enum type_code code)
 {
-  return default_collect_symbol_completion_matches_break_on (tracker,
+  return default_collect_symbol_completion_matches_break_on (tracker, mode,
 							     text, word, "",
 							     code);
 }
@@ -5222,9 +5227,10 @@ default_collect_symbol_completion_matches (completion_tracker &tracker,
 
 void
 collect_symbol_completion_matches (completion_tracker &tracker,
+				   complete_symbol_mode mode,
 				   const char *text, const char *word)
 {
-  current_language->la_collect_symbol_completion_matches (tracker,
+  current_language->la_collect_symbol_completion_matches (tracker, mode,
 							  text, word,
 							  TYPE_CODE_UNDEF);
 }
@@ -5237,10 +5243,12 @@ collect_symbol_completion_matches_type (completion_tracker &tracker,
 					const char *text, const char *word,
 					enum type_code code)
 {
+  complete_symbol_mode mode = complete_symbol_mode::EXPRESSION;
+
   gdb_assert (code == TYPE_CODE_UNION
 	      || code == TYPE_CODE_STRUCT
 	      || code == TYPE_CODE_ENUM);
-  current_language->la_collect_symbol_completion_matches (tracker,
+  current_language->la_collect_symbol_completion_matches (tracker, mode,
 							  text, word, code);
 }
 
@@ -5249,6 +5257,7 @@ collect_symbol_completion_matches_type (completion_tracker &tracker,
 
 void
 collect_file_symbol_completion_matches (completion_tracker &tracker,
+					complete_symbol_mode mode,
 					const char *text, const char *word,
 					const char *srcfile)
 {
@@ -5259,6 +5268,9 @@ collect_file_symbol_completion_matches (completion_tracker &tracker,
 
   /* Now look for the symbol we are supposed to complete on.
      FIXME: This should be language-specific.  */
+  if (mode == complete_symbol_mode::LINESPEC)
+    sym_text = text;
+  else
   {
     const char *p;
     char quote_found;
diff --git a/gdb/symtab.h b/gdb/symtab.h
index 8b975ad..35949f0 100644
--- a/gdb/symtab.h
+++ b/gdb/symtab.h
@@ -1499,22 +1499,37 @@ extern void forget_cached_source_info (void);
 
 extern void select_source_symtab (struct symtab *);
 
+/* The reason we're calling into a completion match list collector
+   function.  */
+enum class complete_symbol_mode
+  {
+    /* Completing an expression.  */
+    EXPRESSION,
+
+    /* Completing a linespec.  */
+    LINESPEC,
+  };
+
 extern void default_collect_symbol_completion_matches_break_on
   (completion_tracker &tracker,
+   complete_symbol_mode mode,
    const char *text, const char *word, const char *break_on,
    enum type_code code);
 extern void default_collect_symbol_completion_matches
   (completion_tracker &tracker,
+   complete_symbol_mode,
    const char *,
    const char *,
    enum type_code);
 extern void collect_symbol_completion_matches (completion_tracker &tracker,
+					       complete_symbol_mode,
 					       const char *, const char *);
 extern void collect_symbol_completion_matches_type (completion_tracker &tracker,
 						    const char *, const char *,
 						    enum type_code);
 
 extern void collect_file_symbol_completion_matches (completion_tracker &tracker,
+						    complete_symbol_mode,
 						    const char *,
 						    const char *,
 						    const char *);
diff --git a/gdb/testsuite/ChangeLog b/gdb/testsuite/ChangeLog
index bd68b63..f1f1ecb 100644
--- a/gdb/testsuite/ChangeLog
+++ b/gdb/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2017-07-17  Pedro Alves  <palves@redhat.com>
+
+	* gdb.linespec/ls-errs.exp (do_test): Adjust expected output.
+
 2017-07-15  Andrew Burgess  <andrew.burgess@embecosm.com>
 
 	* gdb.mi/mi-vla-fortran.exp: Make test names unique.
diff --git a/gdb/testsuite/gdb.linespec/ls-errs.exp b/gdb/testsuite/gdb.linespec/ls-errs.exp
index 1f78ca6..7942f1f 100644
--- a/gdb/testsuite/gdb.linespec/ls-errs.exp
+++ b/gdb/testsuite/gdb.linespec/ls-errs.exp
@@ -167,11 +167,14 @@ proc do_test {lang} {
 	test_break "-source $x -line 3" invalid_file [string trim $x \"']
     }
 
-    # Test that option lexing stops at whitespace boundaries
+    # Test that option lexing stops at whitespace boundaries, except
+    # when lexing function names, where we want to handle setting
+    # breakpoints on e.g., "int template_function<int>()".
     test_break "-source this file has spaces.c -line 3" invalid_file "this"
-    test_break "-function function whitespace" invalid_function "function"
-    test_break "-source $srcfile -function function whitespace" \
-	       invalid_function_f "function" $srcfile
+    test_break "-function ret_type tmpl_function" \
+	invalid_function "ret_type tmpl_function"
+    test_break "-source $srcfile -function ret_type tmpl_function" \
+	       invalid_function_f "ret_type tmpl_function" $srcfile
 
     test_break "-function main -label label whitespace" \
 	       invalid_label "label" "main"
@@ -232,7 +235,12 @@ proc do_test {lang} {
     foreach x {"3" "+100" "-100" "foo"} {
 	test_break "main 3" invalid_function "main 3"
 	test_break "-function \"main $x\"" invalid_function "main $x"
-	test_break "main:here $x" invalid_label "here $x" "main"
+	if {$x == "foo"} {
+	    test_break "main:here $x" unexpected_opt "string" $x
+	} else {
+	    test_break "main:here $x" unexpected_opt "number" $x
+	}
+
 	test_break "-function main -label \"here $x\"" \
 		   invalid_label "here $x" "main"
     }